Chapter XXXI
INDIA-RUBBER: DANGERS INCIDENTAL TO THE USE OF BISULPHIDE OF CARBON AND NAPHTHA
Indiarubber is used in the manufacture of waterproof garments, door-mats, toys for children, insulators of electric wires, tobacco pouches, etc. In the production of these articles large numbers of people find employment. During my visits to indiarubber works in Manchester and London I had several opportunities of observing some of the dangers incidental to the trade.
On entering a waterproof garment manufactory one encounters an extremely pungent vapour, which dries and heats the nose and throat, and is apt to make the eyes run water. This is the fume that comes from naphtha, which is used to dissolve the rubber and to form the dough that is spread as a thin layer by means of a roller machine upon the cloth about to be waterproofed. Both coal tar and mineral naphtha are employed. The vapour of naphtha is extremely irritating, and can be detected over the whole of the factory. The colour of the waterproofed material depends upon the pigment that is employed. If, for example, black is wanted, all that has to be added to the dough, composed of indiarubber and naphtha, is lamp black. The men who feed the roller machines, and who regulate the distribution of the dough upon the cloth, are constantly breathing the irritating atmosphere, but I did not find any special complaint in regard to it from them. It is the girls who work in the overheated and often overcrowded rooms of the factory that suffer most. They are usually very anæmic and complain much of headache. So saturated are they with the fumes of naphtha that even after they have left the factory they still feel the taste of naphtha in their food. In the workrooms these girls are employed rolling and pressing the garments; joining the seams, etc., by rubber dissolved in naphtha. On a winter’s night, when the gas is full ablaze, the air of the workroom is extremely pungent, so that girls are often obliged to leave the room and go into the open air for a short period. The fumes of naphtha are more unpleasant than really dangerous; still there is no doubt that the constant inhalation of these fumes during working hours and the distaste for food thereby created cannot but in time undermine the health of the female worker, and render her more or less unfit for duty.
The dangerous process in the manufacture of indiarubber goods is not that in which naphtha is used, but bisulphide of carbon. In order to render rubber goods capable of withstanding alternations of heat and cold, and of retaining their elasticity in all kinds of weather, they must be vulcanised. The vulcanising agent is either the common flowers of sulphur or a compound of sulphur. When 50 to 60 per cent. of sulphur is added to rubber there is obtained a very hard product known as ebonite. Considerable care has to be taken in using sulphur. If, for example, too much sulphur is added to rubber, the goods become hard; 5 per cent. gives good elasticity. There are various ways of bringing indiarubber goods under the influence of sulphur. It may be done in the primary mixing of the dough, so that all that is subsequently required in the treatment of the waterproofed materials is exposure to a great heat, say 260° F. in a closed oven. Another method is to hang up non-vulcanised waterproofed goods for several hours in a hot stove in which there is a basin containing chloride of sulphur heated over a flame. These processes can scarcely be called dangerous, for they are conducted in closed chambers. The real danger lies in using as the vulcanising agent bisulphide of carbon, to which is often added a small quantity of chloride of sulphur. The bisulphide of carbon has an extremely offensive odour: it is very volatile and highly inflammable, but it is an excellent solvent for caoutchouc. To vulcanise indiarubber goods by means of bisulphide of carbon, the materials are passed through a solution containing about one thousand parts of bisulphide of carbon and from two to ten of chloride of sulphur. The indiarubber is dissolved by the carbon bisulphide and becomes incorporated with the sulphur given up by the chloride.
It is difficult to prevent the nauseating, offensive, and repellent vapour given off by carbon bisulphide penetrating the atmosphere of a workroom even when the room is provided with fans. Fortunately, in some respects, the work is carried on in the top storey of the factory. Here the long webs of cloth coated with indiarubber are vulcanised by being passed through a trough of bisulphide of carbon placed in front of rollers. Escaping at the distal end of the machine the cloth is afterwards hung up to dry. All the time the men are at work in this room they are exposed to the vapour of the bisulphide. Inhalation of the vapour is liable to induce a subacute inflammatory condition of the nerves of the limbs known as peripheral neuritis, in consequence of which men lose the power in their arms and legs. Some of the men whom I examined had been paralysed in their lower extremities, had been off work for several months, and had only slowly regained the use of their limbs. Occasionally men may work as long as three or four years in the bisulphide department without becoming paralysed. Before actually losing the power in their legs the men suffer from inco-ordination; they stagger when walking. The workmen complain of the carbon bisulphide vapour making them drowsy and of their sleep being heavy. After working for a few hours in the vulcanising department, they feel tired and sleepy. Thick or foggy weather rather tends to favour the development of these unpleasant symptoms.
The pernicious effects of bisulphide of carbon are by no means confined to the men. The women and girls who dip very fine indiarubber goods--for example, children’s balloons, tobacco pouches, etc.--into the bisulphide, suffer even more severely than the men. The poisoning shows itself under two forms. In one the symptoms which are slowly developed are dizziness, headache, vomiting, lassitude, and not infrequently paralysis of the arms or legs. Many of the female workers complain of tasting the nauseous bisulphide in their food. The appetite thus becomes impaired. In the other form of poisoning, which may be spoken of as acute, the individual is really intoxicated. Girls have told me that on leaving the factory at night they have simply staggered home, they have even fallen as if drunk, or at the end of a day’s work they have had a splitting headache, and on reaching home have sat down, tired out, and fallen asleep before touching their evening meal. This sleep is heavy and non-refreshing. In the morning they drag themselves to the factory feeling ill and headachy, and, like people who are accustomed to the intemperate use of alcohol, they only get relief and recover their nervous equilibrium by renewed inhalation of the vapour of the bisulphide of carbon. Sad as this state of things is, it is nothing to the extremely violent maniacal condition into which some of the workers, both male and female, are known to have been thrown. Some of them have become the victims of acute insanity, and in their frenzy have precipitated themselves from the top rooms of the factory to the ground. In consequence of bisulphide of carbon being extremely explosive, vulcanisation by means of it has generally to be carried on in rooms, one side of which is perfectly open. This open front is usually protected by iron bars.
Bisulphide of carbon, in addition to causing paralysis of the limbs and an exalted condition of the brain, induces a temporary form of amblyopia, or blindness. Women often suffer from excessive menstruation, and, if pregnant, they may abort. Girls sometimes become hysterical and excited. This form of toxic hysteria, like that in plumbism, often masks a deeper form of bisulphide of carbon poisoning. The individual becomes extremely loquacious; she shouts or sings, becomes very irritable, and may, when in this mood, perpetrate acts that are beyond her control and even beyond her consciousness. Just as in some people, after the excitement of alcoholic intoxication has passed off, there comes a stage of depression, physical and mental, so too after intoxication by bisulphide of carbon there is a period marked by great weakness of mind and body. Prolonged exposure to the vapour of bisulphide induces an enfeeblement of the intelligence that recalls the mental weakness of chronic alcoholic inebriety.
In addition to the risks from naphtha and bisulphide of carbon, indiarubber workers are said to be liable to consumption. Dr Philip of Edinburgh states that within a period of eight years he had under his care in the Hospital for Consumption 70 indiarubber workers, and that 85 per cent. of these suffered from respiratory diseases, the bulk of which was phthisis. His experience as to pulmonary phthisis has not been altogether confirmed by that of medical men elsewhere.
Prevention of Poisoning.--Ventilation of the workrooms is of the first importance. This cannot be secured by open windows alone. Owing to the inflammability of carbon bisulphide no fires and no naked lights are allowed in the workroom. The workpeople complain, therefore, of the cold, and as a consequence cannot but have their vital resistance reduced thereby. The air of this particular part of the factory is redolent of the offensive odour coming from the open troughs and basins. As carbon bisulphide is heavier than the ordinary atmosphere, the artificial means of ventilation that are required are such as shall draw the air of the workroom downwards away from the worker. No young person should be allowed to work in the vulcanisation of indiarubber by means of carbon bisulphide, nor should any adult be allowed to work more than five hours a day--two and a half at a stretch--separated by at least an hour’s interval, which should be spent in the open air, if possible, and away from the factory.
This is a kind of work in which there ought to be alternation of employment. All receptacles containing carbon bisulphide when not in use should be covered. The machines should be provided with down-draught suction fans. During the drying of the vulcanised waterproof goods no person should be allowed to enter the room where these products are hanging unless on business that is absolutely necessary. Naphtha receptacles should, when not in use, be kept covered. No food should be eaten in the bisulphide department, and it should be discouraged also where naphtha is used. Girls say that they sometimes can only eat food in the workrooms, because they do not taste the naphtha there. In the open air the food tastes as though it contained naphtha. Workers in the bisulphide process should be medically examined once a month, and the slightest indication of commencing paralysis or other nervous manifestation should be followed by suspension from work. Five hundred cubic feet of air space should be allowed to each worker.
Poisoning by bisulphide of carbon in its minor form generally disappears on removing the individual from his employment. By many of the workers, particularly girls who are extremely poor and ill-fed, suspension from work would be keenly felt, for to them the loss of the weekly wage is a serious matter. When peripheral neuritis has been induced and causes paralysis, recovery is usually tedious. The patient under these circumstances should be taken to a hospital, where under the influence of good food, rest, electricity, and tonic treatment, health will in most instances be regained.
In the Allgm. Medic. Central Zeitung, 22nd December 1900, Lazarus, a surgeon-dentist, draws attention to a new malady to which workers in gutta-percha are liable. In one year he observed twenty cases of dental caries and necrosis of the jawbone not unlike that met with in lucifer matchmakers, and known as phosphorus necrosis. Those workers, who on entering the factory were already the subjects of decayed teeth and carious stumps, are the most predisposed. With the exception of a young woman, aged 19 years, and who had worked in the factory for only two years all the other females who suffered were from 25 to 35 years of age. While Lazarus recommends a dental examination of the teeth of all the workers before entering a gutta-percha factory, he offers no suggestion as to the probable causes of the necrosis of the jaw in the patients who came under his care for treatment.
THOMAS OLIVER.
Chapter XXXII
THE EFFECTS OF DINITROBENZINE AND OTHER NITRO-SUBSTITUTION PRODUCTS OF THE AROMATIC SERIES ON THE WORKMEN EMPLOYED IN THE MANUFACTURE OF HIGH EXPLOSIVES.
There are about fourteen authorised explosives in use in the United Kingdom, all of which contain, more or less, naphthalene and the aromatic nuclei, benzine, toluene, either singly or combined. These nuclei, when nitrated, form the usual combustible elements in high explosives.
The dinitro compounds of benzine exist in three varieties, ortho, meta, and para. The ordinary commercial form consists almost entirely of metadinitrobenzine, and is generally used in the manufacture of high explosives. This is in some cases mixed with a chlorinated hydrocarbon. The metadinitrobenzine is usually commercially pure, it rarely contains a trace of mononitrobenzine, or the lower oxides of nitrogen. A little free acid is generally found which colours the crystals yellow, and stains the hands of the workmen. It is very sensibly volatile at a temperature of 48° C. At ordinary temperatures it is solid, as are also its isomerides, para and orthonitrobenzine.
The proportions used in the various explosives differ very largely, ranging from 5 to 20 per cent. in the finished explosives. In a smaller number the mono, di, and tri nitrobenzine, toluene, and naphthalene are employed either alone or in combination.
When comparing the poisonous nature of these substances, naphthalene is probably not poisonous, whilst some of the toluene compounds are more poisonous than the benzine.
There is evidence that, generally speaking, the higher the nitration of the aromatic series, the more dangerous these substances are to manipulate.
This is borne out by the following investigations, which we communicated to the Lancet, August 31, 1901:--
“We found that mononitrobenzine when given by the mouth to cats was quite harmless, they seemed rather to thrive and grow fat upon it. Dinitrobenzine is exceedingly poisonous both to men and animals. 1.2 grammes given to a cat by the mouth proved fatal in about three hours. The smallest lethal dose for a cat of 6 lb. in weight, given by the mouth in one dose, was .08 gramme. In another instance .06 gramme given in the same manner was almost fatal. A lethal dose of .09 gramme of dinitrobenzine, when given over a consecutive number of days in divided doses of .04, .02, .01, and .02 gramme, did not cause death.”
“Hypodermically, .04 gramme did not prove fatal to a cat.
“In experimenting upon animals with trinitrobenzine, we found that it was distinctly but not much more poisonous than dinitrobenzine.
“Coming to the toluene group, the administration of mononitrotoluene proved, like its homologue mononitrobenzine, quite inert.
“There is great difference of opinion amongst manufacturers as to whether dinitrotoluene has lethal properties or not. The weight of evidence rather supports the latter view. We are investigating this point (Lancet, August 31, 1901).
“Trinitrotoluene is not poisonous under ordinary use.
“For comparative purposes we injected 50 minims of a 1 per cent. solution of dinitrobenzine into a cat, with a fatal result. We then injected 60 minims of a 1 per cent. solution of trinitrotoluene into another cat, with the result that the only effect appeared to be some slight cyanosis.
“Again, 90 minims of a 1 per cent. solution of dinitrobenzine given hypodermically was quickly fatal to a cat, whilst 90 minims of a 1 per cent. trinitrotoluene proved perfectly innocuous.”
This is a very important practical point, as the susceptibility of man and animals seems closely allied. In some factories the trinitrotoluene has been substituted for dinitrobenzine, with great advantage to the health of the workmen employed.
The oxidising bodies used are the nitrates of ammonium, potassium, and barium. These do not appear to affect the workmen injuriously.
The gases produced by the complete detonation of these high explosives, when well diluted with air, are for all practical purposes harmless.
During the process of the manufacture of these high explosives an intimate mixture of the organic compound with the oxidising body results. This is effected in the case of chlorinated metadinitrobenzine (of which this article chiefly treats), by the processes of grinding, melting at a temperature of 98.9° C., cooling, mixing in a closed, heated, jacketed pan at a temperature of 80° C., and finally filling in air-tight cartridges.
Poisonous Dose.--Dinitrobenzine is a potent poison, whether introduced into the stomach, injected into the circulation, absorbed as it readily is by the skin, or inhaled in the form of vapour.
The poisonous dose of dinitrobenzine for an animal, cat, or dog of six pounds in weight averages about .08 gramme; in the same proportion for a man of ten stones weight, it will be about 1.84 grammes.
Dixon Mann (Forensic Medicine, 2nd edition) and T. Oliver (article in Allbutt’s System of Medicine, vol. ii.) do not mention the poisonous dose, but in all probability a dose of under 1 gramme by the mouth will be lethal.
In fatal cases death takes place within twenty-four hours from a single dose. If animals live beyond that time, there is a strong probability of their ultimate recovery.
A marked characteristic of dinitrobenzine is the ease and rapidity with which, when mixed with fat, it passes through the skin into the system. We found that a 25 per cent. ointment in lanoline, rubbed into the skin of a cat, caused death in twenty-four hours, and 400 milligrammes of lanoline containing .1 gramme of dinitrobenzine, when rubbed into the groins of a man, produced lividity, cyanosis, and other pathognomonic symptoms in a few hours. No doubt the secretions of the cutaneous glands facilitate absorption when the powder settles on the skin. It is probable that all the nitro derivatives of the aromatic series pass readily through the skin. In most works, handling any of these crude compounds for any length of time without gloves is prohibited, being considered dangerous.
The concentrated vapour is dangerous in small doses, and fatal in large. A workman breathing for ten minutes the air in a flue through which pure dinitrobenzine had passed from the mixing pans, died from the effects eighteen hours later.
Judging from experiments upon animals, the poisonous dose, if injected hypodermically, is about half that taken by the mouth.
Poisoning divides itself naturally into acute, subacute, and chronic.
Acute Poisoning.--Fatal acute cases are rare, and have been noted chiefly on account of their interest from a medico-legal point of view. The symptoms are nausea and vomiting, intense congestive headache, faintness and giddiness, loss of control over the limbs, numbness, tingling in tongue and lips, and other subjective sensations. A characteristic symptom is deep cyanosis; lips, fingers, and tongue are deeply cyanosed, nearly black in the early stage. The skin becomes cold and clammy, the pulse quick and weak, often over 120 a minute. It is small, thready, and feeble, and shows a very low condition of arterial tension. The capillaries are freely dilated, and cause the line of descent in sphygmographic tracings to be very rapid. In all severe cases the pulse is fully dicrotic, and displays well the loss of vasomotor tone, which is one of the most marked features in these cases. The heart’s action is easily excited by exertion, the breathing is laboured, and the urine darkened. The eyes become bright and glassy, the features pale and ghastly, and coma supervenes, which lasts for many hours. Exceptional symptoms are noises in the head, or dark specks floating before the eyes. When larger doses of the poison have been absorbed, unconsciousness may become complete. The eyes then roll slowly from side to side, the pupils are widely dilated, and the conjunctivæ are insensitive to touch. Both the deep and superficial reflexes are in abeyance. The respirations are increased to even double the normal number, become irregular, and Cheyne-Stokes in character. The limbs become quite flaccid, or one or more of the joints remain stiff, and when this is the case it is usually those of the upper limbs. Eventually this stiffness entirely disappears. The hands, feet, and face become remarkably bloodless. Occasionally there is œdema of the lips and eyelids, or dropsy of the lower extremities. The temperature ranges from 99° F. to 102° F. (Lancet, November 1, 1902, p. 89).
Subacute Poisoning.--Subacute attacks may supervene upon chronic poisoning, in which, besides the usual chronic conditions to be mentioned later, we find a distinct distaste for food, especially breakfast. Sometimes there is nausea, or there may be slight vomiting. This should always be a warning sign, for, if neglected, coma may follow.
The attacks vary in severity according to the amount of the poison absorbed. The symptoms noticed are:--Headache, with throbbing of the temples and forehead, great langour and depression, the urine becomes darkened in colour, the hands moist; there is drowsiness, with great tendency to sleep; the men say it is impossible to keep awake. During the night they sleep soundly unless prevented by an incessant headache. In the morning they awake unrefreshed and heavy. The tongue is fairly clean though dark in colour, and develops a yellowish fur; dull, heavy pains are felt in the back. Breathing is quick and short, and fatigue follows upon the least exertion. Pricking, tingling, and numbness in the extremities are complained of when walking; workmen when so affected may take three hours to cover as many miles; they stagger, do not know where their legs are, frequently fall, and are unable to pick themselves up readily. When asked to walk backwards with their eyes closed, their movements are very unsteady. These symptoms practically disappear if the men leave work a few days; after such rest they say they feel in excellent health and spirits.
Chronic Poisoning.--The more common manifestations may be denominated chronic, as they are found after prolonged absorption of small doses of the poison, and many of them persist for a long time, at least many months, even after the workmen have left this special occupation. All workers who are brought into intimate contact with this poison show more or less the following:--
Upon careful examination of the cases, it is found that those employed suffer from a very severe form of anæmia. The ruddy hue of health disappears; the skin becomes dirty yellow-greyish in colour. This duskiness gradually deepens with the amount of poison absorbed, and decreases as it becomes eliminated. This objective symptom is especially marked in the mucous membrane. The men appear to be suffering from partial asphyxia. The conjunctivæ show a jaundiced tinge.
Muscular System.--The effects of the poison are shown in a marked manner upon the muscular system. The men have not the appearance of being employed in manual labour. When stripped the muscles are seen to be flaccid and the skin loose. The body lacks fullness and firmness. All movements lose tone and precision. Fatigue quickly follows muscular exertion.
In long-continued cases the objective symptoms are occasionally remarkable, such as wasting of the muscles, especially those of the extremities. This has been particularly pointed out by Dr Ross (Medical Chronicle, May 1889). “The muscles of the hands are seen to be very much atrophied. The spaces between the metacarpal bones are more distinctly marked than is normal, and the grooves between them very noticeable. The muscles of the thenar and hypo-thenar eminences are soft and distinctly wasted, especially the abductor indices. Patients cannot, without considerable trouble and difficulty, cause the tips of the thumb and little finger to meet. Sometimes this is more observable in one hand than the other. The phalangeal joints must be bent, otherwise there is inability to flex the thumb strongly into the palm, and at the same time the power of adduction is feeble.
“All the finer and more delicate movements of the hands are greatly restricted in severe cases. Small objects such as pins and needles cannot be readily felt or held. The act of walking loses much of its elasticity and spring, and in consequence the balance of the body is with difficulty maintained. The big toe in the advancing foot does not manifestly drop; it is only slightly flexed into the sole. There is usually no ankle drop, and the power of raising the toes whilst the foot is flat on the ground is not lost. The symptoms of weakness and paresis observed in the muscles of the foot are not so well-marked as those seen in the hand.”
Nervous Symptoms.--Pains of a shooting, stabbing, or darting character are of very frequent occurrence. They are felt in all parts of the body, a common position being under the heart or in the armpit, neck, or jaws. The legs are rarely affected. When the pains are in the locality of the stomach they are of a griping nature. Sometimes a smarting or burning sensation is described, which is felt in the cheeks, forehead, and eyes, or restricted to the soles of the feet. These sensations are not accompanied by tenderness to the touch.
