Science in short chapters

Front matter

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0 1 37 20

Preface

This book supplies a growing want of these busy times, when so many of us are prevented by the struggles of business from sitting down to the consecutive systematic study of a formal treatise.

I have kept this demand steadily in view throughout, by select¬ ing subjects which are likely to be interesting to all readers who are sufficiently intelligent to prefer sober fact to sensational fiction, but who, at the same time, do not profess to be scientific specialists.

In the writing of these papers my highest literary ambition has always been to combine clearness and simplicity with some attempt at philosophy.

W. M. W.

Willesden, September, 1883.

Publishers1 Note to the American Edition.

This edition, prepared for American readers, contains tlie com¬ plete text of the English edition ; nothing has been omitted ; but the order of the articles has been changed so as to make a more interesting arrangement of the subjects.

New York, January 15, 1883.

Contents

Another World Down Here, . . .

Concert-room Acoustics, ....

Origin of Soap, .....

Chapter I. Another World Down Here

What a horrible place must this world appear when re¬ garded according to our ideas from an insect’s point of view ! The air infested with huge flying hungry dragons, whose gaping and snapping mouths are ever intent upon swallowing the innocent creatures for whom, according to the insect, if he were like us, a properly constructed world ought to be exclu¬ sively adapted. The solid earth continually shaken by the approaching tread of hideous giants — moving mountains — that crush our precious lives at every footstep, an occasional draught of the blood of these monsters, stolen at life-risk, affording but poor compensation for such fatal persecution.

Let us hope that the little victims are less like ourselves than the doings of ants and bees might lead us to suppose ; that their mental anxieties are not proportionate to the optical vigilance indicated by the four thousand eye-lenses of the common house-fly, the seventeen thousand of the cabbage but¬ terfly and the wide-awake dragon-fly, or the twenty-five thous¬ and possessed by certain species of still more vigilant beetles.

Each of these little eyes has its own cornea, its lens, and a curious six-sided, transparent prism, at the back of which is a special retina spreading out from a branch of the main optic nerve, which, in the cockchafer and some other creatures, is half as large as the brain. If each of these lenses forms a separate picture of each object rather than a single mosaic picture, as some anatomists suppose, what an awful army of cruel giants must the cockchafer behold when he is captured by a schoolboy !

* The order of the articles has been changed in this edition. See Publishers’ note on page 4.

SCIENCE IN SHORT CHAPTERS.

The insect must see a whole world of wonders of which we know little or nothing. True, we have microscopes, with which we can see one thing at a time if carefully laid upon the stage ; but what is the finest instrument that Ross can produce compared to that with twenty-five thousand object-glasses, all of them probably achromatic, and each one a living instru¬ ment, with its own nerve-branch supplying a separate sensa¬ tion ? To creatures thus endowed with microscopic vision, a cloud of sandy dust must appear like an avalanche of massive rock-fragments, and everything else proportionally monstrous.

One of the many delusions engendered by our human self-conceit and habit of considering the world as only such as we know it from our human point of view, is that of supposing human intelligence to be the only kind of intelligence in exist¬ ence. The fact is, that what we call the lower animals have special intelligence of their own as far transcending our in¬ telligence as our peculiar reasoning intelligence exceeds theirs. We are as incapable of following the track of a friend by the smell of his footsteps as a dog is of writing a metaphysical treatise.

So with insects. They are probably acquainted with a whole world of physical facts of which we are utterly ignorant. Our auditory apparatus supplies us with a knowledge of sounds. What are these sounds ? They are vibrations of matter which are capable of producing corresponding or sympathetic vibra¬ tions of the drums of our ears or the bones of our skull. When we carefully examine the subject, and count the number of vibrations that produce our world of sounds of varying pitch, we find that the human ear can only respond to a limited range of such vibrations. If they exceed three thousand per second, the sound becomes too shrill for average people to hear it, though some exceptional ears can take up pulsations or waves that succeed each other more rapidly than this.

Reasoning from the analogy of stretched strings and mem¬ branes, and of air vibrating in tubes, etc., we are justified in concluding that the smaller the drum or the tube the higher will be the note it produces when agitated, and the smaller and the more rapid the aerial wave to which it will respond. The drums of insect ears, and the tubes, etc., connected with them, are so minute that their world of sounds probably begins where ours ceases ; that the sound which appears, to us as con¬ tinuous is to them a series of separated blows, just as vibrations of ten or twelve per second appear to us. We begin to hear ahothek world dowh SERE.

such vibrations as continuous sounds when they amount to about thirty per second. The insect’s continuous sound prob¬ ably begins beyond three thousand. The blue-bottle may thus enjoy a whole world of exquisite music of which we know nothing.

