Coal. Spontaneous combustion and explosions occurring in coal cargoes: their treatment and prevention. Also the prevention of fire or explosions in ships, etc. (Appendices.)

Front matter

(tal SPONTANEOUS COMBUSTION AND EXPLOSIONS OCCURRING in COAL CARGOES: TLhciv treatment ano prevention. ALSO THE PREVENTION OF FIRE OR EXPLOSIONS IN SHIPS FROM CARGOES OR STORES CONTAINING SUBSTANCES OF A VOLATILE AND INFLAMMABLE NATURE. BY THOMAS ROWAN, (Consulting Engineer) Author of "An Examination of the * Flame' of the Hessemer Converter;" "The Estimation of Manganese in Ferro-Manganese ;" "The Molecular Action of Impurities in Iron,'/ &c. London: E. and F. N. SPON, 16, Charing Cross. New York : 44, Murray Street. 1S82 Hutborities Consulted or IReferreo to. Report ok the Royal Commissioners appointed to enquire into the Spontaneous Combustion op Coal in Ships. (1876). Percy : Metallurgy, Fuel, &c. Watts : Dictionary of Chemistry, &c. Ures : Arts and Manufactures. Bloxam's Chemistry. Miller's Chemistry.

Gmelin's Chemistry. Page's Geology. Roscoe and Schorlemmer : Treatise on Chemistry. Dana : Manual of Geology. R. C. Taylor : Statistics of Coal, Humble: Dictionary of Geology and Mineralogy. Atkinson : Gases met with in Coal Mines. J. W. Thomas : Coal-mine Gases and Ventilation. Major Majendie : Report of the Explosion of Gunpowder in the Regents Park (1875.) Official Report of the Loss of the "Amazon" (1852). Parliamentary Returns. 3n preparation, by> tbe same Hutbor. A TREATISE ON VENTILATION i T N which the Author describes his system of Ventilating the Sewers of Towns with the disinfection of the Sewer Gas — The Ventilation of House Sewers and Drains, &c. The Ventilation of Rooms and Buildings. How to insure a constant supply of pure air of uniform temperature, etc Hospital Ventilation. — The Ventilation of the Wards for Small Pox and other Infectious cases — Ventilation of Wards for Consumption and Pulmonary Complaints, &c.

Preface

. Attention has never been directed with, perhaps, greater interest than at the present time to the subjects which I have endeavoured to deal with in these pages — After the Royal Commission of 1875, appointed to enquire into the spontaneous combustion of coal in ships, expectations were formed that, at last, measures would be devised for minimising, at least, the risks which have attended the carriage of coal in ships. How far this has been accomplished will be seen from statistics given at Pages 28 and 34, and also Appendix D. An examination of the subject now has the great advantage of reviewing the labours and testing the value of the "suggestions" contained in the Report of the Royal Commission, of 1875, by the results which have followed, and thus ascertaining how far those " suggestions " have produced any practical benefit, and where they have failed.

I have also in Chapter IV. and Appendix F considered the carrriage on board ship of substances like naphtha, turpentine, benzoline, petroleum, &c, which readily yield vapours, which, on admixture with air, are not only dangerous on account of their explosive character, but of their inflammability and power of conveying flame considerable distances, to — it may be — vital parts of the ship or cargo. In doing this I have also directed attention to conditions still existing in ships of the navy and merchant vessels, which are liable to repeat these actions which occasioned the loss of H.M.S. " Doterel." I also point out that banishment of xerotine siccative merely gives no guarantee of immunity from similar accidents ; but that the conditions able to produce them will continue to be present, so long as substances containing naphtha, turpentine, benzoline, petroleum, &c, are carried as cargoes or stores, without adequate precautionary measures being enforced.