More or less irritation of the peripheral nerves is always present. It shows itself by tingling and itching of the skin of the fingers, palms, and backs of the hands, sometimes extending to the wrists. In a certain proportion of cases they are felt in the feet as well as the hands. They may be restricted to the feet, and only noticed when the men have their boots on, or their legs crossed. Whilst sitting, or at rest in bed, the pains are often acute. They are invariably confined to the dorsum of the foot, never being felt in the soles, and disappear upon standing or walking. Occasionally these symptoms are more severe in the extremity or extremities of one side of the body.
Hyperæsthesia is a most characteristic feature in all these chronic cases of poisoning. In all cases it is present, but it varies both in intensity and in the part of the body affected. It may be felt in one or both feet, restricted to the upper or under surfaces of the toes. Striking the outside, or dorsum of the foot, causes severe electric-like pains to run all over the leg. In a well-marked case there will be exceeding tenderness upon the slightest pressure on any part of the foot. Drawing the finger very gently over these sensitive areas sends shooting pains about four inches up the legs. The soles of the feet are not affected by a light touch, but a sharp blow, tap, or jar, or a false step in walking causes painful sensations as high as the knees. These symptoms are usually more acute in the left than the right leg. The upper extremity is in like manner affected; a gentle rub on a small part of the cutaneous distribution of the ulnar nerve will produce general formication and tingling all over the arm. Partial hemianæsthesia, with a small patch excessively tender, may be present. This is probably hysterical. Dr Dreschfeld points out that Charcot, Balmskz, and Marie have found this same symptom in bisulphide of carbon poisoning, viz., hemianæsthesia with small circumscribed hyperæsthetic areas. The nerve trunks of the legs or arms are sensitive to pressure where superficial; and great pain is caused all over the area of distribution of the occipital nerve by pressure on the nerve trunk.
The muscles are often very tender, especially those of the upper arm. Touch is often impaired in the fingers and toes. Patients almost invariably complain that the skin of the hands and soles of the feet is less sensitive than is usual in the healthy state. The fingers are numb and act clumsily, while the hands feel as if they were gloved. The impression of sand or snow is conveyed to the feet when standing or walking. Heat and cold are with difficulty differentiated. In one sufferer two test-tubes containing water, differing 10 degrees in temperature, being applied to the arms and trunk, were readily distinguished, but from the hips downwards the patient was utterly unable to discover which of the two tubes was the hotter. If applied simultaneously about three inches apart, both were experienced as cold. Generally speaking the skin of the body is more sensitive than that of the limbs, but in all parts variations occur. Upon using a Faradic current of a given strength, which was with difficulty borne by the thighs, arms, and trunk, there was no perceptible impression produced in the calves or legs. In these situations the compasses must be separated three inches, to be distinguished as two points. The transmission of touch and pain are slower than normal, or at any rate are not as readily responded to as in health. The extremities become very quickly chilled. On the slightest exposure to a low temperature the fingers look pale, bloodless, and feel as if they were dead, and the feet are always cold. Hearing and taste are unaffected. There is great loss of energy. Feebleness, lassitude, and depression are invariable concomitants. The sexual appetite is notoriously weakened, or lost, and erections of the penis rare. The reflexes, superficial and deep, are very variable; sometimes they are exaggerated; this, however, is not usual. Generally speaking, they are enfeebled. Dr Reynolds mentions a case where the patient was comatose and the knee-jerk persistent. Cremasteric and plantar reflexes are those most commonly absent. The muscles react readily to a moderate Faradic current, but different groups of muscles vary in their sensitiveness to the same strength of current.
Eye Affections.--Dinitrobenzine produces a distinct toxic defect of vision similar in many respects to that caused by tobacco, iodoform, bisulphide of carbon, etc. This amblyopia will be found in a varying degree in all those who suffer periodically from subacute attacks of poisoning, or who develop other symptoms due to the continued absorption of the poison. Susceptibility may aggravate the symptoms, but no worker can claim perfect immunity. Comparatively few complain of any impairment to their sight, but probably about one in ten are unknowingly affected. Dr Neiden (Edinburgh Medical Journal, 1889) and Mr Simeon Snell (British Medical Journal, 1894) have described the eye affections. The latter summarises his conclusions as follows:--“Failure of sight, often to a considerable degree in both eyes, concentric contraction of the visual field, with in many cases a central colour scotoma, some blurring, never extensive, of the edges of the disc, and a varying degree of pallor of its surface.”
In all cases absence from the work removes these symptoms in a varying length of time: and usually a restricted exposure will alleviate them.
Urinary Affection.--In cases of long-continued chronic poisoning, dinitrobenzine will always be found free in the urine (Dixon Mann). In the urine of animals, tube casts, brown flakes, and hæmoglobin have been isolated, and in the kidneys much cloudy swelling of the epithelium lining the tubules can be seen (Strassmann and Strecker).
We tested the blood, lungs, liver, spleen, and urine from several cats poisoned by dinitrobenzine. In only one sample, the urine from a cat which died from chronic poisoning, could any indication be found. Both sugar and albumen are generally absent. The source of the bile pigments is the hæmoglobin of the blood, and the excretion of these pigments points to the existence of some cause at work in the blood leading to the destruction of hæmoglobin. The large deposit of urates, high specific gravity and presence of biliary pigments found in the urine, is strong corroborative evidence of an active destruction of blood corpuscles.
No experimental evidence has yet proved that reduction takes place in the body in case of the nitro-compounds of benzine to aniline, or phenylene-diamine.
In several samples of urine tested, both nitrates and nitrites were present, so that in the case of phenylene-diamine being present, the pigment Bismarck brown would be formed, and would give the urine a brown tint.
The samples of urine were tested for free dinitrobenzine by the following method: The urine is treated with zinc and hydrochloric acid for some hours. Any dinitrobenzine that may be present is reduced by the nascent hydrogen into phenylene-diamine. The urine is then alkalised with caustic soda, and well shaken up with ether. The ether is then separated, filtered, and evaporated. The residue is treated with dilute acetic acid and nitrite of soda, when a yellow or brown coloration shows the presence of dinitrobenzine in the original sample. In three cases a slight indication was found.
By ordinary reducing agents in the laboratory, such as nascent hydrogen, the nitro-substitution compounds of benzine can easily be reduced as follows:--
Mononitrobenzine to aniline.
Dinitrobenzine to phenylene-diamine.
Trinitrobenzine to triamidobenzine.
The amount of urea is generally high, due to increased metabolism of the tissues.
The exact chemical changes which take place in the body are extremely difficult to follow. The nitro-compounds probably pass through the body without suffering any change, or they may be reduced in the body.
It will be noticed in the subsequent table that all the samples are acid, many being strongly so. Nearly all are dark-brown in colour and generally precipitate a red deposit, principally urates. In most of these urobilin is present, and can be easily recognised by the following test: 100 c.c. of the urine are acidified with 10 drops of strong hydrochloric acid, and then shaken with 20 c.c. of chloroform. The chloroform which falls to the bottom is separated by means of a separating funnel, and filtered into a test-tube, .4 c.c. of a solution of 1 gramme of crystallised acetate of zinc dissolved in a litre of 95 per cent. alcohol is then poured gently down the side of the test-tube, and at the junction where the liquids meet, a green fluorescent ring, characteristic of urobilin, will appear; the solution on shaking will become fluorescent, being green by transmitted, and rose-coloured by reflected light. This pigment can also be detected by means of the spectroscope.
Urine.--In severe cases of dinitrobenzine poisoning, the urine becomes of a dark, tawny, port-wine colour. There is no irritation or frequency in making water.
The following table represents the examination of the urine from very mild cases, such as can any day be found amongst men handling, or breathing the fumes of dinitrobenzine.
Pathology: The Blood.--Active metabolism takes place at once upon contact of the blood tissue with dinitrobenzine, and this may induce a febrile rise of temperature. The blood becomes thin and dark in colour, varying from chocolate-brown to black. The number of blood corpuscles is greatly diminished, in some cases less than half the normal number. The amount of hæmoglobin averages 35 per cent. MacMunn describes the presence of large coloured megalocytes, 12 µ in diameter; the ordinary red corpuscles are smaller than normal, about 5 µ or 6 µ in diameter; many are crenated and broken up.
Haldane (Journal of Physiology, vol. xxi., 1897), in carefully conducted experiments on mice, “finds spectroscopically a feebly-marked band in the red besides the oxyhæmoglobin bands; but it was not methæmoglobin. Methæmoglobin is contained in the blood, but some other pigment is probably present.” In men we were able to obtain the oxyhæmoglobin band, but it was always blurred. Whether there is a special dinitro band in the blood is a disputed point; it has been investigated in animals by Huber and Röhl (Über akute u. chron. Intox durch Nitrokorp d. Benzolreihe, 1890).
URINARY ANALYSIS
+---+-------------+----------------+-----------+-----------+ |No.| Sp. Gr. | Appearance. | Colour. |Reaction to| | |Water = 1000.| | | Litmus. | +---+-------------+----------------+-----------+-----------+ | 1 | 1029 | Clear | Red brown | Acid | | 2 | 1030 | Clear | Yellow | Acid | | 3 | 1024 |Slight pp. mucus| Yellow | Acid | | 4 | 1021 |Slight pp. mucus| Red brown | Acid | | 5 | 1025 | Heavy red pp. | Red brown | Acid | | 6 | 1027 | Clear | Red brown | Acid | | 7 | 1026 |Thick white pp. |Pale yellow| Acid | | 8 | 1026 | Red deposit | Red brown | Acid | | 9 | 1022 | Red deposit | Red brown | Acid | |10 | 1022 | Clear | Yellow | Acid | |11 | 1027 | Red deposit | Red brown | Acid | |12 | 1025 | Red deposit | Red brown | Acid | |13 | 1024 | Red deposit | Red brown | Acid | +---+-------------+----------------+-----------+-----------+
2. of table
+---+-------------+---------+--------+---------+-------+---------+--------------+ |No.| Sp. Gr. | Urea |Albumen.| Bile |Sugar. |Urobilin.|Dinitrobenzol.| | |Water = 1000.|per cent.| |Pigments.| | | | +---+-------------+---------+--------+---------+-------+---------+--------------+ | 1 | 1029 | 2.6 | Nil | Nil | Nil | Nil | Nil | | 2 | 1030 | ... | ... | ... |Present| ... | Nil | | 3 | 1024 | ... | Nil | Nil | Nil | Nil | Nil | | 4 | 1021 | ... | Nil | Nil | Nil | Nil | Nil | | 5 | 1025 | ... | Nil | Nil | Nil | Present | Trace | | 6 | 1027 | 3.3 | Nil | Nil | Nil | Nil | Faint trace | | 7 | 1026 | 2.9 | Nil | Nil | Nil | Nil | Faint trace | | 8 | 1026 | 3.1 | Nil | Nil | Nil | Present | Nil | | 9 | 1022 | 3.0 | Nil | Nil | Nil | Present | Nil | |10 | 1022 | 2.8 | Nil | Nil | Nil | Nil | Nil | |11 | 1027 | 3.1 | Trace | Trace | Nil | Present | Nil | |12 | 1025 | 2.9 | Nil | Nil | Nil | Present | Nil | |13 | 1024 | 2.8 | Nil | Nil | Nil | Present | Nil | +---+-------------+---------+--------+---------+-------+---------+--------------+
Dinitrobenzine is a powerful narcotic poison. Death in acute cases is due to coma in man. Convulsions are frequently and generally observed in animals. It is a powerful disintegrator of the blood, and in dogs, cats, and rabbits causes oligocythemia, poikilocytosis, and hæmoglobinæmia. So great is the destruction of the blood corpuscles that Haldane attributes all the symptoms to the want of oxygen consequent on changes in the blood. In chronic poisoning men exhibit the features of a peripheral neuritis, although this point has not been confirmed by pathological investigation. Strassmann and Strecker (Friedreich’s Blätter für gerichtliche Medizin, 1896), in dogs, have obtained, by staining, degeneration of the lateral columns of the cord. They also found irritation and catarrh of the stomach and intestines, and after large doses small extravasations of broken-down blood-clot, with swelling and cloudiness of the mucous membrane of the stomach. There is also evidence of much tissue degeneration in the organs, probably fatty. In men, post-mortem, we find that the lividity entirely disappears, the skin becomes pale, and all the internal organs, such as the heart, lungs, and liver, are of a pale yellowish cast, and more friable than usual. The brain is of a dull pink colour, and the veins of the body, and especially the meninges, are filled with a thin, characteristically-fluid, black blood.
Prognosis.--Prognosis in cases of poisoning by dinitrobenzine depends upon the amount absorbed, the time the men have been exposed to it, and their previous health. The headache and general malaise caused by small doses are usually recovered from in the course of a few days. A week’s absence from work enables the men to regain their usual energy, the appetite and urine becoming normal. Anæmia is a very persistent trouble. If the number of blood corpuscles becomes greatly decreased, it takes months to restore them. The peculiar dusky colour of the skin can be detected by those who are conversant with this symptom, even weeks after ceasing work. In cases of coma hours may elapse before consciousness returns. Recovery has taken place after insensibility lasting eight to twelve hours. In one fatal case consciousness returned after nearly sixteen hours’ insensibility, but death suddenly occurred half-an-hour afterwards, when the man was being raised quickly and carelessly from the recumbent position. Cases which are going to terminate fatally usually do so within twenty-four hours. Some months may elapse before muscular power is fully restored. The profound anæmia does not leave its mark permanently, it is eventually entirely recovered from when the workers are removed to other occupations. Workmen often affirm that after a time they become accustomed to the effect of the poison. This is not so, any more than individuals can become habituated to taking alcohol without being affected by it. In the early stages of employment the workers notice and complain of the effects of the poison, as it is new and strange to them; eventually they come to regard the symptoms as necessary to the work, and if slight, know from their own experience that, by more care in the manipulation, or absence from work, the symptoms will pass away. Any natural weakness is liable to be aggravated, and pre-existing anæmia will be made worse.
Precautions.--With ordinary care the work is but slightly harmful, but without care it becomes immediately dangerous. The higher the percentage of dinitrobenzine used the greater the risk and the necessity for care. The dinitrobenzine used should be, as far as possible, chemically pure. We find a small admixture of mononitrobenzine makes it more dangerous to manipulate (Lancet, August 31, 1901). Commercial dinitrobenzine is a deadly poison, however introduced into the system. All precautions have for their object the prevention of poisonous quantities gaining access to the system, by the dilution of the poison, and the avoidance of personal contact. Works should be situated in the country. At the erection of the different houses, much attention should be given to their construction and arrangement. Each should be well isolated; not opening one into the other, nor contiguous to another building. Each should be surrounded by a plentiful air space, and have ample ventilation. Every house should be provided with a lantern roof, containing rain-proof windows easily opened and closed. The window space must be ample, and all windows capable of being freely opened or entirely taken out. It is often necessary to regulate the draught, and on windy days removing the windows on the lee side will permit a free current of air, and ample exit of the fumes, dust, and heat generated. No house should be overcrowded with machinery, and the different processes should be conducted as far as possible in separate buildings. All vessels, melting pots, cooling trays, or pans containing a heated compound must be provided with efficient and well-fitting covers, with flues leading from them to the outside air. The floors, tables, covers of pans, ledges, canisters, etc., in all the houses are to be kept clean and free from dust, the powdered compound, and manufactured explosive; and no utensils or useless articles are to be allowed in the houses. Canisters containing the powder must be kept closed with a well-fitting lid. No flue through which heated vapour has passed may be entered by any person. The cleaning of such flues must be done automatically, or from the outside of the building. Cooling trays should be in a shed open on all sides to the external air. A house, or other shelter from the weather, should be provided for the workmen to retire from the vitiated atmosphere of the house whilst watching the operations.
Wherever possible, the processes of grinding, filling, and emptying utensils, hoppers, pans, and cartridges should be done automatically. If done by hand, respirators should be used, and the men should be careful to stand on the windward side of the pans when the covers are off. Washing appliances should be freely supplied, preferably near each house. Towels inside the houses are objectionable; even if covered up they remain wet. Frequent washing of the hands with soap and nail-brushes is most desirable. The face, beard, and head should be kept clean, frequently washed, and free from dust. The beard, hair, and nails should be cut short. The air in the houses should be kept as dry as possible. Moisture in the atmosphere is always followed by an increase in sickness. Low temperature and dry atmosphere cause a proportionate decrease in the sick-rate. This is accounted for by the fact, that moisture makes the powder cling to the exposed parts of the body; perspiration has the same effect, as also some of the deliquescent salts used. In winter the number of invalids is very small, but during the hot summer months is greatly increased. In all houses where there is much dust, respirators are essential. They are of no use against the vaporised fumes. Cotton respirators fitting over the nose and mouth, kept very clean and frequently renewed, are least objected to by the workmen. Dr Snell has suggested a diving-bell apparatus. Gloves are necessary when handling the material. The importance of keeping the interior of the gloves scrupulously clean and tight at the wristbands is self-evident.
Special clothing should be provided, fitting well at the neck, wrists, and overlapping at the buttons; the caps should fit close. All clothing should be regularly washed, and never damp when put on. No overalls should be allowed in the eating place; they should be always removed before entering, and donned again before going into the working sheds. Separate dressing and dining rooms should be provided, suitably arranged with washing appliances.
Medical inspection of the works should be made regularly, preferably at the end of the week. The difference in the appearance of the employés at the beginning and end of the week is very noticeable. The number of visits should be not less than once a fortnight. In hot and damp muggy weather, where there is extra pressure of work and longer hours, and in the more dangerous processes, medical inspection should be more frequent.
The inspection should include the sanitary condition of each house, ventilation, number of hours worked, composition of the compound, condition of each employé, sufficiency of washing and drying requisites, the overalls, gloves, respirators, escape of vapour from melting pots or flues, dustiness of the air, cleanliness of the houses, and freedom of tables, floors, etc., from the powder. The surgeon should warn the management of any peculiarly dangerous process, suggest the number of hours to be worked, and notify any workman whom he thinks unfit for it. He may find it necessary to advise an earlier hour to begin work, on account of the heat, and more frequent exchange of workers in the different departments of the manufactory. In selecting men for work, he should choose men of middle age and strong constitution, and, other things being equal, the less frequently new hands are taken on the better. Young women, or nursing mothers, should not be allowed to work, or handle the crude dinitro, the organic compound, or the finished explosive. Pregnancy or anæmia should entail dismissal. The medical officer should watch carefully new beginners at the work, and initiate proper precautions to prevent chronic cases becoming acute. A written notice of employés off work supposed to be due to the effects of the poison should be sent to the medical officer in charge, so that he may investigate the conditions and causes. All employés should be examined and passed by the medical man, and their condition noted before being taken on. He may find it necessary to prescribe short shifts; this may mean either a short continuous number of hours at the work, as in the filling houses; or frequent intermission of work, as can be obtained by the mixing house workers. Sometimes it is necessary to advise very limited spells of work. The process of grinding and cleaning out of flues are operations attended with serious risk. About six hours’ work in the mixing and filling houses daily is as much as an average man can undertake. Headache, sickness, nausea, and distaste for food in the morning should be looked upon as warning symptoms, and men so affected should not be allowed to persist at the work. Heavy muscular exertion is not desirable for those who suffer from anæmia, or the cyanosis caused by the poison.
Alcohol is contra-indicated, and all oils and fats are solvents of dinitrobenzine. Lemons, apples, acid fruits and drinks, and milk, are usually advised; the two latter may be ordered by the medical man with advantage.
Treatment.--There is no known antidote. Symptoms must be combated as they arise. If the poison has been taken into the stomach it must be immediately removed by the stomach tube. Oxygen freely inhaled and saline infusion are necessary. Artificial warmth, diffusible stimulants, and perfect rest must be persisted in until all danger from syncope is past. Warm, easily-assimilated liquid food per mouth and rectum must be given. Later the anæmia requires general tonics, fresh air, and good food.
ROBERT PROSSER WHITE.