There is another very suggestive peculiarity in the auditory apparatus of insects. Its structure and position are something between those of an ear and of an eye. Careful examination of the head of one of our domestic companions*— the common cockroach or black-beetle — will reveal two round white points, somewhat higher than the base of the long outer antennse, and a little nearer to the middle line of the head. These white projecting spots are formed by the outer transparent membrane of a bag or ball filled with fluid, which ball or bag rests inside another cavity in the head. It resembles our own eye in hav¬ ing this external transparent tough membrane which corre¬ sponds to the cornea or transparent membrane forming the glass of our eye-window ; which, like the cornea, is backed by the fluid in an ear-ball corresponding to our eyeball, and the back of this ear-ball appears to receive the outspreadings of a nerve, just as the back of our eye is lined with that out¬ spread of the optic nerve forming the retina. There does not appear to be in this or other insects a tightly stretched mem¬ brane which, like the membrane of our ear-drum, is fitted to take up bodily air-waves and vibrate responsively to them. But it is evidently adapted to receive and concentrate some kind of vibration, or motion, or tremor.

What kind of motion can this be ? What kind of per¬ ception does this curious organ supply ? To answer these questions we must travel beyond, the strict limits of scientific induction and enter the fairyland of scientific imagination. We may wander here in safety, provided we always remem¬ ber where we are, and keep a true course guided by the com¬ pass-needle of demonstrable facts.

I have said that the cornea-like membrane of the insect’s ear-bag does not appear capable of responding to bodily air¬ waves. This adjective is important, because there are vibratory movements of matter that are not bodily but molecular. An analogy may help to render this distinction intelligible. I may take a long string of beads and shake it into wavelike move¬ ments, the waves being formed by the movements of the whole string. We may now conceive another kind of movement or vibration by supposing one bead to receive a blow pushing it

SCIEKCE Itf SHORT CHAPTERS.

forward, this push to be communicated to the next, then to the third, and so on, producing a minute running tremor passing from end to end. This kind of action may be rendered visible by laying a number of billiard balls or marbles in line and bowling an outside ball against the end one of the row. The impulse will be rapidly and invisibly transmitted all along the line, and the outer ball will respond by starting forward.

Heat, light, and electricity are mysterious internal move¬ ments of what y?e call matter (some say “ ether,” which is but a name for imaginary matter.) These internal movements are a^ invisible as those of the intermediate billiard balls ; but if there be a line of molecules acting thus, and the terminal one strikes an organ of sense fitted to receive its motion, some sort of perception may follow. When such movements of certain frequency and amplitude strike our organs of vision, the sensa¬ tion of light is produced. When others of greater amplitude and smaller frequency strike the terminal outspread of our common sensory nerves, the sensation of heat results. The difference between the frequency and amplitude of the heat waves and the light waves is but small, or, strictly speaking, there is no actual line of separation lying between them ; they run directly into each other. When a piece of metal is gradually heated, it is first “ black-hot this is while the weaves or molecular tremblings are of a certain amplitude and frequency ; as the frequency increases and amplitude dimin¬ ishes (or, to borrow from musical terms, as the pitch rises), the metal becomes dull red-hot ; greater rapidity, cherry red ; greater still, bright red ; then yellow-hot and white-hot : the luminosity growing as the rapidity of molecular vibration increases.

There is no such gradation between the most rapid undula¬ tions or tremblings that produce our sensation of sound and the slowest of those w?hich give rise to our sensations of gentlest warmth. There is a huge gap between them, wide enough to include another world or several other worlds of motion, all lying between our world of sounds and our world of heat and light, and there is no good reason whatever for supposing that matter is incapable of such intermediate activity, or that such activity may not give rise to intermediate sensa¬ tions, provided there are organs for taking up and sensifying (if I may coin a desirable word) these movements.

As already stated, the limit of audible tremors is three to four thousand per second, but the smallest number of tremors

ANOTHER WORLD DOWN HERE.

that we can perceive as heat is between three and four millions of millions per second. The number of waves producing red light is estimated at four hundred and seventy-four millions of millions per second ; and for the production of violet light, six hundred and ninety-nine millions of millions. These are the received conclusions of our best mathematicians, which I repeat on their authority. Allowing, however, a very large margin of possible error, the world of possible sensations lying between those produced by a few thousands of waves and any number of millions is of enormous width.