I have to acknowledge the courtesy of Thomas Gray, Esq., Assistant-Secretary to the Marine Department of the Board of Trade, who most kindly has permitted me to make use of an interesting and most suggestive memorandum, prepared by him relating to " Spontaneous Combustion of Coal, and Explosions of Coal Gas on Board Ship." I have also to thank my friend, Charles Anderson, Esq., of Manchester, for the assistance he has so efficiently rendered me in the revision and correction of proofs, &c. THOMAS ROWAN. Moslev Street, Manchester; Colmshill Street, Eaton Squark, London, s.w. ; May, 1882. CONTENTS.

Chapter I. Page

The Origin of Coal. — Its Geological Position. — Its Varieties. — The Gases Enclosed. — The Weathering of. — The Moisture Contained in. — The Absorbing Power of -------- i

Chapter II

The Royal Commission of 1875. — The Increase of Rates for Underwriting Coal Cargoes. — The Dangers Attending the Carriage and Stowage of Coal. — The Action Producing Spontaneous Combustion in Cargoes. — Sulphur in Coal. — Carbonaceous Oxidation of Coal. — Moisture and Oxidation. — Dr. Percy on Carbonaceous Oxidation. — Richters' Experiments. — Professor Ferguson's Experiments. — Examination of Report of the Royal Commission of 1S75. — The Proportion of Accidents Increases with the Tonnage of the Cargoes. — All Varieties of Coal Subject to Spontaneous Combustion. — The Effect of Moisture. — The Commencement of Spontaneous Combustion in Coal Cargoes. — The Indications given of Spontaneous Combustion. — The Smell Arising from it. — An Examination of Mr. Thomas's Treatise on Spontaneous Combustion in Coal Cargoes - - - 8

Chapter III

The Treatment of Coal Cargoes in Relation to Spontaneous Combustion. — The Suggestions given in the Report of the Royal Commission as to the Prevention of Spontaneous Combustion in Cargoes. — An Examination of the Practical Result of these Suggestions since their Publication as to the Occurrences of such Cases in Ships. — The Treatment of Coal Cargoes by "Abstractors." — The Special Treatment of Coal Known to be " Intrinsically Dangerous "--------.-. 27

Chapter IV

The Treatment of Coal Cargoes in Relation to Explosions of Gas from Coal. — The Chemistry of Fire-damp. —The Explosive Force Exerted by it. — Air and an Open Light Required to Explode it. —The Danger of Explosions in Coal Cargoes Greatest at First. — An Examination of the Practical Results of the Suggestions of the Royal Commission as to the Occurrence of Explosions. --Increase of such Accidents. — X PAGE. Want of Legislation on the Subject. —The Limit to Continuous Surface Ventilation. —The Danger of Leakage of Fire-damp from Coal Holds to Other Parts of the Vessel.— Not only Explosion to be Guarded Against, but the Conveyance of Flame by its Inflam mable Mixture with Air. — The Means to be Adopted to Prevent Explosions 32

Chapter V

, The Prevention of Fire or Explosions in Ships from Cargoes or Stores Containing Substances of a Volatile or Inflammable Nature. — Small Quantities of these Substances Render a Large Volume of Ail- Inflammable. — Such Accidents have been the Subject of Scientific Examination. —Professor Graham's Report on Loss of " Amazon." — Major Majendie's Report on the Explosion of Gunpowder in the Regent's Park.— The "Tilbury." — Memorandum of Experiments with Petroleum in Connection with Regent's Park Explosion. — Adequate Legislation Required. — Explosion on Board H.M.S "Triumph." — Xerotine Siccative. — All Substances Yielding Inflammable Vapours are in like manner Dangerous. — The Precautions to be Adopted - 38 APPENDICES.

Appendix

A. List of Questions and Replies Relating to Cases of Spontaneous Combustion in Coal Cargoes - - - - - - i. to xv.

APPENDIX.

B. Replies to the Query: What Time Usually Elapses Before Coal Newly- Raised from the Mine, is Shipped for Exportation ? - xvi. to xvii,

APPENDIX.