XXXIII. DRY CLEANING BY MEANS OF BENZINE
The cleaning of gloves and stained garments by means of benzine is an occupation which gives employment to large numbers of people. In some dry-cleaning establishments naphtha alone is used, so that what has already been said of naphtha in connection with indiarubber trades will equally apply here. The soiled articles are first washed with naphtha and soap in an out-building in which no naked lights are allowed, and then put into a revolving cylinder filled with naphtha. When benzine is the cleansing agent, two kinds are made use of: (1) a petroleum spirit obtained from mineral oil, and (2) spirit obtained from coal tar. In several dry-cleaning establishments fires have suddenly, and often in a most mysterious and unexplained manner, broken out. They have been attributed to friction, electric sparks, and to accidental ignition of the spirit by lucifer matches concealed in the clothes. One of the first things attended to on the arrival of garments to be cleaned is a thorough turning inside out of all the pockets, and the removal particularly of any matches that may have been left therein, also a stripping-off of all metallic buttons from coats, jackets, etc. The workmen are not allowed to smoke nor to have in their pockets any lucifer matches. The work is carried on in outbuildings, one side of which is quite open, so that the freest ventilation possible is obtained. No naked, nor artificial, light of any kind is allowed in these buildings. The garments, after having been examined on their arrival, and sorted, are placed in a revolving drum that contains benzine, and which can be hermetically closed, or in a fixed machine within which there is a revolving cylinder that contains the spirit. By either of these methods the clothes are brought into the closest contact with the benzine. After the garments have thus been sufficiently agitated and cleaned by contact with the benzine, they are removed and placed in a machine known as a hydro-extractor, whereby the excess of spirit is removed. This liquid is allowed to settle, the supernatant clean spirit is decanted off and redistilled. The garments on being removed from the hydro-extractor are rinsed in clean spirit, put through the hydro-extractor again, removed, dried, and finished.
The risks incurred by the workpeople are twofold: (1) danger from fire and explosions; (2) effects of inhalation of the benzine. Fires, as already mentioned, occur in dry-cleaning establishments under the most mysterious circumstances. In one establishment that I visited eight fires and explosions had occurred in fifteen years. In the summer evenings when the weather is sultry, and perhaps several hours after the employés have left off working, fires have broken out in these establishments. The cause of the fire is often unexplainable. It is believed that benzine has a tendency to undergo spontaneous combustion, and that this can be prevented by the addition of a small quantity of oil soap, ¹⁄₁₀ to ¹⁄₁₀₀ per cent., to the benzine, and well mixed with it. This soap is prepared according to the patent of an Austrian firm, Messrs L. Schutte, Landsberg, & Co., by dissolving one kilo of caustic potass, or soda, in four kilos of alcohol. To a litre of this solution one and three-quarter litres of oleic acid are added and the mixture heated. In order to keep the salt in solution there should be added to every 100 parts of the mixture, either before or after heating it, 250 parts of carbon tetrachloride, benzol, benzine, or other suitable solvent. Experience has shown that too great care cannot be taken in regard to the manipulation and storage of benzine. Materials that have just been removed from or cleaned with benzine should on no account be brought near a fire or naked light. Care has to be exercised, too, that naphtha and benzine are not poured into the drains in considerable quantity, for they give off explosive vapours which are dangerous when workmen enter the large drains in a city with naked lights.
Inhalation of the vapours of benzine affect people differently. Some persons are more susceptible than others, and are obliged to retire from the work while others can remain at it. Its effects are more noticeable in young women than men. Females on the whole are more readily intoxicated, they become excited and hysterical. The power of walking is not interfered with. Both men and women complain of headache and giddiness after working in an atmosphere laden with benzine vapour. Occasionally they vomit. Although women seem to be more susceptible than men, yet even the men become intoxicated and feel as if they were drunk. On a sultry afternoon the effects are more pronounced. The workpeople are often obliged to leave the rooms and go out into the fresh air. The vapour of benzine produces in some people a heavy, sleepy feeling, with a sense of great tiredness, amounting to a loss of muscular power and followed by a temporary defect of memory. Naphtha produces similar symptoms. As its vapour is heavier than atmospheric air, the workmen suffer most in hot, close weather.
Prevention.--The air of the workroom should be kept as pure as possible by means of artificial ventilation. In the place where gloves are cleaned the air should be renewed by the running of a fan. No food should be allowed to be taken into the workroom. Attached to each revolving cylinder in which the garments are agitated along with benzine there ought to be an automatic fire-extinguisher. There should be plenty of loose sand lying about to put out any accidental fire, and there ought to be blankets in readiness to throw round any one whose clothes have caught fire. Woollen outer garments should be worn by the workpeople. If a dry-cleaning establishment is a few storeys high, there ought to be fire-escape ladders provided.
Workpeople who have become excited or intoxicated by the benzine should be taken into the fresh air. It is by the respiratory organs that the spirit which has been taken into the blood leaves the system. Anæmic girls who are subject to headache should give up the work, for experience shows that the inhalation of benzine aggravates headache.
THOMAS OLIVER.
XXXIV. USE OF INFLAMMABLE OR SPIRIT PAINTS
Inflammable paints have only come into use within the last twenty years. Known in the trade as quickly drying, composite or spirit paints, they are principally used for painting the interior of ships that put into dock and which the owners can only allow to stay there for two or three days. By their use a ship can be painted and turned out of dock according to the number of men put on to do the work in from one to three days. To the owners of modern steam-ships time is money, and consequently there has grown up of late a considerable demand for these paints. It is in the drying of the ordinary oil-paint that there occurs delay not only in regard to the laying on of a second coating, but in the utilisation of the painted spaces afterwards. With these quickly drying paints it is quite otherwise. Mr James H. Edwards, formerly of Messrs Edwards, ship repairers, South Shields, informs me that in half-an-hour or thereabouts after the first coating of spirit paint has been put on another layer can be applied. They are used more in the painting of old than of new boats. Instead of being ground with oil, the colours are mixed with methylated or petroleum spirit, or with benzine. The paints may contain lead, but there is less danger from the lead than from the spirit. It is the spirit which confers upon these paints their quickly drying properties, but at the same time it renders them extremely dangerous to the workmen alike from inhalation of the vapour and its inflammability. In investigating this question along with my colleagues of the Dangerous Trades Committee of the Home Office, our attention was specially drawn to the fact that as these paints are generally employed for coating spaces in ships that are confined and often dark, men have worked therein with naked lights, and, as a consequence, explosions and fires have occurred. Too often the workman is alone in the confined space, and as he may be rendered unconscious not only by the spirituous vapours rising from the paint, but, in the event of fire, by the products of combustion, he is quite unable to extricate himself from his perilous position. I have seen one man with burns nearly over the whole of his body who had been rescued with difficulty from the bunker in which he was working. It is not only in the confined spaces in the interior of ships that fires suddenly break out, they are not unknown during the painting of the outside of a ship in a dry dock. Momentarily and without any explanation, unless it be that the wind has fanned a naked light or blown a spark, the side of a ship may be enveloped in flame which is just as suddenly extinguished.
It is during the painting of the bunkers, fore and aft peaks, tunnels, ballast tanks, and the holds of ships that the greatest risk is incurred, and especially in the former, since only one man as a rule can work in these confined spaces at a time. Men have been known, after working in one of these confined spaces, to have become excited as if intoxicated, and on being removed to the open air they have vomited. The ejected contents of the stomach have smelt strongly of the spirit paint they were using. For a short period the men have seemed dazed and stupid, and would have fallen if unsupported.
Sometimes exposure of an hour or less to the vapours given off by the paint in a contracted chamber is sufficient to induce unpleasant symptoms. Men have become unconscious in the bunkers and have had to be extricated. On being placed on deck in the open air they have looked pale rather than cyanosed. In some instances where the symptoms have been less severe, there have been difficulty of breathing and a sense of suffocation in the chest, but as a rule these are absent. There is often complaint of a swimming in the head and a feeling of great uncertainty and want of self-confidence, while in other instances the individual falls soundly asleep. Now and again, when the men have been removed from the bunkers bleeding has occurred at the nose. As a rule the intoxicating and stupefying effects of these spirit paints soon pass off on exposing the workman to the open air.
In some of the men I observed a well-marked blue line on the gums, showing that in addition to the danger caused by inhaling spirituous vapours their system at the same time had been exposed to the risk of lead poisoning.
Prevention.--Since these spirit compositions cannot be used to paint the inside of peaks, bunkers, and tunnels of ships, without running considerable risk to the workmen, clearly their employment ought to be prohibited in confined spaces. It is courting disaster to paint the inside of any cramped space, ingress to or egress from which can only take place through a man-hole. No naked lights should be allowed in these places. Illumination should be secured either by a safety lamp or by the electric light. All the workmen whom I have interrogated are unanimously of opinion that the work should be periodically interrupted. Every hour or two, according to the more or less confined character of the chamber in which the paints are being used, the workmen should go into the open air for several minutes. Six hours’ work a day should be the maximum, and this ought to be divided into equal halves, separated at least by one and a half hour’s interval. Since there is considerable risk from fire and explosion, no young or inexperienced person should be allowed to use these paints, and under all circumstances men on being employed for the first time should be informed of the dangers and of the risks they are running. Where a workman is painting the inside of a confined space in a ship with spirit paint he should be frequently visited by a foreman, to see that all is well.
When an individual has become intoxicated through the vapours given off by composite paints, the best treatment is to take him into the open air, and to wrap him up in rugs so as to avoid the chance of his being chilled. When the workman has sufficiently recovered, he should be accompanied home by some of his mates, put to bed, kept warm, and a saline aperient administered at the earliest opportunity.
THOMAS OLIVER.
XXXV. ACETYLENE AND ITS DANGERS
All details relating to the manufacture of coal-gas, water-gas, or oil-gas, and to the incidental risks both to the worker and the consumer, are well known, having been treated by many reliable authorities. Acetylene gas, however, is a comparatively modern illuminant, growing in public favour, and now that the manufacture of calcium carbide is not confined to the United States, Canada, and the Continent, but is produced also in the United Kingdom, it is probable that the adoption of acetylene will become more general.
For country houses, country churches, railway stations, isolated factories and workshops, Indian bungalows, and other places where a cheap and ready supply of coal-gas or electricity is not available, acetylene will be particularly appreciated. Its uses, however, are more extended. On the Continent many towns are lighted with this gas. The Town Commissioners have expressed satisfaction with it as an illuminant for the town of Boyle. For photographic purposes, carriage lamps, magic lanterns, bicycle lamps, etc., acetylene is largely used.
A brief description of the manufacture will be interesting. The writer, owing to the fact that there are as yet few carbide of calcium manufactories in the United Kingdom, can speak with only a limited experience, but he is indebted for information to the Read-Holliday Acetylene Company, to an article which appeared in the Public Health Journal for 29th September 1900, to one on “Electrical Furnaces” recently published in the Windsor Magazine, and to other sources.
The introduction of electrical furnaces capable of producing intense heat has rendered it possible to melt and join together such infusible elements as lime and carbon. When the furnaces are cool, the compound formed is known as “calcium carbide.” If dropped in water it decomposes; some authorities say, almost with an explosion. If simply damped, the decomposition is slower, the product given off being the gas known as “acetylene,”--a colourless gas, stated to contain by weight 24 parts of carbon and 2 parts of hydrogen. In England the electrical furnaces are practically arc lamps on a large scale, the bottom of the furnace being a large carbon block electrically connected to the positive pole of the generator, whilst the upper carbon is connected to the negative. By a simple arrangement the negative pole can be raised or lowered at will, to strike the arc or regulate the intensity of the furnace. A mixture of lime and coke, in the form of fine powder, is thrown into the furnaces for fusion, and when cool it is taken away in lumps ready for use.
Seeing that this industry is one of very modern date, it is of interest to consider whether acetylene gas, during the process of manufacture or in use, is likely to produce injury to health or life. This question may be considered under the following heads:--
(a) The inhalation of dust during the crushing processes and in feeding the furnaces.
(b) The fumes evolved from the furnaces.
(c) The danger of electric shock to the workers.
(d) Explosion during the stages of manufacture.
(e) Explosion, or risk of inhalation of gas, when in use.
During the operation of grinding carbon and lime, and when feeding the furnaces, more or less fine dust must of necessity arise, unless this is prevented by mechanical appliances of a somewhat expensive kind. Some of this dust will be held in suspension by the atmosphere and inhaled by the workers, but as the work is done in practically open sheds, and as the industry is of comparatively recent origin, it is impossible at present to say whether injury to health is caused. Labourers engaged in quarrying limestone are said to be healthy men. The late Dr Arlidge, when referring to workmen employed about lime-kilns, stated that there are grounds for believing that the carbonic acid of respiration is capable of acting upon lime-dust and ridding the lungs of it.
(b) Fumes must of necessity be given off from the furnaces, but mechanical ventilating fans render these harmless.
(c) Little fear of electric shock need be apprehended in this country, the voltage being low, although the current is strong--a result attained by the aid of several brushes and heavy copper strips for conveying the current to the carbons forming the furnaces. An interesting article recently published in the Windsor Magazine describes a visit to Niagara Falls, where the largest furnaces in the world are operated, and where, amongst other industries, is found the manufacture of calcium carbide. Furnaces on the arc and incandescent principle are employed. The current enters the building at a voltage of 2200, to be transformed to about 100 volts, which approximates the pressure found in English works.
(d) An accident of a serious (but happily a non-fatal) nature recently occurred at works in which the calcium carbide, when cool, is stored in 8 cwt. metal tanks, ready to be sent away. It appears that some moisture had found its way into a returned tank. This was unobserved by a worker, who placed about 4 cwts. of the material into it, screwed the lid down, and left the works for the night. The tank stood about 15 feet from the electric furnace. A mechanical fan for ventilating purposes was running, and caused a current from the direction of the tanks to the furnace. As a natural result, gas was generated in the tank during the night. The workman, before resuming work in the morning, took off the lid, liberating the gas, which was at once ignited by the furnace, causing explosion, and seriously injuring the man. The obvious lesson is, that tanks should be carefully examined for moisture or leakage before filling, and that under no circumstances should the filling be done near the furnaces, but in another room, in which there are no lights and no probability of “sparking” from any electrical machine.
(e) On the first adoption of acetylene, accidents happened, giving rise to a general belief that it was dangerous. The following extracts from Orders in Council issued at various times will show that the Government officials were fully alive to this danger, and that from time to time precautions to safeguard the public have been taken. By an Order in Council dated 26th February 1897, certain parts of the Petroleum Acts, 1871–1881, were made to apply to carbide of calcium, and it was laid down that:--
“The label on the vessel containing the carbide of calcium shall bear in conspicuous characters the words ‘Carbide of Calcium,’ ‘Dangerous if not kept dry,’ and with the following caution: ‘The contents of this package are liable if brought into contact with moisture to give off a highly inflammable gas,’ and with the addition:--
“(a) In the case of a vessel kept, of the name and address of the consignee or owner.
“(b) In the case of a vessel sent or conveyed, of the name and address of the sender.
“(c) In the case of a vessel sold or exposed for sale, of the name and address of the vendor.”
On the 7th July 1897, an Order in Council amended the Order of 26th February 1897, by prescribing that:--
“Notwithstanding anything to the contrary in the said Order, the quantity of carbide of calcium which may be kept without a licence shall be as follows:--
“(a) Where it is kept in separate substantial hermetically closed metal vessels containing not more than 1 lb. each 5 lbs. “(b) Where it is kept otherwise None.”
By a further Order in Council, dated 26th November 1897, it was laid down that:--
“Acetylene when liquid, or when subject to a pressure above that of the atmosphere, capable of supporting a column of water exceeding one hundred inches in height, and whether or not in admixture with other substances, shall be deemed to be an explosive within the meaning of the Explosives Act of 1875, subject to the following exception; that if it be shown to the satisfaction of the Secretary of State that acetylene, declared to be explosive by this Order when in admixture with any substance, or in any form or condition, is not possessed of explosive properties, the Secretary of State may, by Order, exempt such acetylene from being deemed to be an explosive.”
The Order further prescribed that:--
“Whereas by section 43 of the Explosives Act, 1875, it is provided that Her Majesty, from time to time by Order in Council, may prohibit, either absolutely, or except in pursuance of a licence of the Secretary of State under the said Act, or may subject to conditions or restrictions, the manufacture, keeping, importation from any place out of the United Kingdom, conveyance, and sale, or any of them, of any explosive which is of so dangerous a character, that in the judgment of Her Majesty it is expedient for the public safety to make such Order.
“And whereas it is in the judgment of Her Majesty expedient for the public safety that acetylene, when an explosive within the meaning of this Order, shall be prohibited.
“Now, therefore, in pursuance of the above-mentioned provision of this Act, Her Majesty is pleased, by and with the advice of Her Privy Council, to order and prescribe that acetylene, declared to be an explosive by this Order, shall be prohibited from being manufactured, imported, conveyed, or sold.”
An Order of the Secretary of State, dated 28th March 1898, provided as follows:--
“Acetylene in admixture with oil-gas in a proportion not exceeding twenty parts by volume of acetylene in every one hundred parts of the mixture, when subjected to a pressure not exceeding one hundred and fifty pounds to the square inch, shall not be deemed to be an explosive within the meaning of the Explosives Act, 1875.
“Provided that the acetylene and oil-gas shall be mixed together in a chamber or vessel before the gases are subjected to compression.”
Lastly, an Order of 15th May 1900 required:--
“That acetylene in admixture with air or oxygen, declared to be an explosive by this Order, shall be prohibited from being manufactured, imported, conveyed, or sold.
“Provided that nothing in this Order shall apply to acetylene in admixture with air when such admixture takes place only in a burner or contrivance in which the mixture is intended to be burnt.
“Provided also that nothing in this Order shall be held to apply to an admixture of acetylene and air which may unavoidably occur in the first use or re-charging of an apparatus, properly designed and constructed with a view to the production of pure acetylene.”
A Committee of the Society of Arts, London, was appointed to investigate the subject and frame rules for the safe construction of acetylene apparatus, and it is claimed (justly I believe) by manufacturers such as the Read-Holliday Acetylene Company, Lockerby and Wilson Limited, and others, that their apparatus fulfils the conditions laid down by the Committee, and that now their appliances may be used with perfect safety. Messrs Tinker & Holliday, of Huddersfield, who manufacture carbide of calcium, give their assurance that they have sold more than 1000 machines, mostly of a large size, some of 600 lights, and that there has never yet been an accident of any kind. On the other hand, it must be remembered that, as acetylene is more explosive than coal-gas, exceptional care should be taken as to where generators are placed, and to avoid the use of lights where leakage is suspected. Early last November a representative of an acetylene firm visited an hotel in a country town in Derbyshire to inspect the generator. The newspapers state that immediately after striking a match a loud explosion occurred, in consequence of which his face and hand were injured.
The Chemical Trade Journal for 16th June 1900 contains a paragraph of public interest, relating to the safety of calcium carbide, which may perhaps with advantage be here reproduced:
“The large army of insurance agents and adjusters who are now in Ottawa settling the losses incurred through the recent fire have lately had before them an object lesson which should remove any doubts that may have been entertained as to the safety of storing carbide of calcium. According to a communication we have received from Mr Andrew Holland of the Board of Trade, Ottawa, when the fire reached the furnace-room of the Dominion Carbide Works, everything in it that would burn was consumed. Three pigs of carbide, however, in three crucibles remained in perfect condition as evidence that they did not explode. The grinding and mixing department and warehouse were in another building, and every effort was made to prevent the fire from reaching it; but the very strong wind blowing, and the vast rush of flame, enveloped all the buildings in the vicinity, and they were in a few minutes reduced to ruins. In the carbide warehouses there were 15 tons of carbide, packed in rolled steel cans with screw covers. When the floor burned, the carbide dropped through into the cellar, in which a foot of water had collected from the firemen’s hose. Here was an ideal combination for an explosion, if carbide is an explosive. Several cans were broken in the fall, owing to the intense heat having opened the seams, and the carbide was dumped into the water. Gas was generated in immense quantities, but it simply burned with a low steady flame, making less show than two cartloads of coke on fire in the immediate vicinity. Had the cellar been dry, the carbide could have been all saved after the fire; but it continued to soak up the water and make gas for some days, and the burning gas kept the carbide so hot, that it could not be handled. As it was, about a ton of it was shovelled out and packed in new cans. Two of the cans were dug out whole from the hot mass, and saved with the carbide, though they were burned like old, worn-out stove-pipes. The insurance agents admit that they have had a practical demonstration which had convinced them how much the ‘risks’ of calcium carbide have been over-estimated.”
It is claimed by the manufacturers of acetylene that it possesses certain hygienic advantages over other gases, these being--a less consumption of oxygen, a less addition of carbonic acid to the atmosphere, less heating of the air, and freedom from sulphur compounds. The illumination is stated to be brilliant, but not injurious to the eyes. On this point, however, it does not appear that oculists in this country have pronounced definite opinions, although individual medical practitioners have reported favourably. Dr W. A. M’Keown, in his Treatise on Unripe Cataract, in a chapter on “Suitable Light and Optical Aids,” says: “Fortunately, however, it is now within the power of the surgeon to whom the electric light is not available to have acetylene light, an illuminant at least as good as the electric light, and very well borne by the eyes.”