In such a world of intermediate activities the insect probably lives, with a sense of vision revealing to him more than our microscopes show to us, and with his minute eye-like ear-bag sensifying material movements that lie between our world of sounds and our other far-distant worlds of heat and light.

There is yet another indication of some sort of intermediate sensation possessed by insects. Many of them are not only endowed with the thousands of lenses of their compound eyes, but have in addition several curious organs that have been designated ‘ 4 ocelli ’ ’ and ‘ ‘ stemmata. ’ ’ These are generally placed at the top of the head, the thousand-fold eyes being at the sides. They are very much like the auditory organs above described — so much so that in consulting different authorities for special information on the subject I have fallen into some confusion, from which I can only escape by supposing that the organ which one anatomist describes as the ocelli of certain insects is regarded as the auditory apparatus when examined in another insect by another anatomist. All this indicates a sort of continuity of sensation connecting the sounds of the insect world with the objects of their vision.

But these ocular ears or auditory eyes of the insect are not his only advantage over us. He has another sensory organ to which, with all our boasted intellect, we can claim nothing that is comparable, unless it be our olfactory nerve. The possibil¬ ity of this I will presently discuss.

I refer to the antennce , which are the most characteristic of insect organs, and wonderfully developed in some, as many be seen by examining the plumes of the crested gnat. Every¬ body who has carefully watched the doings of insects must have observed the curiously investigative movements of the. antenna, which are ever on the alert, peering and prying to right and left and upward and downward. Huber, who devoted his life to the study of bees and ants, concluded that

SCIENCE IN SHORT CHAPTERS.

these insects converse with each other by movements of the antennae, and he has given to the signs thus produced the name of “ antennal language.” They certainly do communicate information or give orders by some means ; and when the insects stop for that purpose, they face each other and execute peculiar wavings of these organs that are highly suggestive of the movements of the old semaphore telegraph arms.

The most generally received opinion is that these antennae are very delicate organs of touch, but some recent experiments made by Gustav Hansen indicate that they are organs of smelling or of some similar power of distinguishing objects at a distance. Flies deprived of their antennae ceased to display any interest in tainted meat that had previously proved very attractive. Other insects similarly treated appear to become indifferent to odors generally. He shows that the develop¬ ment of the antennae in different species corresponds to the power of smelling which they seem to possess.

I am sorely tempted to add another argument to those brought forward by Hansen — viz. that our own olfactory nerves, and those of all our near mammalian relations, are curiously like a pair of antennae.

There are two elements in a nervous structure, the gray and the white ; the gray or ganglionic portion is supposed to be the centre or seat of nervous power, and the white medullary or fibrous portion merely the conductor of nervous energy.

The nerves of the other senses have their ganglia seated internally, and bundles of tubular white threads spread out¬ ward therefrom ; but not so with the olfactory nervous appara¬ tus. These present two horn-like projections that are thrust forward from the base of the brain, and have white or medul¬ lary stems that terminate outwardly or anteriorly in ganglionic bulbs resting upon what I may call the roof of the nose ; these bulbs throw out fibres that are composed, rather paradoxically, of more gray matter than white. In some quadrupeds with great power of smell, the olfactory nerves extend so far for¬ ward as to protrude beyond the front of the hemispheres of the brain, with bulbous terminations relatively very much larger than those of man.

They thus appear like veritable antennae. In some of our best works on anatomy of the brain (Solly, for example) a series of comparative pictures of the brains of different animals is shown, extending from man to the cod-fish. As we proceed downward, the horn-like projection of the olfactory nerves

ANOTHER WORLD DOWN HERE.

beyond the central hemispheres goes on extending more and more, and the relative magnitude of the terminal ganglia or olfactory lobes increases in similar order.

We have only to omit the nasal bones and nostrils, to con¬ tinue this forward extrusion of the olfactory nerves and their bulbs and branches, to coat them with suitable sheaths provided with muscles for mobility, and we have the antenme of insects. I submit this view of the comparative anatomy of these organs as my own speculation, to be taken for what it is worth.

There is no doubt that the antennae of these creatures are connected by nerve-stalks with the anterior part of their supra-sesophageal ganglia — i.e. the nervous centres correspond¬ ing to our brain.