C. Extracts from the Statutory Inquiries held by Board of Trade, &c., given in the Appendix to the Report of the Royal Commission on Spontaneous Combustion of Coal in Ships - - . xviii. to xiii

APPENDIX.

C1 Cases of Explosions of Gas from Coal on Board Ship, Showing what Destructive Force may be Exerted by them.— Also Exhibiting the Danger to be Apprehended from the Leakage of Fire-damp xliii. to li

APPENDIX.

C-- PAGR, Cases Taken from Return, Printed by House of Commons, Showing the Time that has Elapsed from the Loading of Coal Vessels until Explosion has Taken Place Iii. to liii,

APPENDIX.

D. Tables Relating to Combustion and Explosion Table No. Ir Causes of Explosion in British-Owned Vessels. — Table No. 2 : Explosions of Gas in Coal Cargoes, in Long and Short Voyages, in British-Owned Vessels. — Table No. 3 : Total Number of Known Cases of Spontaneous Combustion, Occurring in British- Owned Vessels. — Table No. 4 : Explosions Reported in British - Owned Vessels During Ten Years. — Table No. 5 : No. of Coal-Laden Vessels which were Reported Missing During the Eleven Years Ending December 31st, 1880. — Table No. 6 : No. of Coal-Laden Vessels Reported Missing During Ten Years, Ending 31st December, 1S80, Distinguishing the Vessels which Sailed on Short Voyages from those which Sailed on Long Voyages, and also Distinguishing Steam-Ships from Sailing Ships - liv. to lvii

APPENDIX.

E, Tables Relating to Coal and Fuel Exports, Prices, &c. Table No. 7: Amount of Coal Exported and Coasted. — Table No. 8: Amount of Cinders Exported and Coasted. — Table No. 9: Amount of Patent Fuel Exported and Coasted. — Table No. 10 : Return Showing the Annual Average Price (Exclusive of City or other Dues) of the Best Coal at the Ship's Side in the Port of London, at per Chaldron, from 1820 to 1832, and at per Ton from 1832 to 1880 lviii. to lix.

APPENDIX.

F, Loss of H.M.S. "Doterel."— Finding of the Court-Martial.— Explosion on Board of H.M.S. "Triumph." — Xerotine Siccative Committee. — The Similarity of the Explosions on Board the "Doterel" and "Tilbury" Pointed Out. — Major Majendie's Report. — Remarks on the Conditions Now Existing on Board Ships of War and Merchant Vessels, which are Liable to a Repetition of Similar Disasters Ix, to COAL SPONTANEOUS COMBUSTION AND EXPLOSION ©ccurrino in Coal Cargoes THEIR TREATMENT AND PREVENTION.

Chapter I. Purpose

considering that action which results in what is termed the Spontaneous Combustion or Igni tion of Coal, more particularly as occurring in cargoes on board ship, as well as that other danger wliich Coal cargoes are exposed to, viz., the explosion (under certain con ditions) of Cas co-existing in Coal. Before proceeding to do this, I shall briefly touch on the formation or development of coal in the bowels of the earth — its geological position — its varieties — and mention a few chemical facts connected with it, in so far as they may bear on spontaneous combustion and explosion. In doing this my descriptions will not be framed in the technical language of a scientific thesis, but in plain popular terms, which I trust may be comprehended by all. ORIGIN OF COAL. Coal has been formed by the de composition or fermentation of vegetable matter under special conditions.

The products resulting from the decay of vegetable matter vary with the circumstances under which it progresses, viz., the free or limited access of air or. oxygen, the presence of moisture, and the incidents of temperature and pressure. If the decomposition of wood takes place with free access of air, the products are — carbonic acid water, "and, according to Hermann, a small proportion of nitrogen is absorbed and ammonia generated."'' If decomposition takes place with the exclusion of air, a small quantity of both carbonic acid and water are formed. * Miller. Spontaneous Combustion .in? Explosion and marsh gas, with similar hydro-carbon compounds, are pro duced in considerable quantities. The component elements of living vegetable matter are carbon, hydrogen, and oxygen, and these likewise are the constituents of coal, only in different proportions and altered relations.