An article by Professor Thomas Oliver, published in the British Medical Journal of 23rd April 1898, and entitled “Acetylene, the New Illuminant, and the Dangers arising from its Inhalation,” is probably the only authoritative statement yet published dealing with the physiological effects of acetylene gas. In a brief paper such as this, many details describing the methods of experiment adopted by Dr Oliver must be omitted, but the following is an attempt to summarise the conclusions arrived at by him:--
A mixture of air and acetylene commences to be explosive when it contains 5 per cent. of acetylene (Captain Thomson, H.M. Chief Inspector of Explosives, thinks 3 per cent.), whereas it requires the presence of 8 per cent. of coal-gas to make a similar mixture explosive. It is therefore more explosive than coal-gas. Acetylene has an excessively pungent and disagreeable odour, but this, although a disadvantage in some ways, acts as a warning to individuals of its presence. Generators for private mansions, etc., should be placed in the open air, or in a covered shed open at the sides. In the case of coal-gas and water-gas, death supervenes by asphyxia, owing to the carbon-monoxide entering into extremely stable combinations with the hæmoglobin of the blood. If a rabbit is placed in a bell-jar into which ordinary air and acetylene are pumped, the animal for a long period experiences little inconvenience. If atmospheric air is excluded, and acetylene only admitted, symptoms gradually and slowly develop. After more lengthened exposure to acetylene than that which is necessary for coal-gas, the animal becomes intoxicated, stupor stealing over it, apparently painlessly. When somnolence has been induced and asphyxia not pushed too far, the rabbit, if placed in atmospheric air, shortly afterwards moves about in as lively a manner as if it had not been interfered with. Should the inhalation, however, have been pushed further, and the animal be deeply narcotised, death may ensue. In the minor stages of asphyxia, vascular tension is maintained, but in the deeper stages the vessels are so deeply contracted, that it is almost impossible to obtain a drop of blood. On spectroscopic examination, the blood of a rabbit at different stages of intoxication from acetylene always exhibits the well-marked bands of oxyhæmoglobin, but, unlike the blood in coal-gas poisoning, it is capable of undergoing reduction. In this respect it behaves like ordinary blood. If asphyxia caused by acetylene is not too profound--and under ordinary domestic circumstances it would not be a pure acetylene atmosphere that would be inhaled by an individual, but one mixed with a large proportion of common air--the danger to life seems to be less than it would be in coal-gas poisoning, and the prospect of recovery by removal to atmospheric air greater. Death may supervene, however, if the inhalation has been lengthened, and atmospheric air excluded. In the treatment of unconsciousness caused by the inhalation of acetylene gas, it is necessary to remove the individual into the open air, and to try artificial respiration.
Since this brief article was framed, a handbook for the student and manufacturer has been published by Professor Vivian Lewis, dealing in an exhaustive form with everything relating to acetylene. It is illustrated profusely, and doubtless will become a standard book of reference.
In November 1900, the Foreign Office published a Consular Report by Dr Frederick Rose, H.M. Consul at Stuttgart, on “The Rise, Progress, and Present Condition of the Carbide and Acetylene Industries in Germany,” containing statistics and detailed information of considerable value, but which cannot well be here reproduced. It is shown that thirty towns or villages in Germany, with populations varying from 6000 to 382, are lighted by acetylene. In Berlin the Imperial Post Office has made a beginning by lighting two of its branch post offices with this gas, and has installed an apparatus with sixty jets in the head post office. In July 1898, 62,000 jets of acetylene were installed in Germany. In the first months of 1899 the number had increased to 170,000. Reference is made to a new application of calcium carbide in the production of pure metals from their ores by its use as a reducing agent; to the manufacture of lampblack, it being stated that acetylene gives three to four times as much lampblack as good oil-gas; and to an invention which utilises carbide for the production of converted steel, as well as for hardening armour-plate after Harvey’s process.
On 1st December 1900, The Public Health Engineer devoted the whole of its issue to acetylene, and as the article gives in detail descriptions of generators and other appliances made by practically all recognised firms, together with a statement of what is claimed in regard to safety and economy in use, it may be helpful to mention this publication, for the benefit of inquirers.
HAMILTON P. SMITH.
XXXVI. FLOUR MILLS
Flour-milling as conducted in this country a few decades ago was, despite the fact that most of the mills were situated in the country, an unhealthy industry. Flour millers died from pulmonary consumption and chest diseases in a larger proportion than men engaged in other trades in the same district. The average life of a miller was said to be forty-three years. Hirt compiled tables of the comparative sickness of millers and bakers, and he showed that while of one hundred bakers seven died from pulmonary phthisis, out of the same number of millers the deaths were ten. Bakers and millers seemed to him to be about equally predisposed to emphysema of the lungs, but as regards pneumonia the mortality figure for bakers was 8.4 per cent. as against 42 per cent. for millers. These statistics are taken from a German source, and it is difficult to explain the very heavy mortality rate from pneumonia in millers compared with that of bakers.
Until within thirty years ago all the wheat and oats in this country were ground between revolving stones. During the grinding a considerable amount of fine dust was given off, the continual inhalation of which was held responsible for much of the ill-health of the operatives. So unhealthy was the occupation of milling believed to be twenty years ago, that Friendly Societies would not accept operative millers as members. To-day no objection is raised. In addition to injury to health from breathing the dust-laden atmosphere, there was a risk from fire owing to the highly explosive character of the dust. While danger to life from explosions in flour mills still to some extent prevails, both it and the risk to health from inhalation of the dust have materially diminished. There is the widest divergence possible between the old and the new methods of milling. The introduction of the steam roller system of milling from Buda-Pesth, and the fact that nearly all the various processes are carried on inside closed machinery, have cleared the atmosphere of modern flour mills and converted what was admittedly a dangerous trade into one that compares very favourably with most occupations. Wherever the old method of milling is still carried on the atmosphere is found laden with a very fine dust, mostly flour. This with each inspiration is drawn into the bronchial tubes of the miller, and forms plugs with the mucus secreted by these passages. The plugs, owing to their tenacity, are dislodged with difficulty. It is not contended that the flour itself reaches the lungs; probably the whole, or at any rate the most of it, becomes entangled in the mucus of the smallest bronchial tubes, but in the dust there are other things than flour present, e.g., portions of the husks of harder grain than wheat, portions of hairs of oats, bristles of rye, and particles of mineral from the grinding stones (see Microphotographs, page 276), so that through one thing and another, and in consequence of the repeated bronchial irritation and the cough caused by respiring the dust-laden air, a strain is imposed upon the lungs that leads to over-distension of the air cells, or what is known as pulmonary emphysema. That portions of bristle, etc., are capable of being inhaled into the deeper recesses of the respiratory passages is shown by the presence of these bristles on microscopical examination of the expectoration that has been discharged after hard coughing.
As a nation we are dependent upon foreign countries for our food supplies, especially wheat. Some of the wheat that is imported is extremely dirty, particularly that from the River Plate, India, and Persia. It not only contains small stones and sand, and the husks of other seeds, but often particles of soil that have been contaminated by manure. In going over a large modern flour mill one is struck by the amount of dirt that is taken out of wheat. It is therefore necessary to clean the grain, which is done by first removing all solid impurities and then washing it. To clean it, the wheat is passed through a separator composed of sieves that are kept vibrating. By this means the larger impure particles are removed, while by the operation of a strong current of air the lighter dust is sucked away. After this preliminary cleaning the wheat is taken to rotatory sieves, which size the grain and thereby separate the larger from the smaller seeds. It is now ready to be washed. This is done by allowing the wheat to fall into a tank of warm water, through which a stream is constantly running. From this it is removed to dryers and coolers. It is only the very dirty wheat that is washed. Some of it is simply scoured and brushed inside a conical iron cylinder by means of beaters or brushes that are revolving rapidly. The dust given off escapes through fine slot holes.
In modern flour mills the dangers that operatives are exposed to are: (1) those incidental to the machinery; (2) fire and explosions; and (3) inhalation of dust. It is with the latter that we are here most concerned. The cleaning of wheat is a dusty process, but it is usually carried on within enclosed machinery, and so long as this and all the covered-in spaces are provided with fans that are kept in good order, and the pipes leading away from these to the dust chambers are kept patent, the workmen do not seem to incur any great risk to health. Attention, however, must be given to keeping the suction-pipes clean and the fans in good order, otherwise, as cleaning is a very dirty process, the men would assuredly suffer in their chest. At several of the large flour mills where Oriental wheat is ground, and to the grains of which particles of manure are often adherent, I have on several occasions interrogated the men as to whether any illness had ever followed the washing of the foreign wheat, but in no instance could I learn of any illness being traceable to such a source. Once the wheat has been cleaned and brushed or washed, it is put through the rollers and is milled into flour. This consists of not one but many processes, all of which are conducted in enclosed chambers, the product at each particular stage being lifted and carried onwards by self-regulating machinery and elevators from one part of the mill to another. Where the fittings of the machinery are good, no dust practically escapes. Hence it is that flour-milling has ceased to be the harmful industry it formerly was. In filling the sacks with flour, and in cleaning returned sacks, there is often a considerable amount of dust given off, but mechanical contrivances are now in operation that greatly minimise the amount of dust, so that this particular operation too has become less dangerous than it once was.
THOMAS OLIVER.
XXXVII. MINING
The industry of mining, touching as it does the boundaries of nearly every field of human activity, necessarily presents itself under so many and such different aspects, that the complete study of the risks to life, limb, and health to which those engaged in it are exposed, involves an unusually large number of diversified considerations. It is here proposed to examine only the risks that are more directly incidental to mining proper, and these again only in so far as they affect the miners themselves, leaving out of consideration entirely the dangers to which mining operations may expose the population in whose midst they have to be carried on, although these are far from unimportant, including, for example, such accidents as a fall down an unfenced shaft, the destruction caused by the explosion of a dynamite magazine, the possibility of being struck by a stone projected by a blast, the injurious effects of fumes arising from smouldering waste heaps, or from the calcination of pyritic ores, and extending in extreme cases to the collapse of entire districts, as, for instance, in the salt-mining area of Cheshire.[109]
The entire subject of mining is generally looked upon as divisible into three main branches, namely, “prospecting,” or the search for mineral deposits; “mining” properly so called, or the exploitation of these deposits; and “dressing,” or the preparation for the market of the minerals produced.
Of these three branches the risks incidental to the last named are practically those to which workers in any ordinary factory are exposed, and need not be further considered here; whilst minor accidents, such as cuts and bruises, are common enough, especially when mineral is broken by hand, serious casualties, on the other hand, are fortunately rare. The only precautions needed are those indicated in all cases where men, and in the case of dressing works, often boys, girls, and women also are at work in the midst of machinery in motion. It may just be mentioned that, in certain branches of gold mining, a solution of cyanide of potassium is used as a solvent for extracting the gold; this solution is not only extremely poisonous when taken internally, but also produces in many instances painful sores on the hands and arms of the men working with it.
The life of the prospector is necessarily a most arduous one, and for which men of exceptionally good physique and sound health are alone suitable. The typical prospector starts off, generally by himself, sometimes with a mate, to examine an unknown and at times uninhabited district; or worse still, the inhabitants may be uncivilised races, hostile to the white man, and thus their presence only introduces another and a serious danger to the prospector. At the best he can only carry a limited amount of food with him, and has often to depend on his gun for a great part of his supplies. He has, therefore, to time his journeys accurately, so as to enable him to get back to civilisation before his stock of provisions or ammunition is exhausted, and many a poor fellow has paid with his life for the rash eagerness that has led him too far afield in his search for valuable minerals. In some countries, such as Western Australia, not only has food to be arranged for, but drink also, great areas being absolutely without potable water; there is no doubt that many an explorer in this great auriferous continent has perished of thirst[110] in his search for the precious metal.
When mining operations have to be undertaken by the prospector, these usually take the form of sinking small shafts, less rarely of driving levels. In either case the timbering is of the crudest character, any branch of a tree, piece of bamboo, or similar weak support being generally looked upon as sufficient. The windlass is usually a rough concern, made entirely, or almost entirely, of wood, and the writer was once a witness of the remarkably narrow escape of a prospector who was being hoisted up a shaft by a couple of natives with the aid of such a rudimentary windlass, after having lit a couple of shots in the shaft bottom, when one of the rough wooden handles of the windlass suddenly broke. To the risks incidental to working with imperfect appliances must be added those due to the fact that only native labour, always utterly inexperienced in mining and often unused to work of any kind, is available, whilst the prospector has to undertake, single-handed, the task of both instruction and supervision.
It but rarely happens that the prospector is fortunate enough to find a healthy climate at the scene of his operations, although such is the case in some parts of Australia, South Africa, etc. As the greater portion of the temperate zone habitable by civilised man has been pretty well ransacked for minerals, the prospector is generally compelled to resort to tropical regions for his hunting ground, and is, therefore, often subject to all the risks of an unhealthy climate, amongst which malarial fever in its various forms is perhaps the most formidable. Prospecting in Central America, the northern half of South America, West Africa, and Central Africa, parts of India, Siam, Burma, the Malay Archipelago and Peninsula, and some parts of Australia means in each case the strong probability, amounting almost to a certainty, of being attacked by malaria, which, though not necessarily fatal, only too often undermines the strongest constitution. Finally, it must be remembered that whenever a rich “strike” has been made and a rush sets in to any small area, the townships that spring up thus suddenly are invariably unhealthy at first, even in the healthiest climates. “What is everybody’s business is nobody’s business,” and the most elementary rules of sanitation are disregarded with the most frightful recklessness, until the number of victims becomes so serious as to compel attention. In this way Kimberley, Johannesburg, Coolgardie, Menzies, etc., have all been visited by epidemics of typhoid or enteric fever.
That the Polar regions are no more favourable to the prospector than are the Tropics is only too clearly shown by the death-roll of those who have been seeking their fortunes of recent years in the Yukon and other similar parts of far North-Western America. Statistics of the mortality of prospectors, whether by disease or by accident, are, of course, not available in any form, but no one who has had much to do with prospecting can fail to recognise that there are few more dangerous, just as there are few more fascinating, occupations.
Turning next to mining proper, as carried on in civilised countries, it becomes necessary to investigate separately the accidents and the diseases incidental to the miners’ calling. Careful statistics of mining accidents are kept by many countries, notably Germany, France, Belgium, and Great Britain, and a comparison of these statistics would, no doubt, enable us to deduce results of the highest importance if these statistics were at all comparable. Unfortunately, however, the definitions of what constitutes a mining accident on the one hand, and of what constitutes a fatal mining accident on the other, are either extremely vague, or else will be found to differ in each country. In Great Britain we have no legal definition at all. The Coal Mines Regulations Act, section 35, merely says that “loss of life” or “serious personal injury” due to an accident must be reported, unless the accident be due to “any explosion of gas, or of any explosive, or of any steam-boiler,” when every personal injury whatever, whether serious or not, has to be reported. The Act, construed literally, seems to require only the reporting of any accident that is instantly fatal, or of a serious accident that terminates fatally under the head of “Loss of Life.” If a trivial accident, such as would not need reporting under the Act, happens to end fatally, as, e.g., when a slight cut or scratch causes blood-poisoning and ultimately death, the Act seems to deliberately exclude such accidents from the list of fatalities. In the absence of clear legal guidance, most inspectors seem to include in their list of fatal accidents all accidents of any kind whatever that terminate fatally within a year and a day from the date of the occurrence of the accident. This may not be law, but it is certainly common sense. The term “serious personal injury” is interpreted very differently in different places, the ultimate decision resting with the colliery manager and the colliery doctor. Thus one doctor may hold that a simple fracture is not a “serious” accident, and need not be reported; whilst another may consider a bad cut or bruise, perhaps not sufficient even to lay a man off for a day, as a “serious” accident, though the majority rather incline to the view that no accident is “serious” unless there is rather more than a possibility that it will end fatally. This wide discrepancy of opinion makes it very difficult to compare fairly the accident statistics of different parts of the Kingdom, and, as the sequel will show, the British official non-fatal accident statistics are practically worthless.
In Germany each state or kingdom has its own mining law. The Prussian law, which is the most important by far of any, and which all the others follow more or less closely, merely says, that any accident that has caused death or serious injury to one or more persons must be at once reported. The accident statistics based upon these reports are, therefore, even less satisfactory than our own; it would appear as though the law contemplated only the inclusion of cases of instantaneous death in the list of fatal accidents, whilst non-fatal accidents are quite undefined. The Prussian official statistics record only fatal accidents in mines, except in the case of explosions of fire-damp, when injuries are also recorded. Fortunately, however, accurate statistics have been kept for some time past of all mining accidents by the Official Miners’ Permanent Relief Fund of the German Empire. This assurance association defines a fatal accident as one that causes death, whether instantaneously or after any length of time. Non-fatal accidents are divided into such as incapacitate the injured person from working for either a longer or a shorter period, the limit between these two classes being fixed at thirteen weeks. A distinction is also made between accidents that permanently, and those that temporarily, disable a miner, and again between those that cause total, and those that cause partial, disablement. As this Insurance Fund of Germany is under the direct supervision of the Governmental authorities, the statistics published by it have all the character of official documents.
In France mining accidents are simply divided into those that cause injuries merely and those that cause death, there being apparently no precise definitions of either.
In Belgium a mining accident is one that has for its consequences the death or severe injury of one or more persons--severe injury being defined as an injury of such a nature as to cause the ultimate death or to interfere with the regular work of the victim. Apparently the Belgian law, strictly interpreted, would include amongst the fatal accidents only those where the injured person is killed on the spot, but in the published statistics, a fatal accident is understood to be one that causes death within thirty days of its occurrence. Obviously this definition is much narrower than that used in Great Britain, a fact that must not be lost sight of when statistics of the two countries are compared.
Perhaps the most exhaustive analysis of mining accidents is to be found in a work published in 1897 by the above-mentioned Official Miners’ Permanent Relief Fund of the German Empire,[111] which covers the period from 1st October 1885 up to 1st January 1895. This Relief Fund, administered under Government supervision, deals with all accidents that incapacitate the victims from work for a longer period than thirteen weeks, all accidents of lesser importance, here called minor accidents, being dealt with by a separate fund worked in conjunction with the former. The total number of persons insured for one year during the period covered by this work was 3,623,175; the total number of accidents of all kinds notified was 278,371, distributed as follows:--
Per 1000 Persons Numbers. Employed.
Fatal accidents 7,721 2.13 Accidents causing total permanent disablement 1,427 0.39 Accidents causing partial permanent disablement 14,367 3.97 Accidents causing temporary disablement 8,164 2.25 ---- 8.74 Minor accidents 246,692 68.09 ------- ----- Total 273,371 76.83 ======= =====
Although, as will be seen subsequently, the ratio of fatal accidents is slowly but steadily decreasing in all the more important mining countries, the ratios between the various classes of accident appear to remain approximately constant. It is, however, notorious that ever since the laws providing compensation for accidents have received their present form, the number of non-fatal accidents reported in Germany has been steadily increasing year by year, there being no satisfactory explanation that can be assigned for this fact. The serious accidents are classified in various ways, the most interesting of which are those that refer to the causes of the accidents. Thus, of the above serious accidents, it is shown that the distribution was as follows amongst the various branches of mining:--
+--------------------------+---------+-----------------+-----------------+ | | | Fatal Accidents.| Serious | | | | | Accidents. | | | No. of +-------+---------+-------+---------+ | | Persons | |Per 1000 | |Per 1000 | | |Employed.|Number.| Persons |Number.| Persons | | | | |Employed.| |Employed.| +--------------------------+---------+-------+---------+-------+---------+ |(a) Coal Mines |2,378,673| 6020 | 2.53 |19,130 | 8.04 | |(b) Lignite Mines | 331,522| 617 | 1.86 | 1,354 | 4.08 | |(c) Metalliferous Mines | | | | | | | and Smelting Works | 58,853| 870 | 1.14 | 2,750 | 3.62 | |(d) Salt Mines and Brine| | | | | | | Works | 95,423| 143 | 1.50 | 450 | 4.71 | |(e) Other forms of | | | | | | | Mining | 58,704| 71 | 1.21 | 274 | 4.66 | +--------------------------+---------+-------+---------+-------+---------+
It is interesting to note that the ratio of accidents above ground to those below was as follows in the various branches of mining:--
Below Ground. Above Ground.
(a) Coal Mines 84.7 per cent. 15.3 per cent. (b) Lignite Mines 45.1 „ 54.9 „ (c) Metalliferous Mines and Smelting Works 73.5 „ 26.5 „ (d) Salt Mines and Brine Works 51.4 „ 48.6 „ (e) Other forms of Mining 42.3 „ 57.7 „
The information is unfortunately not complete, as the relative numbers of the workers above and below ground are not given, so that no idea can be formed from these data of the relative degree of risk of work above and below ground.
As regards the time at which accidents occur, there are a few more in the forenoon than in the afternoon, as might well be expected, seeing that the average number of men at work is greater in the former than in the latter period. As regards the days of the week, the percentage of accidents occurring on the respective days is as follows:--
Sunday 2.2 per cent. Monday 15.1 „ Tuesday 16.2 „ Wednesday 16.6 „ Thursday 15.9 „ Friday 16.7 „ Saturday 17.0 „
Excluding, of course, Sunday, it is noteworthy that the number of accidents in the second half of the week is notably greater than in the first half; apparently the only cause that can be suggested for this circumstance is that the men, being more fatigued towards the latter end of the week, are on that account more liable to accidents. It may well be, however, that the facts here noted are themselves merely accidental, and that observations extended over a larger period would tend to equalise the numbers.