But what kind and degree of power must such olfactory organs possess ? The dog has, relatively to the rest of his brain, a much greater development of the olfactory nerves and ganglia than man has. His powers of smell are so much greater than ours that we find it difficult to conceive the possi¬ bility of what we actually see him do. As an example I may describe an experiment I made upon a bloodhound of the famous Cuban breed. He belonged to a friend whose house is situated on an eminence commanding an extensive view. I started from the garden and wandered about a mile away, crossed several fields by sinuous courses, climbing over stiles, and jumping ditches, always keeping the house in view ; I then returned by quite a different track. The bloodhound was set upon the beginning of my track. I watched him from a window galloping rapidly, and following all its windings without the least halting or hesitation. It was as clear to his nose as a gravelled path or a luminous streak would be to our eyes. On his return I went down to him, and without approaching nearer than five or six yards he recognized me as the object of his search, proving this by circling round me, baying deeply and savagely though harmlessly, as he always kept at about the same distance. *

* What did he smell ? Was it an emanation from the soles of my feet? If so, how did this aura get through the soles of my boots, which were thick ? It could scarcely have been the odor of the boot soles themselves that he followed, as he recognized me afterward at some distance. This suggests an interesting experiment, that any¬ body owning one of these dogs may easily try. Make a similar track to mine, but when on the way, take off the boots you wore on start¬ ing and change them for some one else’s boots, or a new pair, and watch the result from the window.

SCIENCE IN SHORT CHAPTERS.

If the difference of development between the human and canine internal antennae produces all this difference of func¬ tion, what a gulf may there be between our powers of perceiv¬ ing material emanations and those possessed by insects ! If my anatomical hypothesis is correct, some insects have protrud¬ ing nasal organs or out- thrust olfactory nerves as long as all the rest of their bodies. The power of movement of these in all directions afford the means of sensory communication over a corresponding range, instead of being limited merely to the direction of the nostril openings. In some insects, such as the plumed gnat, the antennae do not appear to be thus movable, but this want of mobility is more than compensated by the multitude of branchings of these wonderful organs, whereby they are simultaneously exposed in every direction. This structure is analogous to the fixed but multiplied eyes of insects, which, by seeing all round at once, compensate for the want of that mobility possessed by others that have but a single eyeball mounted on a flexible and mobile stalk ; that of the spider, for example.

Such an extension of such a sensory function is equivalent to living in another world of which we have no knowledge and can form no definite conception. We, by our senses of touch and vision, know the shapes and colors of objects, and by our very rudimentary olfactory organs form crude ideas of their chemistry or composition, through the medium of their mate¬ rial emanations ; but the huge exaggeration of this power in the insect should supply him with instinctive perceptive powers of chemical analysis, a direct acquaintance with the inner molecular constitution of matter far clearer and deeper than we are able to obtain by all the refinements of laboratory analyses or the hypothetical formulating of molecular mathe¬ maticians. Add this to the other world of sensations produci¬ ble by the vibratory movements of matter lying between those perceptible by our organs of hearing and vision, then strain your imagination to its cracking point, and you will still fail to picture the wonderland in which the smallest of our fellow-creatures may be living, moving, and having their being.

Chapter II. Concert-room Acoustics

The acoustics of public buildings are now occupying con¬ siderable attention in London. The vast audiences which any kind of sensational performance in the huge metropolis is capable of attracting, is forcing the subject upon all who cater for public amusement or instruction. There was probably no building in London, or anywhere else, more utterly unfit for musical performances than the Crystal Palace in its original condition ; but, nevertheless, the Handel Festival of last week was a great success. I attended the first of these immense gatherings, and this last ; but nothing of the kind interme¬ diate, and, therefore, am the better able to make comparisons.

My recollections of the first were so very unsatisfactory that I gladly evaded the grand rehearsal of Friday week, and went to the “ Messiah” on Monday with an astronomical treatise in my pocket, in order that my time should not be altogether wasted. Being seated at the further end of the transept, in a gallery above the level of the general ridge-and-furrow roof of the nave, the plump little Birmingham tenor, who rose to sing the first solo, appeared, under the combined optical conditions of distance and vertical foreshortening, like a chubby cheesemite viewed through a binocular microscope. Taking it for granted that his message of comfort could not possibly reach my ear, I determined to anticipate the exhortation by settling down for a comfortable reading of a chapter or two, but was surprised to find I could hear every note, both of recitative and air.