The examination of a peat-bog will demonstrate the gradual and progressive changes that vegetable matter is undergoing from that in which the organic structure is present, to the dense black carbonized mass resembling true coal in all but its density. The ash from peat taken from the surface does not exceed 2 per cent., while that from the bottom of the peat-bog sometimes reaches upwards of 30 per cent.* We can also trace these changes undergone in the gradual transformation from the first variety of coal where fermentation is not completed, and where the evidences of its vegetable origin are unmistakeable, up to anthracite, where the fermentation of vegetable matter during its carbonization in the bowels of the earth has reached its utmost limits, and, as observed by Sir C. Lyell, " is so altered from its original vegetable condition as to leave scarcely any trace of its history."

The following table, extracted from Dr. Percy's work on Fuel, shows at a glance the changes that occur in the transformation of vegetable matter into anthracite : — Table showingthe gradual Changes in Composition from Wood to Anthracite. * -Miller. Substance. Carbon. Hydrogen. Oxygen. Disposable Hydrogen. I. Wood (the mean of several ) Analyses) j I0° 12-lS 87*07 i*8o 2. Peat (do. do.) ioo 9-85 55'67 2*89 3. Lignite (do. of 15 varieties).. 100 8-37 42-42 3-°7 4. Ten- Yard Coal from South ) Staffordshire basin { IO° 6"I2 21*23 3'47 5. Steam Coal from the Tyne... 100 5-91 l8-32 3-62 6. Pentrefelin Coal of S. Wales , 100 475 5-28 4-09 7. Anthracite from Pennsvl- ) vania, U.S \ IO° 2-84 174 2-63 Thus in the decomposition of vegetable matter during its gradual carbonization, the original elements (carbon, hydrogen, and oxygen) are slowly re-acting on one another, forming with one another these compounds — marsh gas, carbonic acid, and water, and exhi biting in the different degrees of fermentation different proportions of its original elements.

That these changes have not only been carried on through vast periods of time, but have been effected under conditions of tran quility, is made evident from a geological examination of the coal deposits, where the many fossilized plants are discovered in the most perfect condition. The trunks also of the Sigillaria are in many instances found in situ piercing the seams of coal and superincum bent strata, with their roots in the beds of clay which lie in contact with and immediately below the coal. Evidences, also, of an exceedingly hot climate are indicated by the fossil flora of the more ancient coal deposits, consisting mainly of large vascular plants of the Cryptogamic vegetation. Indeed I can conceive of no more fascinating page in the whole book of Nature, than that which is disclosed to us by an examination of these ancient relics and records of primeval life and vegetation with which our coal deposits are so enriched.

The late Professor Buckland remarks, in that graphic and grace ful language which distinguishes his writings — " We are all brought back into immediate connection with the vegetation that clothed the ancient earth, before one-half of its actual surface had yet been formed. The trees of the primeval forests have not, like modern trees, undergone decay, yielding back their elements to the soil and atmosphere by which they had been nourished ; but, treasured up in subterranean storehouses, have been transformed into enduring beds of coal, which, in these later ages, have become to man the sources of heat, and light and wealth. My fire now burns with fuel, and my lamp is now shining with the light of gas, derived from coal which has been buried for countless ages in the deep and dark recesses of the earth.

We prepare our food, and maintain our forges and furnaces, and the power of our steam-engines, with the remains of plants of ancient forms and extinct species, which were swept from the earth ere the formation of the transition series was completed. -I Spontaneous Combustion ano Explosion Thus, from the wreck of forests that waved upon the surface of the primeval lands, and from ferruginous mud that was lodged at the bottom of the primeval waters, we derive our chief supplies of coal and iron ; those two fundamental elements of art and industry, which contribute more than any other mineral productions of the earth, to increase the riches, and multiply the comforts, and ameliorate the condition of mankind." GEOLOGICAL POSITION OF COAL. In the modern arrangement of strata now accepted by Geologists, and founded on its mineral differences and fossil distinctions, we find the coal measures embraced in what is termed the Carboniferous system.