Two highly interesting series of tables give an objective and a subjective division of the causes of the accidents, showing in what manner and by whose fault these originated. The former table may be summarised as follows:--
KEY:
A: Falls of Rock, Coal, Falling Bodies, etc.
B: Transport, Haulage, Winding, Loading, etc.
C: Falls from Ladders, Steps, or other Heights.
D: Explosions.
E: Machinery in Motion, Motors, etc.
F: Molten Metal, Hot and Corrosive Liquids, Poisonous Gases.
G: Miscellaneous. +-----------------------------+--------------------------------+ | | Causes of Accident per cent. | | Branch of Mining. +----+----+----+----+---+---+----+ | | A | B | C | D | E | F | G | +-----------------------------+----+----+----+----+---+---+----+ |(a) Coal Mines |41.1|26.2| 9.1| 9.2|5.7|1.0| 7.7| |(b) Lignite Mines |35.9|28.7|14.8| 3.5|7.9|3.4| 5.8| |(c) Metalliferous Mines and| | | | | | | | | Smelting Works |34.4|20.8|13.1|10.2|5.6|1.9|14.0| |(d) Salt Mines and Brine | | | | | | | | | Works |13.7|31.5|23.6| 7.9|7.3|7.6| 8.4| |(e) Other forms of Mining |31.9|25.2|12.2| 9.6|2.9|...|18.2| |All Mines |39.4|25.8|10.2| 9.0|5.9|1.3| 8.5| +-----------------------------+----+----+----+----+---+---+----+
The accidents due to these various causes calculated per 1000 people employed in the whole mining industry were as follows:--
Falls of Rock, Coal, Falling Bodies, etc. 3.44 Transport, Haulage, Winding, Loading, etc. 2.26 Falls from Ladders, Steps, or other Heights 0.89 Explosions 0.78 Machinery in Motion, Motors, etc. 0.51 Molten Metal, Hot and Corrosive Fluids, Poisonous Gases 0.12 Miscellaneous 0.74 ---- Total (Fatal and Serious Accidents) 8.74 ====
There were no less than 3.42 accidents per 1000 workers due to falls of rock and coal in the workings, whilst those due to explosions of fire-damp were only 0.31 per mil. It will be seen in the sequel that accidents due to falls of ground of various kinds play by far the most important part in mining casualties everywhere.
In distributing the blame for these accidents, four main groups are distinguished, accidents being either apparently unavoidable and therefore put down to the intrinsic danger of the occupation, or else due to some fault of omission or commission either of the mine owners or managers, of the victims themselves or of their fellow-workers. The numbers for the entire mining industry are given as follows:--
Per cent. Inherent danger of the occupation 58.2 Per cent. Defects in or absence of safety appliances 0.2 Insufficient regulations 0.1 Other faults of management 0.9 Faults of the mine owners --- 1.2 Neglect of fellow-workers to use safety appliances 0.1 Contravention of regulations by fellow-workers 1.1 Unskilfulness of fellow-workers 0.3 Carelessness of fellow-workers 2.4 Ignorance of danger on the part of fellow-workers 0.1 Gross negligence of fellow-workers 0.5 Faults of fellow-workers --- 4.5 Neglect of victims to use safety appliances 0.9 Contravention of regulations by victims 6.4 Unskilfulness of victims 4.8 Carelessness of victims 20.3 Ignorance of danger on the part of victims 2.0 Gross negligence of victims 1.5 Fault of victims --- 35.9 Unknown causes 0.2 ----- 100.0 =====
This table shows, in the first place, that 41.6 per cent. or two-fifths of all the accidents could have been avoided by proper care and intelligent thought on the part of all concerned; and in the second place, that fully one-third of the accidents can be ascribed to the faults of the victims themselves. This means that whilst the occupation is not necessarily much more than half as hazardous as the accident statistics make it appear, there is but little room for improvement either in the appliances used or in the regulations framed for the safety of the miners, and that the remedy lies largely within their own grasp, the better education of the miner and the development of his thinking powers being the best protection that can be offered him against accident. This view is further supported by the fact that in coal-mining the unavoidable accidents are as high as 61.7 per cent., whilst the avoidable accidents fall to 28.2 per cent. (0.1 per cent. being ascribed to unknown causes). It may be taken as fairly well known that the coal miners are amongst the better educated and the more highly trained of all classes of miners, the effect of their higher intelligence being indicated in these figures.
It is interesting to compare the above data with the results given in a recent paper by Mr B. M’Laren on “Preventible Colliery Fatalities,”[112] in which that gentleman analyses the fatal accidents in Great Britain during the years 1896–98, and points out that 35 per cent. of the total number of underground fatal accidents were preventible. In coming to this conclusion, he has included “all fatalities stated to have been brought about by carelessness or neglect; those in which a deficiency of props, sprags, bars, chocks, packs, etc., are mentioned; cases of want of judgment; a moment’s forgetfulness on the part of some one; acts contrary to the Coal Mines Regulation Act, special rules, and ordinary regulations; want of care, etc.; and those which present themselves as possibly preventible; while all apparently doubtful cases are omitted.” It may be added that this writer, like most others on this subject, concurs in the view that “the best preventive for colliery accidents is technical education.”[113]
These German figures have been dealt with at considerable length because they give the most complete picture anywhere obtainable of the liability of miners to serious or fatal accidents. Although the tables in the work dealt with extend only up to the year 1895, they are still perfectly applicable to the present day; this is perhaps best seen by taking the proportion of fatal accidents for the decade 1890 to 1899, when it will be seen that though these fluctuate considerably about the average for the period under consideration, yet their general average agrees pretty well with that of the period covered by the work quoted, namely, 1885 to 1895:--
Death-rate Year. per 1000 Persons. 1890 2.19 1891 2.44 1892 2.05 1893 2.27 1894 1.91 1895 2.16 1896 2.21 1897 2.05 1898 2.53 1899 2.03 ---- Average 2.18 ====
No other equally complete data are available for any other country. In addition to the special report that has been here summarised, this official Relief Fund publishes annual statistics,[114] and these can be compared with the official statistics published annually by the Government from the returns collected by the Inspectors of Mines; it is true that these latter do not refer to the German Empire as a whole, but are published separately for the principal mining states, namely Prussia[115] and Saxony[116]; the Prussian statistics are especially useful, because, out of the total number of miners employed in the German Empire, no less than nine-tenths are included in the kingdom of Prussia.
* * * * *
The following table shows the proportion of Fatal Accidents as given in the above quoted Prussian statistics for 1899:--
+-------+---------------------------------------------------+ | | Fatal Accidents per 1000 Persons Employed in | | +-----------+-------+-------------+--------+--------+ | Year. |Bituminous |Lignite|Metalliferous| Other | All | | |Coal Mines.| Mines.| Mines. | Mines. | Mines. | +-------+-----------+-------+-------------+--------+--------+ | 1891 | 2.889 | 1.825 | 1.035 | 1.018 | 2.395 | | 1892 | 2.208 | 1.710 | 1.081 | 2.224 | 1.963 | | 1893 | 2.619 | 2.089 | 0.794 | 2.298 | 2.245 | | 1894 | 2.209 | 1.986 | 1.005 | 1.935 | 1.983 | | 1895 | 2.540 | 2.103 | 1.002 | 1.917 | 2.229 | | 1896 | 2.577 | 1.664 | 1.137 | 1.649 | 2.241 | | 1897 | 2.353 | 2.362 | 1.046 | 1.611 | 2.124 | | 1898 | 2.864 | 1.992 | 0.994 | 1.956 | 2.485 | | 1899 | 2.314 | 1.945 | 1.393 | 1.231 | 2.114 | |Decade | | | | | | |1890–99| 2.518 | 1.946 | 1.079 | 1.708 | 2.204 | +-------+-----------+-------+-------------+--------+--------+
These figures refer to the total number of workers both below and above ground; an analysis for the year 1899 gives the following results:--
Per 1000 Persons Employed Underground. Fatal accidents due to explosions 0.079 „ „ haulage and winding 0.874 „ „ falls of coal and stone 1.191 „ „ after-damp 0.112 „ „ blasting 0.121 „ „ miscellaneous causes 0.142 ----- Total fatal accidents underground 2.519 ===== Per 1000 Persons Employed Above Ground. Total fatal accidents above ground 1.082
Per 1000 Persons Employed in Open Workings. Total fatal accidents in open workings 1.455
It will be seen that the death-rate per 1000 persons employed is very nearly the same as that given by the Relief Fund Association, an agreement that goes far to confirm the belief above expressed in the general reliability of these statistics. It is important to note that metal-mining is in Germany a far safer occupation than coal-mining, a state of affairs that would naturally be expected to obtain, having regard to the conditions of safety of these two classes of work, and bearing in mind that in Germany the educational level of both classes of miners is more nearly the same, and that the legislation for both is practically identical. It should be added that the above statistics refer only to persons regularly employed in mines, and excludes fatal accidents that may occur in or about any mine, to persons not comprised in the category of regular mine employés; the inclusion of such cases would increase the above total figure by about 2.5 per cent.
In Belgium, careful statistics of accidents are published,[117] and in spite of the fact that her coal mines present circumstances of special difficulty, the recorded death-rate is a low one, due partly to the fact already pointed out, that only deaths within thirty days of the accident are reported. Moreover, in Belgium, deaths due indirectly to mine accidents are excluded from the lists. Coal-mining being the chief mineral industry of Belgium, the mineral statistics of that kingdom are more particularly devoted to it. The death-rate has been as follows in the Belgian coal mines from the year 1895 to 1899:--
+-------+---------------------------------------+ | | Death-rate per 1000 Persons Employed. | | Year. +-----------------+---------------------+ | | At Surface and | Underground only. | | | Underground. | | +-------+-----------------+---------------------+ | 1895 | 1.33 | 1.58 | | 1896 | 1.14 | 1.38 | | 1897 | 1.03 | 1.31 | | 1898 | 1.40 | 1.71 | | 1899 | 0.97 | 1.09 | +-------+-----------------+---------------------+
In 1899 there were 241 separate accidents underground, causing 101 deaths, and 151 serious injuries; of these, 85 accidents, killing 48 and injuring 43 workmen, were due to falls of rock or coal; accidents due to haulage produced 63 casualties, of which 19 were fatal, the majority, or 39 accidents, occurring in roads which were approximately level. There was only one explosion of fire-damp, causing 4 deaths, but there are 6 fatal accidents recorded as due to choke-damp. An interesting table shows that the number of accidents due to falls of rock or coal has produced an annual average of 0.73 deaths per 1000 men employed, the year 1899 happening to be considerably below the average in this particular category.
In France also, great attention is paid to conditions affecting the security of the miner. Great care is exercised by the Inspectors of Mines, and the accident death-rate appears to be decreasing steadily and satisfactorily, but, in comparing the French statistics with these of other countries, it must be remembered that the former include only accidents that result fatally within a few days of their occurrence, there being no rule at all on the subject. The following table shows the death-rates per thousand since 1894[118]:--
+-----+--------------------------------------------------------------------+ | | Death-rate per 1000 Persons Employed. | | +--------------------------------------------------------------------+ | | In Coal Mines. | In other Mines. | In all Mines. | |Year.+-------+-------+------+-------+-------+------+-------+-------+------+ | |Under- | Above | |Under- | Above | |Under- | Above | | | |ground.|ground.|Total.|ground.|ground.|Total.|ground.|ground.|Total.| +-----+-------+-------+------+-------+-------+------+-------+-------+------+ |1894 | 0.97 | 0.55 | 0.85 | 0.92 | 0.54 | 0.81 | 0.96 | 0.55 | 0.84 | |1895 | 1.41 | 0.68 | 1.19 | 1.73 | 0.31 | 1.32 | 1.43 | 0.65 | 1.20 | |1896 | 1.62 | 0.50 | 1.30 | 1.97 | 0.90 | 1.67 | 1.65 | 0.53 | 1.33 | |1897 | 1.34 | 0.41 | 1.07 | 2.52 | 0.84 | 2.06 | 1.44 | 0.44 | 1.10 | |1898 | 1.26 | 0.60 | 1.07 | 3.06 | 2.00 | 2.75 | 1.41 | 0.72 | 1.21 | |1899 | 1.62 | 0.66 | 1.29 | 2.11 | 1.02 | 1.78 | 1.67 | 0.70 | 1.39 | +-----+-------+-------+------+-------+-------+------+-------+-------+------+
Coal-mining forms the principal portion of the French mining industry, over 90 per cent. of those engaged in mining being employed in collieries of various kinds. Metal-mining is comparatively unimportant, and is generally carried on upon a small scale, a fact that in part no doubt accounts for the relatively high accident death-rate. In coal-mining, on the other hand, the rate is a very low one. Many French collieries are controlled by large corporations, and in these large and well-managed concerns all work is done with the greatest care, and carried on in the most approved style.
Italy is rarely looked upon as a mining country, yet there are over 60,000 persons annually engaged in mining proper in the kingdom of Italy, the mining being practically all metalliferous mining. The following are the recent Italian accident statistics[119]:--
+-----+--------------------------------------------------+ | | Per 1000 Persons Employed. | | +----------------+----------------+----------------+ |Year.| Underground. | Above ground. | Total. | | +-------+--------+-------+--------+-------+--------+ | |Killed.|Injured.|Killed.|Injured.|Killed.|Injured.| +-----+-------+--------+-------+--------+-------+--------+ |1897 | 2.77 | 3.23 | 0.78 | 0.86 | 2.31 | 2.67 | |1898 | 1.75 | 3.50 | 0.46 | 1.39 | 1.41 | 2.95 | |1899 | 2.10 | 3.29 | 0.42 | 1.08 | 1.66 | 2.72 | +-----+-------+--------+-------+--------+-------+--------+
It is worth noting that about two-thirds of the fatal and one-half of the non-fatal accidents underground are due to falls of stone, this being here, as elsewhere, the most prolific cause of disaster. The comparatively high death-rate in Italy cannot well be due to any of the conditions of mining, none of the mines being particularly deep, or presenting any conditions of abnormal danger or difficulty. It is more than probable that the high rate is due to the low educational level of the Italian miner. Whilst not less naturally intelligent or skilful than his fellow-worker in Britain, Germany, or France, his technical training is far inferior, and to this deficiency the higher accident death-rate in Italy may fairly be ascribed.
In the United States it is only within quite recent years that any attempt has been made to obtain accurate statistics of mining accidents, and these are still mainly confined to coal mines; even now the inspection of these leaves a good deal to be desired. The following figures are given for miners other than coal miners in an article by F. L. Hoffman,[120] from which most of the following information is derived:--
+------------------------------------------------+-------------------+ | |Accident Death-rate| | Occupation, Locality, and Year. | per 1000 | | | Persons Employed. | +------------------------------------------------+-------------------+ |Iron Ore Miners, Michigan (1892–96) | 5.14 | | „ „ (1899–1900) | 3.62 | |Copper Mines, Lake Superior (1892–96) | 3.57 | | „ „ (1898–99) | 2.07 | |Metal Miners, Colorado (1896–97) | 3.89 | |Metal Miners (Lead and Zinc), Missouri (1892–97)| 2.59 | +------------------------------------------------+-------------------+
It is obvious that the collection of accurate statistics in the Western States, where the mines are much scattered and there is practically no inspection, is quite out of the question.
The following table, taken from the paper above quoted, shows the accident death-rate in coal mines in the various States of the Union during the period 1886–1897, as far as such statistics are available:--
States and Accident Death-rate Territories. per 1000 Persons Employed. Alabama 1.63 Colorado 4.72 Illinois 1.82 Indiana 2.32 Indian Territory 3.76 Iowa 2.28 Kansas 1.62 Kentucky 1.50 Maryland 1.63 Missouri 2.19 New Mexico 9.42 Ohio 1.53 Pennsylvania (Anthracite) 3.15 Pennsylvania (Bituminous) 1.88 Tennessee 4.16 Washington 10.70 West Virginia 3.30
In all bituminous coal mines (average) 2.12 In all anthracite mines (average) 3.15 In all coal mines (average) 2.53
The first point that is brought out by this table is that anthracite mining is evidently more dangerous than bituminous coal-mining, and this is the more striking seeing that anthracite coal does not give off fire-damp, so that the dangers of gas explosions are here excluded. The general conditions of anthracite mining, and more particularly the steep inclination and great thickness of many of the seams, are sources of danger that are not met with in ordinary coal-mining. Although, as has been already pointed out, comparisons between the statistics of different countries must be made with the utmost caution, it seems certain that the accident death-rate in the bituminous mines of the United States is higher than in the more important European coal-producing countries. There seems to be nothing in the nature of the bituminous coal mines of America to account for this fact, which is no doubt largely due to the circumstance that the American coalfields do not as yet possess a settled coal-mining population properly so called, and that experienced coal miners are therefore rare, any working man taking casually to coal-mining for a while, as he might to any other temporary occupation. Such men can of course never gain the experience and almost intuitive knowledge of coal-mining that is acquired by coal miners in the older continent, who are generally born and bred on the coalfields and imbibe knowledge about coal-mining matters from their earliest childhood. Another equally potent factor is the extraordinary mixture of nationalities to be found in most American coal mines, which seem to be the first refuge for the immigrant labourer from Eastern or South Eastern Europe. The result, of course, is that regulations or orders are only half understood, and are therefore not properly obeyed. Attention has recently been directed to this source of danger in various parts of the world; for example, the employment underground of persons who are not acquainted with the German language has recently been forbidden in the Westphalian coalfield. It is worth while noting that the States in which machine coal-cutting is most largely employed, such as Ohio and Illinois, show death-rates well below the average of the United States as a whole.
Turning now to Great Britain, there is a large mass of statistical material available by which the liability to accident of the British miner may be gauged. Each of H.M. Inspectors of Mines in charge of a district issues an annual report, a great portion of which is devoted to mining accidents and their causes, and these district reports are summarised in the General Report and Statistics, Part II., Labour, whilst an advance proof is also published early in each year. It may be as well to point out first of all that the death-rate due to accidents has been steadily diminishing during the last half century,[121] as is well shown by the following table, worked out for quinquennial periods from 1851 to 1899:--
+------------+------------------------------------------------------------+ | | Average Annual Death-rate per 1000 Persons | | | Employed in all Mines in Great Britain. | | +--------------------------------------------+-------+-------+ |Quinquennial| | Above | | | Period. | Underground. |ground.| Total.| | +-----------+--------+-------+-------+-------+-------+-------+ | | Due to | Due to | In | Misc- |Due to |Due to |Due to | | |Explosions.|falls of|Shafts.| ellan-| all | all | all | | | | Ground.| | eous. |Causes.|Causes.|Causes.| +------------+-----------+--------+-------+-------+-------+-------+-------+ | 1851–1855 | 1.280 | 2.016 | 1.296 | 0.556 | 5.149 | 1.012 | 4.301 | | 1856–1860 | 1.234 | 1.846 | 0.899 | 0.648 | 4.628 | 0.994 | 3.883 | | 1861–1865 | 0.618 | 1.714 | 0.668 | 0.790 | 3.791 | 1.105 | 3.240 | | 1866–1870 | 1.158 | 1.578 | 0.528 | 0.730 | 3.995 | 1.256 | 3.433 | | 1871–1875 | 0.516 | 1.210 | 0.437 | 0.572 | 2.736 | 0.899 | 2.342 | | 1876–1880 | 0.811 | 1.132 | 0.317 | 0.449 | 2.709 | 0.847 | 2.306 | | 1881–1885 | 0.408 | 1.108 | 0.263 | 0.532 | 2.312 | 0.848 | 2.007 | | 1886–1890 | 0.312 | 1.015 | 0.196 | 0.517 | 2.042 | 0.913 | 1.806 | | 1891–1895 | 0.244 | 0.798 | 0.188 | 0.470 | 1.704 | 0.820 | 1.524 | | 1896–1899 | 0.117 | 0.783 | 0.122 | 0.457 | 1.479 | 0.798 | 1.338 | +------------+-----------+--------+-------+-------+-------+-------+-------+
This table shows that as far as comparisons with other countries are at all possible, mining in Great Britain has reached a level of safety with which but few other nations can compare favourably; it also brings out the very satisfactory fact that the accident death-rate is steadily decreasing, although further investigation will show that all branches of the mining industry do not share equally in the decrease. Great Britain is essentially a coal-mining country, its metal-mining having been for years constantly diminishing until it is now almost a negligible quantity; it must, however, be remarked that by one of those curious legislative freaks that are so familiar to the miner in this country, the only remaining important branch of metal-mining, namely, ironstone-mining, is for legal purposes included under the head of coal-mining, and figures as such in all these statistics. About 95 or 96 per cent. of all persons employed in mining work in the coal mines as thus legally defined, over 93 per cent. being employed in coal-mining properly so called. The following table shows the death-rates for quinquennial periods from 1875 to the end of 1899 for coal and metal miners, taken separately, using these words in their official sense:--
+------------+-----------------------------------------------+ | | Average Annual Death-rate in Great Britain | | | per 1000 Persons Employed. | | +-----------------------+-----------------------+ |Quinquennial| | | | Periods. | In Coal Mines. | In Metal Mines. | | +-------+-------+-------+-------+-------+-------+ | |Under- | Above | Total.|Under- | Above | Total.| | |ground.|ground.| |ground.|ground.| | +------------+-------+-------+-------+-------+-------+-------+ | 1876–1880 | 2.752 | 0.936 | 2.396 | 2.170 | 0.432 | 1.472 | | 1881–1885 | 2.310 | 0.962 | 2.046 | 2.338 | 0.461 | 1.600 | | 1886–1890 | 2.038 | 0.970 | 1.834 | 2.116 | 0.318 | 1.428 | | 1891–1895 | 1.686 | 0.874 | 1.526 | 2.250 | 0.392 | 1.482 | | 1896–1899 | 1.462 | 0.816 | 1.340 | 1.898 | 0.468 | 1.305 | +------------+-------+-------+-------+-------+-------+-------+
An examination of this table shows very clearly that practically all the improvement has been confined to coal-mining. Leaving surface labour out of question for the moment, it is seen that the death-rate amongst coal miners for the period 1896–99 is little more than half of what it was in 1876–80, whilst in metal-mining there has only been a somewhat doubtful improvement of about 12½ per cent. Contrary to the popular opinion, coal-mining in this country is obviously now a very much safer employment than metal-mining, and has been so for about the last twenty years. The death-rates of surface workers have in both cases remained about stationary during the last twenty-five years. It is evidently nearly double as high at collieries as it is at metal mines, the reason for this being undoubtedly the greater complexity of surface machinery, the far more intensive rate of work at the former, and above all the fact that the surface works of the vast majority of collieries are connected by a network of railway lines and sidings. That these are a grave source of danger needs hardly any proof, but such is easily obtainable, seeing that the accident death-rate of all males in Great Britain is about 0.87[122] per 1000, whilst that of railway employés, such as pointsmen, porters, guards, etc., is no less than 2.286[122] per 1000. It is evident that the higher death-rate at the surface of collieries as compared with metalliferous mines is easily enough accounted for, and the fact is, moreover, indicated in the statistics themselves. For example, in 1899, nearly 60 per cent. of the total number of surface accidents at collieries were returned as due to this cause. The suggestion of a remedy is unfortunately a far more difficult matter; this necessarily lies largely in the hands of the men themselves, and whilst it must be admitted that working about and amongst railway trucks is a dangerous occupation, it is a danger that can be considerably lessened by the care and attention of the workers themselves.