This system lies immediately above the Old Red Sandstone or Devonian system, and below the Permian system. The Car boniferous system has been divided into the lower coal measures or Carboniferous shales, the mountain limestones, and the upper or true coal measures. " On the whole," remarks Mr. Page, "the Carboniferous strata from first to last may be said to be composed of frequent alternations of sandstones, shales, fire-clays, lime stones, coals, and ironstones." " The influences," remarks another author, " which have determined the characters of the rocks that are associated with the coal beds have been so constant that not only are they identical all over the globe, but in the cases where coal beds are formed on other formations than the coal formations, the rocks of these formations abandon their special characters to borrow those we have described.

" ( Taylor. ) VARIETIES OF COAL. Leaving aside the consideration of peat and the several other varieties of fossilized combustible matters, such as resin, bitumen, &c, &c, coal has been divided into three leading varieties, viz. : — Lignite, Bituminous Coal, and Anthracite. Lignite. This variety of coal is to be found in that system embracing the strata and sedimentary accumulations which lie between the Chalk and the close of the Drift formation, called the Tertiary system. It is therefore of much more recent formation than common coal. Dr. Ure has observed that " Lignites, which are manifestly bituminized wood, hold an intermediate place in the gradation between vegetable matter and pit coal. They have the fibre of the former, with the jetty lustre of the latter. Some lignites closely resemble peats in their chemical characters ; others seem to graduate into perfect coal.

Lignite has generally a woody aspect ; coal always that of rock." Lignites all contain a large proportion of water when first raised, sometimes reaching 40 per cent., and they retain 15 or 20 per cent, of this after exposure to the air for even many months.* They vary in colour from brown to black. Some also retain their woody lamellar structure ; in others this is only with difficulty distinguishable. Iron pyrites is nearly always present in the different varieties of lignite. Bituminous Coal. This is the most abundant, as it is by far the most important, product of the British coal fields. There are a number of varieties of Bituminous coal differing con siderably in their composition, and in the products they yield by the application of heat. When placed on the fire they, however, all burn with a smoky flame, of more or less luminosity.

They never exhibit a crystallised fracture, and when heated in a closed vessel they leave a more or less coherent coke. The most important varieties of Bituminous coal are — 1. Cannel, or Parrot Coal, sometimes also named Gas coal. They are of a slatey structure. When placed in a heated retort from which air is excluded, they yield a large quantity of volatile matter, in the form of uncondensable gases and conden sable vapours ; the residue left in the retort being the well-known gas coke. Some varieties of Cannel coal, when gradually heated with exclusion of air, yield a considerable quantity of liquid and oily hydro-carbons, with gaseous hydro-carbons of more or less density. 2. The second variety may be represented by House Coal, such as Newcastle coal, and is much valued for domestic and for " Miller.

Spontaneous Combustion ano Explosion 6 heating purposes generally. This variety burns with a bright luminous flame, and yields a grey-black cellular coherent mass of coke, possessing much lustre. 3. Steam Coal. This third variety approaches anthracite in quality, and represents that point where the bituminous character is verging into the anthracite. It burns freely with flame, but with little smoke, giving out a steady heat. It stands considerable pressure without crumbling, and is therefore well adapted for carriage in the holds of steam vessels. The coke it yields pos sesses little coherency or lustre. Anthracite Coal. This is sometimes designated Stone coal, or Culm. It is, as we have already seen, the ultimate product of the decomposition or carbonization of vegetable matter. It is very compact and hard, burning often with considerable difficulty, and with a smokeless flame of feeble luminosity.

Many varieties of anthracite, when heated, splinter into small fragments or decrepitate, and are therefore inconvenient for household purposes. Anthracite is often iridescent, some varieties exhibiting so beau tiful an iridescent play of colours as to be termed " Peacock coal." The coke obtained from anthracite differs little either in bulk or weight from the original coal. It is exceedingly abundant in North America, and we can obtain an excellent quality of anthracite from the South Wales coal fields. The gases enclosed or occluded in coal, have been examined by several chemists of high reputation, and present a most interesting subject of study. As not being, however, within the scope of this treatise, I must refer the reader to Dr. Percy's valuable volume on Fuel, where this subject is dealt with in that thorough manner that characterises all Dr. Percy's work.

When coal is exposed to the weather for any lengthened period of time, it is found to have deteriorated in quality and value. To a great extent its calorific power has disappeared, and in some kinds of coal the caking qualities are much modified, if not altogether lost. If, however, coal is so protected as to be kept dry, this deterioration progresses but slowly. Richters has made very elaborate investigations into what he has termed, the " weathering " of coal. His results are most valuable and interesting. In these experiments he demonstrates the power possessed by coal for absorbing atmospheric oxygen — that this varies in different coal — that " the absorption begins very soon and progresses with proportionate rapidity,"* and is accelerated by heat. All coal is found to contain water or moisture, to a greater or less degree, when brought to the surface, a portion of which it loses when exposed to the air.

The power to absorb and retain mois ture varies considerably in different coal. It has been shown by Richter that this property is not dependent on its structure merely ; a compact coal sometimes absorbing three times more moisture than a coal of a soft loose texture. He also showed that a relation existed between the absorbent power of coal for water and oxygen — that the more water a coal could injest the greater its absorbent power for oxygen. Percy.

Chapter II. He

safe carriage of coal in ships is a subject of deep interest, not merely to coal shippers and those more directly concerned in its export, but to the nation at large. If, therefore, from a study of the subject, we can arrive at the direct causes of these accidents, which render coal a most dangerous and treacherous cargo, and are thus enabled to indicate means by which coal can be conveyed in ships with safety, there can be but few more important investigations. The great importance of this question has always been recognized, and increasingly so of late. A Royal Commission was appointed by Parliament in 1875, to inquire into the spontaneous combustion of coal in ships, and in 1876 their report was issued in the form of one of the blue books. A perusal of the cases given in it will show what severe casualty constantly accompanies the carriage of coal in ships.

The conclusions arrived at from the inves tigation of the cases of spontaneous combustion and ex plosion submitted to them, the result of their examination of witnesses directly concerned in them, or in the subject, and their collection of collateral evidence received from other sources, were summarized by the Commissioners in their report, under seven heads, lo which I shall again refer. I will only here observe that up to the present time the risks attendant on coal carriage have not been reduced,1' at least in the judgment of the Underwriters, and the premiums on underwriting coal cargoes, which in 1875 were described as being almost prohibitive for long voyages, far from being reduced, have again increased. Taking for example such a port as Liverpool, the rates since December, 1881, have increased 5s. to 10s. per cent.

And at * Page Hull the underwriters decline to quote for long voyages unless for " sporting risks." The dangers to which the carriage and stowage of coal are sub ject, are twofold, viz. : — Spontaneous Combustion and Explosion. I shall proceed to investigate these points, and to draw attention to what in my opinion is necessary to be effected in order that coal on board ship may be conveyed with immunity from disastrous accident. Spontaneous Combustion. The result of all sound research into those chemical changes which cause (so called) spontaneous combustion or ignition of coal, is to demonstrate that it can arise from two sources.* ist. The oxidation of some of the sulphur compounds existing in coal. 2nd. The absorption and condensation of atmospheric oxygen by the carbon pores of coal — otherwise carbonaceous oxidation.