An analysis of the causes of fatalities in coal mines leads to several important conclusions. In the first place it is obvious that the danger which is most prominently connected in the public mind with coal mines, that, namely, of explosions, is now one of the least formidable.
The death-rate from explosions within the last five years has been as follows in all the collieries of the United Kingdom:--
Death-rate Year. per 1000 Persons due to Explosions. 1895 0.10 1896 0.31 1897 0.03 1898 0.05 1899 0.09
These figures have now become so small that they are necessarily irregular, an accident of any magnitude, causing even a dozen deaths, being sufficient to affect the rate very greatly. The improvement within the last twenty years is extremely marked, and is due to various causes, among which may be enumerated better ventilation, the far more extended use of safety lamps, the substitution in all dangerous mines of safer explosives for the once universally used black powder, and above all, of some better method of firing for the highly dangerous “squib.” It is highly probable that further improvements may be looked for with every prospect of success in this latter direction, and that the general adoption of electric firing would be a distinctly valuable safeguard. The recognition of the fact that coal-dust is an explosive agent but little less dangerous than fire-damp, due largely to the labours of Professor W. Galloway and Mr H. Hall, and the precautions in the form of watering now adopted, have also played an important part in reducing the death-rate. It need hardly be added that most of these precautions would have been of little value, even if their introduction had been possible, unless the scientific training of managers, officials, and men alike had concurrently made considerable advances. It is scarcely possible to enforce in a coal mine laws or regulations of which the more intelligent, at any rate, amongst the miners themselves do not see the use, and legislation alone could do but little, unless there existed a general feeling in the mining community that it was tending in the right direction. It needs a certain amount of technical and scientific training, however, to enable the average coal miner to realise such a fact, and that he has been brought to realise it is one of the main factors in the increased security that men enjoy nowadays.
The main cause of disaster underground has always been, and still remains, that classed as “falls of ground,” to which considerably over half of the deaths underground are due. Explosions have now been so far brought under control that an explosion has come to be looked upon as an abnormal accident, due to a fault of omission or commission on the part of somebody, and therefore requiring careful investigation, whilst falls of ground are unfortunately still regarded as normal risks incident to the miner’s calling. These falls may be subdivided according as they are falls at the working face, when they are either falls of roof or falls of the coal face, or they are “backbye” accidents, that is to say, falls of roof in the roadways of the mine. Falls at the face are accountable for over 70 per cent. of the total number of deaths due to falls, but unfortunately our statistics do not discriminate between falls of coal and falls of roof at the face. In the absence of definite information on this important point, it is difficult to suggest what remedies should be applied, but these must depend greatly upon what may be found to be the most fertile causes of accident; falls of the roof, properly speaking, can only be avoided by setting more props, or by setting them better; falls of coal may be due to bad “spragging,” or to the undercut mass of coal falling forward, or to its coming away at one of the natural cleavage joints of the coal. In Germany a Government Commission has been appointed to inquire into the whole question of falls of ground, and no doubt the report, when issued, will throw much light upon this difficult subject. It is obvious that the two kinds of falls require entirely different treatment; systematic timbering, i.e., the setting of props at regular uniform distances apart, whether the roof seems to need it or not, is being advocated in several quarters, and it should certainly do something to reduce the number of accidents due to falls of roof. Falls of coal can hardly be treated in the same way; systematic spragging might do something, but would probably not of itself be sufficient. A very obvious mode of reducing the accident rate at the working face should be found in the more extensive use of coal-cutting machinery; in the first place the number of men necessary to be employed at the coal face for a given output would be very considerably reduced, and hence the number of men exposed to this danger would be proportionally diminished. Furthermore, as the machine cuts rapidly, and must be kept moving constantly if it is to be economically successful, the men working it will always be under a comparatively fresh roof, which is far less liable to sudden falls than a roof that has been laid bare for some time, the same being true also of a freshly-cut face of coal, which should never, under these conditions, be left standing long enough for the weight of the roof to affect it. Finally, a man working with a machine has a far better chance of looking about him and seeing what is going on than has a miner lying on his side, half under the coal, engaged in “kirving his holing,” that is to say, in hewing out with his pick a narrow strip of coal along the floor of the seam, an operation that has to be performed preparatory to breaking down the mass of coal.
It is highly probable that one of the conditions that has contributed very largely to the prevention of colliery explosions, namely, the extended use of safety lamps, has at the same time been a contributary cause of the non-diminution in the number of accidents due to falls of ground. Among the conditions that have been laid down from time to time by Royal Commissions and others as essential to a good safety lamp, that of giving a sufficient amount of light has been very generally overlooked, and most of the safety lamps in use give a very poor light, especially after they have been burning for a few hours. Their shape, moreover, prevents their giving a top light, so that it is scarcely possible for a miner to adequately examine the roof of his working with a safety lamp, so as to see whether it is dangerous or not. Much was hoped from the introduction of portable electric lamps, but so far these have not come up to expectations, partly because no entirely satisfactory electric lamp has yet been devised, partly because the ordinary electric lamp does not, like the ordinary safety lamp, indicate the presence of gas, and thus allows the miner to continue his work without giving him warning that he is in an atmosphere in which he ought not to remain. A really good safety lamp, giving a light all round at least equal to that of an ordinary candle, is a great desideratum at the present moment.
Of the remaining causes of accidents underground, the most serious are those connected with the transport of the coal; the various systems of mechanical or self-acting haulage in use in all collieries of any importance must always give rise to a certain number of accidents, but it can only be said that the number of these could be greatly diminished by a stricter attention to colliery regulations. A large number are due annually to men and lads riding upon the tubs, so as to save themselves the exertion of walking to or from the shaft bottom. Shaft accidents have fortunately diminished considerably within the last twenty years, having come down to about one-third of what they were; much of the improvement is no doubt due to the greater attention now being paid to the quality and condition of the winding ropes. A notable proportion of the accidents classified under this head occurs not in regular mining, but during the sinking of shafts, an operation that always of necessity involves a good deal of risk.
Turning next to metal-mining, the most striking fact is that the conditions of safety have undergone such small improvement; the figures of course fluctuate a good deal from year to year, because the total number of men engaged is so small that a very few accidents more or less affect the ratios very considerably. It should be noted that metalliferous mines, as defined by law, include a large number of mines in which no metallic minerals are wrought, and should more properly be described as all mines not included under coal mines; the metalliferous mines properly so called show a far higher death-rate than is returned for the miscellaneous mines legally described as metalliferous. Here again, as in coal mines, the largest number of casualties is due to falls of ground, by which nearly two-thirds of the total number of deaths is caused. In metal-mining, the miner’s safety must depend far more than in coal-mining upon the worker’s own judgment, experience, and carefulness; it can only be suggested that mine managers should see to it that an ample supply of suitable timber is kept close to all the working places, and that the timbering of all levels, etc., should be constantly inspected by special officials appointed for this purpose.
The most interesting problem that presents itself for solution is, however, the question why the form of mining that was the safer of the two twenty-five years ago in this country, and which is still far the safer in Germany, is now the more dangerous, and why the death-rate in one should have been reduced 50 per cent., whilst in the other it has remained practically stationary. The only salient point of difference to be found between the present regulations affecting the two forms of mining is, that whilst the Coal Mines Regulation Acts insist that no man shall be allowed to act as either manager or under-manager of a colliery unless he has passed certain prescribed examinations, any one is at liberty to manage a metalliferous mine, whether he be qualified to do so or not. The result has been that the educational level of coal miners as a whole has been raised; every intelligent coal miner knows that the only road to ultimate promotion lies through these examinations, and therefore applies himself to the scientific study of his work. There are thus growing up in every coalfield in Great Britain numbers of technically well-educated young men, from whom colliery managers can select their colliery officials, and the higher educational standard thus attained by the officials is slowly but surely affecting both the working miner on the one hand, and the manager on the other, as it is obvious that the latter dare not remain on an intellectually lower plane than his subordinates. It is probable this educational development has played a leading part in the improved conditions of safety in coal mines, not only directly, by increasing the knowledge and thinking powers of the miners, but indirectly, as already said, by rendering legislation easy that would scarcely have been possible without it, all of which merely amounts to another repetition of the statement, that improved education is the best safeguard of the miner against accident. It will be remembered that the same conclusion was already drawn from the comparison of the accident death-rates of various countries, the highest death-rates being found in the most ignorant nations. Although much has been done in this country within the last twenty-five years, very much still remains to be done in order to bring up the educational level of all connected with mining to the high standard of scientific technology that is to be found in some other countries.
It should here be pointed out that mining, and more especially coal-mining, is really not the highly dangerous occupation that it is usually thought to be. The annual average accident death-rate[123] for all males in Great Britain is 0.870 per 1000, with which the present rate for coal miners underground of 1.462 per 1000 does not compare very unfavourably. The true accident risk of the miner is perhaps best seen by comparing it with a few of the other trades that are usually classed as dangerous:--
Average Annual Accident Occupation. Death-rate per 1000 in the years 1891–93.
Bargeman, Lighterman, etc. 3.765 Seaman, Merchant Service 3.219 Dock Labourer, etc. 2.411 Railway Guard, Porter, Pointsman, etc. 2.286 Railway Engine Driver, Stoker 1.340 General Labourer 1.155
As regards non-fatal accidents, it has already been pointed out that the official statistics of this country are of practically no value, owing to the absence of any standard or definition of what constitutes an accident to be reported. The following table shows the number of persons injured in mines (non-fatal accident cases) according to the official statistics:--
+------+------------------------------+ | |Number of Persons Injured per | | | 1000 Persons Employed. | | Year.+--------------+---------------+ | |In Coal Mines.|In Metal Mines.| +------+--------------+---------------+ | 1895 | 7.49 | 6.96 | | 1896 | 8.29 | 9.89 | | 1897 | 6.42 | 8.29 | | 1898 | 5.74 | 9.75 | | 1899 | 5.66 | 10.10 | +------+--------------+---------------+
It will be seen presently that these figures are ludicrously disproportionate to the real casualties, and although it is difficult to get accurate data about these, an approximation, at any rate, to the true facts can be obtained.
Valuable information is afforded by the various Miners’ Permanent Relief Funds, and by the Central Association for dealing with distress caused by mining accidents. The latter Association publishes statistics, from which the following table has been compiled, this representing the summary of the returns from the nine English societies (there are no Scotch or Irish ones) which together compose the Association[124]:--
+------+---------+------------------------------+ | | | No. per 1000 Members. | | | No. of +---------------+--------------+ | Year.| Members.| Of Deaths by |Of Disablement| | | |Fatal Accident.| Cases. | +------+---------+---------------+--------------+ | 1889 | 238,892 | 2.12 | 188.3 | | 1890 | 268,985 | 2.66 | 157.2 | | 1891 | 287,690 | 1.88 | 149.8 | | 1892 | 295,676 | 2.17 | 139.8 | | 1893 | 299,027 | 1.59 | 144.8 | | 1894 | 313,438 | 2.50 | 159.4 | | 1895 | 317,004 | 1.99 | 166.8 | | 1896 | 325,708 | 1.90 | 177.6 | | 1897 | 334,428 | 1.76 | 192.6 | | 1898 | 271,536 | 1.81 | 196.3 | | 1899 | 279,842 | 1.67 | 176.6 | +------+---------+---------------+--------------+
The accident death-rate reported by the Association is rather higher than is shown in the Inspectors’ Official Reports, because in the latter only deaths that occur within a year and a day of the accident are included, whereas in the tables compiled by the Association all deaths that can be referred to mining accidents are given, however long the interval may be between the accident and the death of the injured person.
The disablement cases in the above table comprise all injuries received by any member of the Association that are sufficiently serious to keep the victim off work for at least a week. They are more than twenty times as numerous as those included in the Inspectors of Mines’ Reports, and this may be accepted as conclusive evidence that these reports do not record by any means all cases of “serious personal injury.” It is true that the two sets of statistics are not in all respects strictly comparable; the Inspectors of Mines take no account of an accident unless it happens within the precincts of the mine as legally defined, while the Associations’ regulations extend to accidents that may happen to miners going to or returning from their work. There is also a suspicion that occasional cases of disability to work are returned as due to accident, when they are really not so caused, and escape the vigilance of the various societies’ officials. Making all allowances, however, for these and similar defects, the above figures may be looked upon as reasonably accurate, and as fairly representing the risk of minor accidents to which the coal miner is exposed in this country; it may be added that the figures for each individual society do not vary very greatly from the general average, as shown by the Association. It is difficult to see why they should be about twice as high as the corresponding accidents in Germany, for although there may be some laxity in admitting supposed accidents, this circumstance cannot possibly account for one-half of the cases. It would be a decided advantage if Inspectors of Mines had power to record and report all cases of “smart money” and of compensation respectively paid by the collieries in their districts, as fairly accurate statistics of minor accidents could be obtained in this simple manner. It would also be more satisfactory if all accidents were subject to the examination of special medical officers appointed solely for this purpose. In this way the suspicion would be avoided that a medical practitioner may at times take too lenient a view of a doubtful case, biassed perhaps by the fact that his livelihood may depend largely upon the goodwill of the miners, who often form the bulk of his patients.
By far the most important of the individual societies that make up the Central Association is the Northumberland and Durham Miners’ Permanent Relief Fund; from the annual reports of this society useful information may be gathered, some of which is summarised in the following table:--
+------+---------+-------------------------------------+ | | | No. per 1000 Members. | | Year.| No. of +-------+--------------+--------------+ | | Members.| Of |Of Permanently|Of Temporarily| | | |Killed.| Disabled. | Disabled. | +------+---------+-------+--------------+--------------+ | 1896 | 122,257 | 1.33 | 1.96 | 156.6 | | 1897 | 124,920 | 1.60 | 1.94 | 156.8 | | 1898 | 127,564 | 1.24 | 1.96 | 152.1 | | 1899 | 130,552 | 1.50 | 2.00 | 148.4 | +------+---------+-------+--------------+--------------+
According to the rules of the society an injured man whose injuries prevent him from working for a week is considered as “temporarily disabled,” and he continues in this category until he is fit to return to work, unless he is so badly hurt as to be unable to work for six months, when he is classed as “permanently disabled”; such a man may either recover sufficiently to be able to work again, or he may die, or he may remain disabled for life. The duration of permanent disablement as above defined has of course risen gradually from the commencement of the fund, until it amounted to 5.17 years in the quinquennial period 1887–91, its average duration from the formation of the fund having been 4.42 years.[125]
The duration of temporary disablement was about:--
3.5 weeks in the year 1896 3.6 „ „ 1897 3.55 „ „ 1898 3.55 „ „ 1899
In the Liverpool district, the ratio of permanent disablement is found to be 4.5 per 1000 members, and of temporary disablement 180 per 1000 members; the duration of the former cases averages 3½ years, and that of the latter 4.3 weeks.
Annual reports are also issued by the Prussian Official Miners’ Relief Fund; the report for 1898 gives the accident death-rate of the members of the Association as 2.69 per 1000 members, the death-rate from all other causes being 5.39, making a total death-rate of 7.58 per 1000. It is worth noting that the average age at which members are totally incapacitated from working is 49.2 years, whilst the average age at which members are partially incapacitated is about forty-five years; this includes disablement due to old age as well as to accident.
Coming lastly to the subject of the diseases of miners, it may first of all be stated that mining is a distinctly healthy occupation. The mortality of all males[126] in Great Britain during the years 1890–92 was 18.74 per 1000, out of which 0.87 deaths were due to accident, leaving 17.87 per 1000 due to what may be termed natural causes. On the other hand the mortality among coal miners from all causes for the same period was 12.33, that due to accident being given as 2.00,[127] making the death-rate due to natural causes only 10.35 per 1000. Of course it must not be forgotten that the working miner’s career covers just that period of life at which the natural death-rate is lowest. There are no doubt several circumstances that contribute to the general healthiness of the miner’s occupation; in the first place, mining is hard work, and men whose constitution is not tolerably sound, and whose physique is not fully up to the average, will either select some less arduous occupation at the outset, or will find themselves, if they began life as miners, unable to continue at the work. On the other hand, the work, though arduous, requires steady though only moderate exertion, and does not expose the worker to the abnormally violent strains, exerted through brief periods, that characterise some other occupations. Again, the hygienic conditions are, as far as the coal mine at least is concerned, far more favourable than in most other occupations. The miner works in a good atmosphere, ample ventilation being a prime necessity for ensuring the safety of the coal miner, in an equable temperature, free from the extremes alike of heat and cold, he is not exposed to the inclemencies of the weather, and his working place is usually dry. The same cannot always be said of the miner in metalliferous mines, where the conditions of work are far less favourable in every respect, and his mortality is therefore higher. It may be added that the coal miner, if even moderately industrious, can always earn a wage ample to keep him in fair comfort, and to supply him fully with all the necessaries of life. Probably the most unhealthy part of the coal miner’s work consists in “kirving” or undercutting the coal, in doing which the miner has to lie on his side on the floor of the coal seam, swinging his pick with a peculiar sideways stroke over his head, till he has cut out a narrow groove some 3 feet deep below the over-hanging mass of coal. Work in this constrained position is necessarily harmful to some extent; its effect has been most noticed as affecting the nervous system, and especially the nerves of the eyes, the disease known as miner’s nystagmus having been often ascribed to it. Cases of miner’s nystagmus occur, however, also among miners who do not have to kirve, and it may well be due in great part to the poor light obtainable in so many cases underground, especially when safety lamps are used, and the consequent strain on the eyes; at any rate this seems to be the opinion of several who have suffered from this complaint. The coal miner working in this position is also bound to inhale a considerable amount of fine coal-dust, which has an irritating effect upon the lungs; thus it appears from the tables already referred to that the percentages of deaths of coal miners due to the respective causes indicated were as follows:--
Causes of Death. Percentage of Total Number of Deaths. Accident 16.2 Phthisis 10.7 Bronchitis 12.4 Pneumonia 10.9
The most obvious remedy for reducing the proportion of diseases due to the above causes is the one already referred to, namely, the general use of mechanical coal-cutters, and the replacement of hand kirving by machine kirving. Another cause besides coal-dust that is probably answerable for a considerable proportion of diseases of the lungs is the universal custom among coal miners in this country of walking home in their damp and dirty pit clothing, instead of changing into warm, dry clothes at the mine. Colliery owners have tried the experiment of providing changing houses and baths for the men at the pit’s mouth, but have always found that the men declined to avail themselves of these conveniences.