Under certain conditions, which we will examine, both of these actions take place, accompanied with the evolution of heat, and, if carried on with sufficient energy, such elevations of temperature can be induced as to result in the ignition or combustion of the coal. Sulphurs in coal is found in two forms of combination — as a sul phide, as in pyrites — or as a sulphate, as in sulphate of lime. In the latter form, it is stable, and being already completely oxidized, it cannot develop heat. The chief, if not the only form of sulphur in coal which gives rise to spontaneous combustion, is its com bination with iron, known as iron-pyrites, or " brasses." This combination of sulphur is more or less present in every variety of coal. Sometimes it occurs in massive forms or laminæ, sometimes in fine filaments, and sometimes in minute crystals.

Pyrites is known to exist in the mineral kingdom in the cubical form, having *The oxidation of the " disposable hydrogen " has been suggested as a pro bable source of heating — this, however, as yet, is merely hypothetical. + Sulphur may exist in combination with the organic elements of coal, but the exact relations that may be established between them is unknown. auo Ejplosion 10 a bright yellow colour — or in the prismatic form exhibiting a while metallic appearance. With the varying physical conditions under which pyrites exist in coal, so does its stability alter some forms of pyrites readily commencing oxidation on free exposure to the atmosphere, while others require some exciting cause — such as heat — before oxidation begins. In all cases, moisture promotes this oxidation, if indeed its presence is not absolutely essential to its taking place at all.

The oxidation of pyrites is always slow, and its rate ot pro gression is also commensurately slow. This action has therefore to be conducted on sufficient mass before the accumulated heat can so accelerate the oxidation as to arrive at temperatures requisite for ignition. We have already seen that coal has the power, more or less, of absorbing atmospheric oxygen. With some varieties of coal tlie action can also result in ignition. This occurs with charcoal, if stacked soon after its preparation ; the highly porous structure of the charcoal offering especially favourable conditions for rapid absorption. Coal presents great variety in structure and texture, some being upen and porous, others compact. Some varieties are soft and friable, crumbling with friction or pressure ; others again can resist considerable pressure without disintegration.

In my opinion, however, the mechanical conditions as presented in the average size of the lumps of which coal cargoes are made up, and the proportion their quantity bears to the amount of small coal mixed with them, are not such as tend, unaided, to promote carbonaceous uxidation with sutficient rapidity to cause ignition ; and, there fore, in the majority of cases, the spontaneous combustion of coal on board ship has, in the first instance, been due to other causes. The experiments of Richters show that coal, under certain conditions, can spontaneously ignite from solely carbonaceous oxidation. The following table, which I have taken from Dr. Percy's work on " Fuel," shows the results of Richters' experiments on the ignition of coal from carbonaceous oxidation. I will also give Dr. Percy's observations regarding them — " In a lecture delivered in 1864 I used these words when speaking about coal: 'I am disposed to believe that there is another cause of spontaneous ignition (besides iron-pyrites) similar to that which determines the spontaneous combustion of cotton waste, viz.: — the absorption of oxygen by coal reduced to a fine state of division;' and I had often previously stated the same view in my lectures at the Royal School of Mines It was reserved for Richters to substitute fact for opinion, and to demonstrate by experiments — which, in my judgment, are conclusive — that, generally, the spontaneous ignition of coal is due to the heat developed by atmospheric oxidation of the organic substance of coal, and not lo that resulting from the oxidation of iron-pyrites.

He has shown that coal most liable to spontaneous ignition is not that which contains most iron-pyrites ; and of this proof is afforded by the following table, in which he has arranged eleven varieties of coal from the carboniferous system, in three classes, according to the degree of their self-inflammability : — Table of Coals arranged according to degree of Self-Inflammability. Degree of Self-Inflammability. Iron Pyrites, WfJ^r' Character percent. of Coal. Class I. Difficultly Self-Inflammable ... 1*13 2 -54 Easily friable. i from j y compacti ' ro1 to . 2-7. 1 3'04 ( 275 ( 1*51 ) 3*90 Do. 3 Class II. Of Medium \ * Self-Inflammability j 5 1*20 4'50 Finn, schistose, bright. I *o8 4*55 f Hard, but very brittle. I -15 4*75 Moderately tender. i 7 I 8 Class III. Readily] 9 Self-Inflammable ...