It has been pointed out that the metal miner’s work is far more unhealthy than that of the collier. This is well seen in the death-rate among Cornish tin miners, the typical metal miners of Great Britain. Here we find that the death-rate, instead of being below the average of the country, is higher, namely 19.66 per 1000 from all causes, that from accident being given as 1.14, leaving 18.52 per 1000 as the death-rate from disease. Consumption is extremely fatal amongst tin miners, bronchitis also claiming many victims. The following table shows the percentage of the total number of deaths for the period 1890–92, due to the causes specified:--
Cause of Death. Percentage of the Total Number of Deaths. Accident 5.8 Phthisis 29.9 Bronchitis 13.5 Pneumonia 5.4 Other diseases of respiratory system 7.1
It is worth noting that according to Dr Ogle’s figures the percentage of deaths in the period 1880–83 amongst Cornish miners (which may be taken as practically equivalent to the tin miners quoted above) due to phthisis was 37.5, and to other diseases of the respiratory organs, 24.9, the death-rate from all causes being rather more than double that of the average of all males. It is probable that a good deal of the improvement that appears to have taken place in those ten years is due to the increasing replacement of ladders by cages for getting the men to and from their work; there seems little doubt that the fatigue of having to climb up a good many hundred feet of steep ladders at the end of a hard day’s work is a prolific cause of chest complaints and of heart disease. At most Cornish mines of any importance a “dry” is provided, i.e., a room or building in which the miners change their wet and dirty mine clothes, and leave them to be properly dried for the day following. As in coal mines, so in metal mines, the dust produced by the miner’s work is apt to injure the men’s lungs. In metal-mining this dust is chiefly produced by the action of drilling. When a drill hole inclines well below the horizontal, water can and always should be poured in, to convert the dust produced into mud, and thus to prevent it from flying about. When a hole “looks upwards” or is pointed above the horizontal, water cannot be poured in, but may be splashed in from time to time; this, however, involves a certain amount of trouble, and is rarely done, although it ought to be. It is especially important in the case of machine drills, which work very much faster and cause much more dust than hand drilling. The compressed air by which these drills are usually actuated can easily be employed to force a small jet of water into the drill hole; this is done by some machines, and is to be highly recommended. Some Continental makers have extended this idea, and use drills pierced longitudinally with a small hole, through which water is injected; this plan seems to be very effective in preventing dust, but may be found open to some other objections in practice.
The fumes produced by blasting, especially when nitro-glycerine explosives are used, are said to be occasionally injurious to health. There is no doubt that the explosion of ordinary black blasting-powder produces a considerable amount of carbonic oxide, and this poisonous gas is also produced, though apparently in less quantity, by most of the so-called safety explosives used in coal-mining. There is, however, never or rarely any good reason why a miner should be exposed to these fumes, which can be cleared away rapidly, provided that the mine is properly ventilated. It has been remarked that in most cases where such ill effects have been complained of, the fault has lain with the men themselves.
It is very exceptional that mining operations, properly so called, necessitate working in air under pressure, though this may occur in some special methods of shaft-sinking or of driving levels through wet ground; it is well known that men working under these conditions are liable to suffer from caisson disease. None but sound, healthy men, not too old, should be employed on such work; they should work short shifts, remain a sufficient time in the intermediate air-lock, and it is advisable that they should be under medical observation or periodic examination as long as the work lasts. In Westphalia the law forbids men working for more than six hours in any place underground the temperature of which exceeds 29° C. (84° F.).
Of special diseases that particularly affect miners, there can hardly be said to be any. On the Continent, particularly in Belgium,[128] and more recently in Australia, especially in North Queensland, a good deal of alarm has been caused by the prevalence of a serious disease due to an intestinal parasite known as Anchylostomum Duodenale. This disease, once introduced, spreads with alarming rapidity; thus in one Hungarian pit, 80 per cent. of the workers were found to be affected, and in pits in the province of Liège from 50 to 69 per cent. were attacked; in Westphalia, in 1897, there were 275 cases of the disease amongst 56,370 miners. The principal, if not the only remedy for this very serious, and often fatal disease, consists in the strictest personal cleanliness on the part of the miners themselves, whilst the management should take care to provide portable sanitary appliances, properly disinfected, at suitable places underground, and an ample supply of clean water for washing purposes. This has been made compulsory by recent legislation for the Westphalian coal mines. At German collieries bathing facilities are always provided, but the same Act now compels the use of separate shower baths in the place of the general plunge bath, the latter having been found to be a means of propagating not only anchylostomiasis, but other contagious diseases, such as trachoma (contagious disease of the eyes), typhus, etc.
There are a few special diseases due to special cases of mining poisonous minerals, which only just need passing mention. It may be said that the only poisonous minerals mined are the ores of copper, arsenic, lead, and mercury. The mining of copper never seems to have given rise to any trouble, and it is even disputed by some authorities, whether copper, taken into the system in small quantities, acts as a poison.[129] Arsenic is usually mined in the form of arsenical pyrites, and does not seem in this shape to have any injurious effects. It is said that dust from the mineral smaltite (an arsenide of cobalt, containing no sulphur when pure), when drawn into the lungs produces cancer of the lungs,[130] and that this disease is not uncommon amongst the miners in the Schneeberg district of Saxony, where the above mineral occurs.
In ordinary lead mines, lead poisoning or plumbism is almost unknown; in the mortality tables already quoted, only one case of death is referred to plumbism among 16,827 miners. This is apparently due mainly to the fact that in all British lead mines the supply of oxidised lead ores is practically exhausted, and work is confined to the sulphuretted ores. Galena, the sulphide of lead, is a heavy and difficultly soluble substance, and it would seem that lead is not readily absorbed from it into the system. The case is far different when the softer oxidised ores of lead, such as the carbonates, are worked, and these have been a source of serious trouble at the mines of the Broken Hill district, New South Wales. It was found that men could not safely be kept at work in those parts of the mine which produced the earthy lead carbonates for more than a fortnight at a time.[131]
Mercurial poisoning is no doubt the most serious of all these special forms of mining disease, due to the fact that all ores of mercury carry more or less mercury in the metallic state, as also to the readiness with which metallic mercury volatilises even at ordinary temperatures. At the Almaden mines in Spain, and the Idria mines in Carniola, a good deal of mercurial poisoning is found to occur; the chief remedy adopted seems to be the working of short shifts, so as to expose the men for as short a time as possible to the dangerous fumes. At the New Almaden mines in California statistics have shown that there were amongst the miners 10.44 per cent. of cases of mercurialism (salivation) in one year (1890).[132] The following remarks on this subject in the report are worth quoting:--
“The miners employed in the extraction of ore work by contract as a rule, and a certain number of careless men, through their own negligence, become victims to mercurial salivation. Men engaged in ore chambers, where native mercury is found, are requested not to eat, drink, or smoke, without first cleaning the face and hands, and using a solution of potassium chlorate as a mouth wash. Working stripped to the waist is discouraged.
“As the greatest attention is paid toward the attainment of perfect ventilation, which is of prime importance in the prevention of mercurial sickness, it is the physician’s belief that if the miners were more thorough in the use of the above precautions, the salivation rate at the mine would be under 1 per cent., whereas it is now over 10 per cent. It is probable that there will always be a slight amount of mercurial sickness, owing, very likely, to the suspension in the moist atmosphere of the mine of a small amount of the chlorides, and possibly other salts of mercury.”
This last example, therefore, serves to repeat and enforce the lesson that seems to be taught by every portion of this investigation, namely, that although mining is from the very nature of the occupation accompanied by certain risks, and although enlightened legislation and careful and scientific management can do much towards diminishing these risks, the main prophylactic must always lie in the thoughtfulness and intelligence of the miners themselves, and that the best thing that can be done towards increasing the safety of mining operations is to raise by all possible means the intellectual status of mining communities.
HENRY LOUIS.
XXXVIII. THE AIR OF MINES
The air of mines of whatever kind is extremely liable to vitiation, the nature and extent of which is of considerable importance in relation to the health and safety of those working in the mine. The impurities met with are known to the miners under such names as “black-damp,” “fire-damp,” “after-damp,” “white-damp,” “gob-stink,” etc.; and these terms will as far as possible be adhered to in the present account of the subject.
In all mines a current of air to all parts is secured by means of the arrangement of the shafts and roads. One shaft, known as the “downcast,” serves for the supply of fresh air, which is distributed by means of “intake” roads to the working places. The more or less vitiated air then passes along a corresponding system of “return” roads or passages to the “upcast” shaft, by which it leaves the mine. In coal mines, where a very large ventilation is necessary, the current is usually maintained by means of a centrifugal fan placed at the top of the upcast, or in some cases by a furnace at the bottom of the upcast. In metalliferous mines the warmth of the mine commonly causes sufficient up-current, without any artificial aid. It is evident that by analysing the return air, and measuring its rate of flow, we can obtain the best idea of the nature and amount of the general vitiation of air throughout the whole mine, while analyses made at particular points in the mine afford more information with regard to vitiation due to special local conditions.
Black-damp.--So far as is known the impurity known to miners as black-damp is met with to a greater or less extent in all, or nearly all, mines, and in many wells. Black-damp is recognised by the fact that when present in small quantities it causes a candle or lamp to burn dimly, without at the same time producing any distinctly noticeable effect on men: that in larger amounts it extinguishes lights; and that in still larger amounts it causes death by suffocation. It is never explosive when present by itself, and is almost always heavier than air, unless, as very frequently occurs in coal mines, it occurs mixed with fire-damp.
Until lately black-damp was believed to issue from coal and other strata, and was commonly identified with carbonic acid. Investigations by Mr W. N. Atkinson and the writer[A] have shown that this belief is erroneous, and that black-damp is nothing else than the residual gas, resulting from the action of air on oxidisable material present in coal and other materials. Pure black-damp, free from air and other gases, consists of a mixture of nitrogen with usually from 5 to 15 per cent. of carbonic acid.
The following table shows the composition of the black-damp obtained from various coal-mines, metalliferous mines, and wells. The samples were usually mixed to a greater or less extent with air, the amount of which was determined from the percentage of oxygen present:--
ANALYSES OF BLACK-DAMP.
+--------------------------------------------------------+---------+-------------+ | |Nitrogen |Carbonic Acid| | LOCALITY. |per cent.| per cent. | +--------------------------------------------------------+---------+-------------+ |Stopping, Podmore Hall Colliery, North Staffordshire | 87.87 | 12.13 | |Another Stopping, same Colliery | 91.37 | 8.63 | |Main Return, same Colliery | 87.30 | 12.70 | |Sladderhill Colliery, Apedale, North Staffordshire | 85.86 | 14.14 | |Old Road, Talk o’ the Hill Colliery, North Staffordshire| 91.90 | 8.10 | |Main West Return, Talk o’ the Hill Colliery | 80.66 | 10.31 | |South Main Return, Great Fenton Col., N. Staffordshire | 89.31 | 12.69 | |Return, Wallsend Colliery, Newcastle, New South Wales | 89.00 | 11.00 | |Old Workings, Burghlee Colliery, Midlothian | 86.90 | 13.10 | |Upcast Shaft, same Pit | 86.91 | 13.09 | |Upcast Shaft, Tylorstown Colliery, South Wales | 85.97 | 14.03 | |Old Road, Conygre (Timsbury) Colliery, Somerset | 84.92 | 15.08 | |Stopping, Nabb Pit, Lilleshall Colliery | 86.48 | 13.52 | |Stopping, Hamstead Colliery, South Staffordshire | 93.25 | 6.75 | |Upcast Shaft, Hamstead Colliery, South Staffordshire | 93.31 | 6.69 | |Old Road, Forge Ironstone Pit, North Staffordshire | 85.30 | 14.70 | |Issuing from Hole, Foxdale Lead Mine, Isle of Man | 88.07 | 11.93 | |Issuing from another Hole, same Mine | 79.80 | 21.20 | |Return Air-way, same Mine | 80.30 | 19.70 | |Well at Redwick, Gloucestershire | 95.80 | 4.20 | |Coming over Top, Well at Balcombe, Sussex | 88.93 | 11.07 | |Well at Charterhouse School, Surrey | 81.86 | 18.14 | |Well at Northleigh, Oxfordshire | 93.19 | 6.81 | +--------------------------------------------------------+---------+-------------+
The black-damp met with in coal-pits is probably formed chiefly and often exclusively from the oxidation of iron pyrites (FeS_{2}) present in the coal. This is oxidised to sulphuric acid and sulphate of iron, and as carbonate of lime (calcite) is also present in the coal, the sulphuric acid usually combines with the lime, liberating carbonic acid. The whole process may be represented by the following equation:--
4FeS_{2} + 15O_{2} + 8CaCO_{3} = 8CO_{2} + 8CaSO_{4} + 2Fe_{2}O_{3}.
Oxidation occurring according to this equation would yield black-damp consisting of 87.7 per cent. of nitrogen and 12.3 per cent. of carbonic acid, which is nearly the composition usually found. On pieces of coal which have been exposed for some time to air and moisture the red oxide of iron resulting from this reaction may frequently be seen. On other pieces where there is no carbonate of lime, crystals of sulphate of iron, and an acid reaction will be found in the positions previously occupied by iron pyrites, while the coal itself is unchanged. The oxygen of air left in contact with coal gradually disappears. Hence old workings or spaces of any kind left unventilated soon become filled with black-damp. A fall in barometric pressure leads to an issue of black-damp from these spaces, though often there is also a constant issue into the return air-ways on account of a little air being sucked through from the intakes. In the case of wells the influence of barometric pressure on the issue of black-damp is very marked. The black-damp is formed in the pores of the surrounding strata, and issues out up the well whenever a fall of pressure occurs. Thus the well may be fairly clear of black-damp at one time, and shortly afterwards full of it. Accidents to well-sinkers commonly occur through ignorance of this fact. The air is perhaps tested in the morning with a candle and found clear. In the afternoon after dinner a further test is neglected, and if the barometer has meanwhile fallen, the well-sinkers may descend into black-damp and be asphyxiated or fatally injured, or drowned by falling from the ladder. In the case of wells and metalliferous mines the black-damp is probably formed partly by the oxidation of carbonate of iron.
The return air of coal mines always contains black-damp, about 2 per cent. being very commonly present in the air of the upcast shaft. As the air-current passing through a coal mine is enormous, the quantity of black-damp formed in the pit is very considerable, usually amounting to over 2000 cubic feet per minute in a large pit. The oxidation thus represented must liberate a large amount of heat in the mine. Thus in the case of one pit investigated by the writer and Mr F. G. Meachem[133] the amount of heat calculated as being liberated in the mine per minute would have sufficed to raise one ton of water 134° F. or to heat the whole of the air-current (of 100,000 cubic feet per minute) to boiling point. Of this heat only about one-ninth was expended in raising the temperature of the air, two-ninths became latent through evaporation of moisture, and the remaining six-ninths escaped by conduction into the surrounding strata. This slow oxidation is one of the main causes of the high temperatures met with in mines; and apart from it very deep workings could be kept comparatively cool by ventilation. It must, however, be borne in mind that air in descending the shaft of a pit is heated by compression about 5½°F. for every 1000 feet of descent. There is thus a limit to the cooling effect of ventilation. Moreover, at great depths oxidation is apt to be favoured by both the higher temperature and the crushing of the coal by the weight of superincumbent strata, since in coal which is crushed a much larger surface is exposed to the oxygen of the air. When a current of air insufficient to carry off the heat passes through crushed coal spontaneous combustion is very apt to occur, and is a source of constant danger in some seams.
Black-damp is ordinarily recognised by its action in extinguishing a candle or lamp. The percentage which is just extinctive to a tallow candle or miners’ safety lamp was carefully determined by Mr Atkinson and the writer. We found that a candle held vertically will not continue to burn if more than 15.8 per cent. of black-damp is present (corresponding to an oxygen percentage of 17.6 per cent.): that 17.7 per cent. of black-damp extinguished an ordinary safety lamp; and that 18.6 per cent. extinguished a candle held horizontally. The extinction is due, practically speaking, to the reduction in the oxygen percentage of the air and not to the presence of carbonic acid, although dilution of air with carbonic acid extinguishes a light somewhat sooner than dilution with nitrogen. A light will still just burn in a mixture of 75 per cent. of carbonic acid and 25 per cent. of oxygen. The presence of black-damp affects the light given by a candle long before the point of extinction is reached. The flame becomes smaller, and the rate of combustion is diminished. Angus Smith[134] found that when a candle was allowed to burn in air increasingly vitiated by its own combustion and by respiration, the light diminished to 22 per cent. of its original value when the oxygen percentage fell to 18.5 (corresponding to 8.9 per cent. of black-damp).
The effects of black-damp on men are due partly to the carbonic acid, and partly to the diminished oxygen percentage accompanying the admixture of black-damp with the air. The influence of excess of carbonic acid and of deficiency of oxygen must therefore first be described separately.[135]
When carbonic acid is added to air no noticeable effect is produced until about 3 per cent. is present, when the breathing begins to be distinctly deeper and slightly more frequent. No other unpleasant effects are produced, even after a long exposure; and animals kept in air containing 3 per cent. of carbonic acid are unaffected in health. As the percentage of carbonic acid increases, the effects on the breathing become more and more marked, until at about 6 or 7 per cent. there is severe panting, the pulse-rate being also more frequent and vigorous, and the face being flushed. The sensation experienced is similar to that accompanying hard, muscular work. A long stay in air of this composition is followed by frontal headache. With 10 per cent. of carbonic acid the respiratory distress is very great, but with a still higher percentage a narcotic effect is produced, and the mind becomes confused. Animals sometimes die from long exposure to air containing about 25 per cent. of carbonic acid, but even 50 per cent. may not prove fatal for some time.
Diminution of the oxygen percentage of air usually causes no noticeable effect until the percentage falls to about 12, when the respirations begin to be just perceptibly deeper. At 10 per cent. the respirations are usually distinctly deeper, and the lips begin to become slightly bluish. At 8 per cent. the lips and face have more or less of a leaden blue colour, and usually the breathing is deeper and more frequent. In some persons, however, this is not the case, and nothing is noticed by the person breathing this vitiated air, although his face presents to a bystander a most alarming appearance. At 5 or 6 per cent. there is clouding of the senses, and loss of power over the limbs, and often complete loss of consciousness, which, to judge from experiments on animals, would probably soon end in death, either from gradual failure of the respiratory centre or from stoppage of the heart. The symptoms described are those observed when the breathing of the vitiated air is not accompanied by muscular exertion. The danger point is, however, reached much sooner when any muscular exertion, such as that of climbing, or even walking, is made. Even at 15 per cent. of oxygen there is often shortness of breath and dizziness on exertion, and when the oxygen percentage falls much further fainting is apt to occur, and this is probably the cause of many accidents in which men fall off ladders in vitiated air, and are fatally injured or drowned. When the oxygen percentage falls below 8 or 10 per cent. death may occur in consequence of muscular exertion. Air vitiated simply by diminution of the oxygen percentage of the air is exceedingly dangerous, for the reason that there are hardly any warning symptoms before life is imperilled; and were it not that a light is usually carried in such air, and that its extinction gives ample warning, since it occurs at about 17 per cent. of oxygen, accidents would be much more frequent.
Sudden exposure to air containing less than 3 or 4 per cent. of oxygen causes in men loss of consciousness within about forty seconds. This is followed by convulsions, and the respirations soon cease. The heart, however, continues to beat for some time longer, and during this period artificial respiration will still restore life.
A reference to the composition of black-damp will show that the effects produced by it are due, in most cases at least, to carbonic acid as well as to want of oxygen. When there is just sufficient black-damp present to extinguish a light no noticeable effect is, as a rule, produced, since there is 17 per cent. of oxygen, and usually not more than about 2 per cent. of carbonic acid. Occasionally, however, as in the case of two of the samples from Foxdale lead mines (see table), there will be as much as 3 or 4 per cent. of carbonic acid present, in which case the breathing will be slightly affected. With an increasing percentage of black-damp the panting due to carbonic acid will usually become more and more noticeable. Thus with 50 per cent. of black-damp there will commonly be about 6 per cent. of carbonic acid, and 10.5 per cent. of oxygen. The panting due to carbonic acid will, therefore, be very considerable. In some cases, however, as in the black-damp from Hamstead Colliery or Redwick Well, there will still be insufficient carbonic acid to produce panting, and the air will be already dangerous from deficiency of oxygen. With still larger percentages of black-damp, the symptoms from want of oxygen will predominate more and more, until at last with about 75 per cent., or 5 per cent. of oxygen, life can no longer be supported. Death is always due to want of oxygen, and not to the poisonous action of carbonic acid. The presence of carbonic acid diminishes the danger, as the panting caused by it not only gives warning of danger, but also increases the oxygen supply to the lungs, and thus wards off for a time the effects of the deficiency of oxygen.
Carbonic Acid.--There is no recorded case of evolution of pure carbonic acid in a mine in this country, but in one colliery district in France sudden outbursts of pure carbonic acid have occurred. The locality is a volcanic one, and possibly the carbonic acid may have originated from some such cause as the decomposition of limestone by silicates at high temperatures. The well-known case of the Grotto del Cane is one in which pure carbonic acid is evolved. The composition of a sample recently analysed by the writer from near the floor of the Grotto corresponded exactly to that of a mixture by diffusion of pure carbonic acid and air. The effects of pure carbonic acid have already been described, and are, of course, quite different from those of black-damp. According to Clowes, air containing 15 per cent. of carbonic acid is just sufficient to extinguish lights. Air of this composition would produce violent panting and partial loss of consciousness.
Fire-damp.--The gas known to miners as fire-damp is recognised by its forming with air explosive mixtures. So far as is known the fire-damp met with in English mines is always pure methane (CH_{4}), although in Germany ethane (C_{2}H_{6}) is also reported to occur in connection with certain kinds of coal. The writer has carefully examined many specimens of fire-damp from various English coalfields, but never found that it consisted of anything else but the methane described by previous observers. The presence of fire-damp in air is recognised by miners from the appearance over the ordinary flames of a lamp of a pale non-luminous “cap” of flame, similar in appearance to the non-luminous flame of a Bunsen burner, though much paler, unless the air is nearly explosive. From the size and distinctness of this cap, the percentage of fire-damp can be approximately determined. In testing for fire-damp the flame of the safety lamp should be lowered until only a small blue flame is left. The pale cap can then be better seen above the lamp flame. With very careful observation about 1 per cent. of fire-damp in the air can just be detected. With a hydrogen flame, as in the Clowes lamp, it is possible to detect as little as 0.2 per cent.[136] With increasing percentages of fire-damp, the cap becomes longer and more distinct, and passes right up the chimney when the air is nearly explosive. Air containing anything between about 5 and 13 per cent. of fire-damp is explosive.
Fire-damp is given off from coal, within which it is contained in a highly compressed state. Different seams of coal give off very different proportions of fire-damp. Those seams which give off much are known to miners as “fiery.” The amount of fire-damp contained in the coal seems to depend in large measure on the extent to which the strata above the coal are gas-tight. If fire-damp can escape upwards it drains off from the coal. Some idea of the enormous amount of fire-damp contained in fiery coal can be formed from the amount of fire-damp which escapes from the mine by the upcast shaft. This is chiefly given off from the coal as it is exposed in working, so that from the output of coal and fire-damp from the mine a rough estimate can be made of the proportion of fire-damp in the coal. In one mine, for instance, about 4500 cubic feet of fire-damp per minute were given off, with an output of about 1200 tons of coal per day, or nearly one ton per minute. It would thus appear that 4500 cubic feet of fire-damp per ton raised were given off, or 150 cubic feet of gas per cubic foot of coal.
The fire-damp met with in mines is commonly mixed with a large proportion of black-damp; and in consequence of this the fire-damp, though still capable of forming an explosive mixture when less air is present, may not be recognised unless very carefully looked for, as the lamp is extinguished before a prominent cap is visible. Such a mixture may easily be fired by striking a match in the midst of it, or by a blown-out shot in blasting. The mixture is lighter than air, whereas pure black-damp is nearly always heavier than air.
Fire-damp has no direct action on man. It only acts by diluting the oxygen of the air. When a mixture of 79 per cent. of fire-damp and 21 per cent. of oxygen is breathed it cannot be distinguished from air; and animals may be kept for long periods in a mixture of this composition. The action of a given mixture of fire-damp and air thus depends simply upon the oxygen percentage, any effect produced being merely due to want of oxygen, the symptoms of which have already been described. As fire-damp is lighter than air, a man affected by it will, on losing consciousness, usually fall into better air. Were it not for this, fatal accidents by asphyxiation with fire-damp would be much more common. It often enough happens that a man is temporarily overcome by putting his head upwards into a cavity filled with fire-damp. If the fire-damp contains little or no air loss of consciousness occurs suddenly, and without previous warning. Fatal accidents sometimes occur through a man incautiously advancing without a lamp up a road, during attempts to restore ventilation in a district of a mine which has become filled with fire-damp. So long as a lamp burns in air containing fire-damp not the slightest harm results from breathing the air.
After-damp.--The gas remaining in a mine at the place where an explosion has occurred is known to miners as “after-damp,” and is much dreaded on account of its poisonous properties. A careful examination, recently undertaken by the writer,[137] of the bodies of the men and horses killed in three colliery explosions resulted in showing that in almost every case, whether or not there were burns or other injuries, the actual cause of death was carbonic oxide poisoning. In many cases, however, the burns or other injuries would certainly have proved fatal apart from the carbonic oxide; and the result of a rough estimate was that, on an average of the three explosions, about 23 per cent. of those killed had received burns or other injuries sufficient to cause death. Only 46 per cent. were burnt or injured.
The symptoms of the rescuers who encountered after-damp were clearly those of carbonic oxide poisoning. Their lamps continued to burn in the poisonous air, and in some cases men were found dead with their lamps either still burning, or with the oil burnt out. The fact that a lamp continues to burn, which is an excellent test of the safety of air vitiated by black-damp or fire-damp, is thus no test of the safety of air vitiated by after-damp.
In the case of the great colliery explosions which cause such wholesale destruction of life, the explosion is almost invariably one of coal-dust, started either by blasting at dry and dusty places in the mine, or by small explosions of fire-damp. Slighter explosions may be due simply to ignition of fire-damp. When fire-damp or coal-dust ignites in presence of excess of air, the products of combustion are simply carbonic acid and water, along with a little sulphurous acid in the case of coal-dust. The reaction occurring when fire-damp ignites under these conditions is represented by the following equation:--
CH_{4} + 2O_{2} = CO_{2} + 2H_{2}O.
The after-damp from such an explosion in air would consist of 88.3 per cent. of nitrogen and 11.7 per cent. of carbonic acid; and with coal-dust a slightly higher proportion of carbonic acid would be present. When, however, the proportion of air present is insufficient for complete oxidation a certain amount of carbonic oxide is produced in place of part of the carbonic acid. As much as 4.5 per cent. may be present in the after-damp of an explosion of fire-damp. In a colliery explosion the fire-damp or dust must always be very irregularly distributed in the air, so that in some places there will be an excess of air, and in others an excess of fire-damp or dust. At many places the excess of gas or dust must be so great that no explosion at all can occur. The after-damp is thus a variable mixture of nitrogen, carbonic acid, and carbonic oxide, together with much air, and, in the case of dust explosions, a little sulphurous acid or sulphuretted hydrogen, and various products of the dry distillation of coal. These latter products give after-damp a characteristic unpleasant smell. The fact that sufficient oxygen to support life is left along the track of an explosion is shown by the fact that the bodies do not present the appearances seen in the rapid death which ensues in an atmosphere devoid of oxygen. Probably about 2 to 5 per cent. of carbonic oxide is usually contained in the pure after-damp of a colliery explosion. The gas met with by rescuers some hours, or perhaps days, after the explosion, is, of course, a mixture of after-damp with the black-damp and fire-damp which has accumulated in consequence of stoppage of the ventilation through the air current being short-circuited.
The action on men and animals of after-damp depends practically upon the carbonic oxide contained in it. Pure after-damp, containing no air, would of course cause death just as rapidly apart from the action of the carbonic oxide: but such after-damp unmixed with air is hardly met with.
Carbonic oxide or carbon monoxide (CO) is a very poisonous gas. Judging from experiments on animals, air containing anything more than 0.4 per cent. would, after a sufficient time, always cause death in a man, though anything over 0.2 per cent. would in many cases prove fatal. It has practically no smell or irritating properties by which its presence might be readily recognised, and its action is peculiarly slow and insidious. The first symptoms of carbonic oxide poisoning are usually dizziness, shortness of breath, and palpitation following any unusual exertion. Sometimes there is drowsiness, and sometimes unusual excitement similar to that produced by alcohol. When more of the gas is absorbed there is great failure of muscular power. The least exertion causes dizziness and fainting, and any serious exertion may prove fatal. At the same time the mind becomes more or less confused, although the person affected is not himself aware of any mental failure. The senses are also affected, and frequently there seems to be greater or less insensibility to pain, as miners who are partially stupefied by carbonic oxide are not infrequently seriously burnt by their lamps. The loss of muscular and sensory power gradually becomes more and more complete, until at last consciousness is entirely lost; and finally, with further absorption, death quietly ensues. There is no pain or serious discomfort at any stage. Recovery from slight carbonic oxide poisoning is usually accompanied by severe headache, nausea, and depression. When consciousness has been lost for a considerable time, recovery is very slow and uncertain. Death may occur from pneumonia after two or three days; and a variety of severe mental symptoms may persist for long periods. In cases where much muscular exertion has been attempted during exposure to the poison the heart appears to be often seriously affected.
In order to understand the very peculiar features presented by carbonic oxide poisoning it is necessary to consider the mode of action of this gas. The oxygen absorbed from the air in the lungs is normally taken up in the form of a loose chemical combination with the red colouring matter (hæmoglobin) of the blood corpuscles, and so carried by the circulation to the tissues, where it is used up. The hæmoglobin not only combines with oxygen, but is also capable of forming a much more stable compound with carbonic oxide, and, as was shown by Claude Bernard, hæmoglobin which is saturated with carbonic oxide cannot take up oxygen. Hence, when the hæmoglobin of a living animal is saturated to a certain extent with carbonic oxide, sufficient oxygen cannot be conveyed from the lungs to the tissues, and death occurs from want of oxygen.[138] Carbonic oxide has no other action than that due to its interference with the oxygen supply through the blood. Apart from its property of combining with the hæmoglobin it is a physiologically indifferent gas, like nitrogen; and it has no action on lower animals which do not possess hæmoglobin. The symptoms produced by it are therefore essentially the same as those described above as due to deficiency of oxygen in the air breathed. No noticeable symptoms are produced until the hæmoglobin is about a third saturated with carbonic oxide, and death does not usually occur until about 70 or 80 per cent. saturation has been reached. When, therefore, not much carbonic oxide is present in the air, a considerable time elapses before a sufficient quantity of the gas has been absorbed to produce symptoms. A man possesses on an average a weight of blood equal to ¹⁄₂₁ of his body-weight, or about 3 litres, and the hæmoglobin of this blood requires about 600 c.c. of carbonic oxide to saturate it. He breathes when at rest about 5 litres of air per minute. Hence, supposing that the air contains 0.2 per cent. of carbonic oxide, which is about the minimum quantity which will produce death, he can absorb only 10 c.c. per minute at the most. It must thus take at least twenty minutes, and actually takes a good deal longer, for distinct symptoms to be produced. During this interval, which will, however, be shorter when the man is breathing more rapidly in consequence of muscular exertion, he may advance far into an atmosphere poisonous from the presence of after-damp, and may consequently be unable to return.
It might be supposed that the presence of any proportion, however small, of carbonic oxide in air would ultimately prove fatal from gradual absorption of the gas by the blood. Actually, however, there is a maximum limit to absorption with any given percentage of carbonic oxide in air; for although the affinity of hæmoglobin for carbonic oxide is much stronger than for oxygen, yet if both gases are present, the hæmoglobin is shared between them in proportion, not only to the relative strengths of their affinities for hæmoglobin, but also to the relative percentages present of the two gases. Hence, although the affinity of carbonic oxide for hæmoglobin is nearly four hundred times as great as that of oxygen, yet if the percentage of carbonic oxide is very minute as compared with the percentage of oxygen, only a little of the hæmoglobin will combine with the carbonic oxide, and consequently no symptoms of poisoning will be produced, however long the exposure may be. Thus with less than about .03 per cent. of carbonic oxide in the air, the blood will never absorb enough of the gas to produce distinct symptoms; and with less than .2 per cent. life will hardly be endangered, although very severe symptoms may be produced.
In recovery from carbonic oxide poisoning, the gas is driven out from the blood through the lungs in consequence of the preponderating influence of the oxygen of the air; and in the course of several hours the blood will be again practically free from carbonic oxide. An hour of breathing fresh air will usually suffice to remove any dangerous excess of carbonic oxide, but if, as often enough happens in persons who have been rendered unconscious, the breathing is shallow, a much longer time may be needed unless artificial respiration has been employed. Carbonic oxide is not oxidised within the body, so that the only way in which it can be got rid of is through the lungs. The blood from which the carbonic oxide has been expelled is in no way injured. The expulsion of carbonic oxide during recovery from poisoning can be greatly hastened by the inhalation of pure oxygen, since its influence in driving out carbonic oxide from the blood is about five times as great as that of air, which only contains 20.9 per cent. of oxygen. Inhalation of oxygen has also another and immediate effect, however. In addition to the oxygen taken up in combination with hæmoglobin, the blood takes up in the lungs a little oxygen in simple solution, just as an equal volume of water would do. When pure oxygen is breathed, the quantity of this dissolved oxygen is increased five times, and is then sufficient to afford an important immediate supply of oxygen to the tissues. If an animal be placed in oxygen at two atmospheres’ pressure, carbonic oxide can be administered without harming it, since although its hæmoglobin becomes completely saturated with carbonic oxide, its blood carries enough oxygen in simple solution to support life.
The cause of death in carbonic oxide poisoning can always be determined by examining a drop of blood taken from the body, and comparing it with normal blood from a healthy person or an animal. The normal blood is diluted with water until the tint of the solution appears yellow; the suspected blood is then diluted until its depth of colour appears about the same. If death was due to carbonic oxide poisoning the latter solution will appear pink instead of yellow. By taking advantage of this difference of tint the percentage saturation of the hæmoglobin can readily be determined. Death often occurs, however, some hours or days after removal from the poisonous atmosphere, and in this case the blood will be free of carbonic oxide. Blood saturated with carbonic oxide has a red colour similar to that of arterial blood, hence the lips, cheeks, and other parts of the bodies of men who have died from carbonic oxide poisoning have often a pink colour similar to that seen in life.
In consequence of the restricted oxygen supply to the tissues during prolonged exposure to carbonic oxide, serious changes may be produced in the brain, heart, and other organs, and as a result of these changes recovery does not occur at once when the carbonic oxide disappears from the blood. Unconsciousness may persist, or relapses may occur, and death is not unfrequent several days after exposure to the poison.
The prompt recognition of the presence of carbonic oxide or after-damp in air is of much practical importance. As already remarked, the fact that a lamp continues to burn is no proof of the safety of air in which after-damp may be present, and elaborate chemical tests are hardly applicable in ordinary practice. A small warm-blooded animal, such as a mouse, or perhaps still better a small bird, may, however, be used to indicate the presence of any dangerous proportion of carbonic oxide. The oxidation processes in the small animal are enormously more rapid than in a man: consequently the small animal breathes and absorbs carbonic oxide much more rapidly. It therefore shows symptoms of poisoning in a fraction of the time necessary in the case of a man, although it is only about equally sensitive to a given percentage of the gas. Hence by watching the animal, timely warning may be obtained of the presence of enough carbonic oxide to cause danger to life. It must be remembered, however, that the animal may show no very evident signs when sufficient carbonic oxide is present to cause very distinct and unpleasant symptoms in a man, and that these symptoms may be aggravated to a dangerous extent by muscular exertion, such as that of hurrying back towards fresh air. Another circumstance which tends to suddenly intensify the symptoms of carbonic oxide poisoning is exposure to cold air, and this should be avoided as far as possible with persons who have begun to feel the effects of the gas.
When a man has been rendered unconscious by exposure to carbonic oxide or any other suffocative gas, the first thing to do, after his removal from the contaminated air, is to apply artificial respiration without a moment’s delay, if the breathing has stopped or is feeble.
Smoke.--Some of the most disastrous accidents in mines have been due to the poisonous action of smoke from underground fires. Fires may occur from an intensification of the spontaneous oxidation of coal, iron pyrites, cotton waste, etc., from the careless use of lights, from engines underground, or in consequence of an explosion of gas setting fire to brattice cloths, igniting blowers of gas, etc. In any case the occurrence of a fire underground is a source of extreme danger, especially when the timbering has become ignited. If the fire occurs on, or spreads to, an intake road the ventilation current carries the smoke over the mine, killing all those who are unable to avoid it. Smoke which has travelled some distance in a mine appears to lose its pungent smell, and deposits the suspended particles which ordinarily render it visible. This greatly increases the danger, as there is then nothing to give warning of its presence. Thus in the case of the Snaefell accident in 1897 a number of men descended into the shaft without their suspicions being in any way aroused until they had gone too far to be able to return.
The poisonous constituent of smoke is carbonic oxide. This was clearly established in the case of the Snaefell accident, where the timbering had caught fire.[139] A sample of the poisonous air collected by Mr Williams, Her Majesty’s Inspector of Mines, was found by the writer to contain 1.1 per cent. of carbonic oxide. Mr Williams fell over unconscious just after obtaining the sample, and was only restored through the prompt application of artificial respiration by his colleague, Mr Jones. Further evidence that carbonic oxide is the cause of death in underground fires was afforded by the medical examination of the bodies by Dr Burkitt in the recent fire at Whitwick Colliery.[140] There can be little doubt that carbonic oxide poisoning is also one of the most frequent causes of death in fires above ground. The writer recently examined the body of a man found dead in a sitting position in a house which was partially burnt in Oxford. Carbonic oxide poisoning was the cause of death. There were only a few superficial burns which had apparently been inflicted after death. The smoke from burning or smouldering wood is particularly dangerous, as the gas distilled from wood may contain about 30 per cent. of carbonic oxide, the large proportion of oxygen in wood favouring the production of carbonic oxide.
As regards the symptoms produced by smoke nothing need be added to what has already been said under the heading of after-damp.
White-damp, Gob-stink, Fire-stink.--Under one or other of these names is included by miners the poisonous gas given off from coal which has heated from spontaneous oxidation. Some seams of coal, such as the thick coal in South Staffordshire, or the Bulhurst seam in North Staffordshire, are particularly liable to heating, which readily occurs where the coal has become more or less disintegrated. If the coal is not actually red-hot there may be no distinct smell, and the poisonous gas would come under the designation of “white-damp.” The name “gob-stink” is derived from the fact that the heating usually occurs in the waste coal of a goaf or gob (the area from which the workable coal has been removed). The origin of the name “white-damp” is less clear.
Practically speaking, white-damp and gob-stink, or fire-stink, have the same properties as after-damp, and the poisonous constituent is again carbonic oxide, which the writer has found to be present in various samples. Occasionally, however, sulphuretted hydrogen is also present in formidable proportions. The latter gas is extremely poisonous, as little as .07 per cent. being capable of causing death. Air containing 0.2 per cent. kills warm-blooded animals within one and a half minutes. Its presence may be detected not only by its characteristic smell of rotten eggs, but also by the fact that when present in the proportion of more than about .01 per cent., it causes smarting of the eyes and general irritation of the air-passages.
Gases from Explosives.--The gases from some explosives are extremely poisonous, from the presence in them of carbonic oxide, sulphuretted hydrogen, or nitric peroxide. In coal mines, when the ventilation is everywhere good, it seldom happens that there is trouble from the gases from explosives; but in metalliferous mines and underground quarries cases of poisoning are not uncommon.
Gunpowder gives off on ignition carbonic acid and nitrogen, along with a variable, though much smaller, proportion of carbonic oxide and sulphuretted hydrogen, either or both of which gases may produce symptoms of poisoning.
Of the “high” explosives, nitro-glycerine, blasting gelatine, and roburite yield on detonation only carbonic acid and nitrogen, whereas gun-cotton, tonite, gelignite, and carbonite also give off carbonic oxide, and therefore require more care when the ventilation is defective.
The most serious accidents in mines from gases from explosives have been due to the accidental burning of high explosives, such as dynamite or gun-cotton. When substances of this class burn quietly instead of detonating, nearly the whole of the nitrogen is given off as nitric oxide (NO) instead of as free nitrogen. The nitric oxide at once combines with the oxygen of the air to form nitric peroxide, which is a very dangerous gas. Even when a charge is detonated for blasting purposes it may happen, particularly with badly made or roughly handled explosives, that part burns quietly and forms nitric peroxide. The latter is an irritant gas, but when sufficiently diluted may be breathed for some time without the person exposed to it being aware of his danger. Under such circumstances bronchitis of a very acute character is apt to occur after a few hours, and death often results. In the gold mines in India and the Transvaal, accidents involving the loss of as many as twenty men at a time have sometimes occurred in this way from dynamite catching fire underground, and serious injury to health may easily be caused by the fumes of imperfectly detonated high explosives where the ventilation is bad.
JOHN HALDANE.