It thus became obvious that the alterations that have gradu¬ ally grown since the time when Clara Novello’s voice was the only one that could be heard across the transept are worthy of study ; that the advertised success of the “ velarium” is something more than mere puffery. I accordingly used my eyes as well as my ears, and made a few notes which may be interesting to musical and architectural, as well as to scientific readers.

Sound, like light, heat, and all other radiations, loses its

SCIENCE IN SHORT CHARTERS.

intensity as it is outwardly dispersed, is enfeebled in the ratio of the squares of distance ; thus at twenty feet from the singer the loudness of the sound is one fourth of that at ten feet, at thirty feet one ninth, at forty feet one sixteenth, at fifty feet aie twenty-fifth, and so on ; that is, supposing the singer or *ther source of sound is surrounded on all sides by free, open, and still air.

But this condition is never fulfilled in practice, excepting, rhaps, by Simeon Stylites when he preached to the multitude oin the top of his column. If Mr. Vernon Rigby had stood a the top of one of his native South Straff or dshire chimney - shafts, of the same height above the ground as the Upper Press Ballery of the Crystal Palace is above the front of the orches¬ tra, and I had stood on the open ground at the same distance away and below him, his solo of “ Comfort ye, my People’’ would have been utterly inaudible.

What, then, is the reason of this great difference of effect at equal distances ? If we can answer this question, we shall know something about the acoustics of concert rooms.

The uninitiated reader will at once begin by saying that “ sound rises.” This is almost universally believed, and yet, it is a great mistake, as commonly understood. Sound radiates equally in every direction — downward, upward, north, south, east, or west, unless some special directive agency is used. The directive agency commonly used is a reflecting or rever¬ berating surface.

Thus the voice of the singer travels forward more abundantly than backward, because he uses the roof, and, to some extent, the walls and floor of his mouth, as a sound reflector. The roof of his mouth being made of concave plates of bone with a thin velarium of integument stretched tightly over them, sup¬ plies a model sound reflector ; and I strongly recommend every architect who has to build a concert or lecture room, or theatre, to study the roof of his own mouth, and imitate it as nearly as he can in the roof of his building.

The great Italian singing masters of the old school, who, like the father of Persiani, could manufacture a great voice out of average raw material, studied the physiology of the vocal organs, and one of their first instructions to their pupils was that they should sing against the roof of the mouth, then throw the head back and open the mouth, so that the sound should reverberate forward, clear of the teeth and lips. For the first year or two the pupil had to sing only “ la, la,” for

COHCERT-ROOM ACOUSTtCS.

several hours per day, until the faculty of doing this effectu¬ ally and habitually was acquired.

The popular notion that sound rises has probably originated from the fact that in all our common experience the sounds are produced near to some kind of floor, which reflects the sound upward, and thus adds the reflected sound to that which is directly transmitted, and thereby the general result is materi¬ ally augmented.

But if we would economize sound most effectively, we must have not only a reflecting floor, but also a reflecting roof and reflecting walls on all sides of the concert room. These are the conditions that were wanting in the original structure of the Crystal Palace transept, for then the sound of the singer’s voice could travel upward to that lofty arch and sidewise in all directions, almost as freely as in the open air.

This defect has been remedied to a very great extent by the velarium stretched across from the springing of the great arch of glass and iron, and forming a ceiling to the concert room part of the building. Beside this, a wall of drapery is stretched across each side of the transept, and the orchestra has its special walls, roof, and back. There are other minor arrangements for effecting lateral reverberation ; that is, for returning the sound into the auditorium proper instead of allowing it to wander feebly throughout the building.

The general result of these arrangements is to render that portion of the building in which the reserved seats are placed a really luxurious and efficient concert room, of magnificent proportions ; but, very unfortunately and inevitably, these conditions, which are so favorable for the happy eight or nine thousand who can afford reserved seats, render the position of the other half-dozen thousand outsiders more disappointing and vexatious than ever. For my own part I would rather spend a holiday afternoon in the mild atmosphere and the quiet, soothing gloom of a coal-pit than be teased and irritated by a strained listening to the indefinite roar of a grand choir, and the occasional dying vibrations of Sims Reeves’ “top A.”

I have in the above advocated reverberation as a remedy for diffusion of sound. This may, perhaps, appear rather startling to some musicians who have a well-founded dread of echoes, and who read the words echo and reverberation as synonymous. This requires a little explanation. As light is transmitted, reflected, and absorbed in the same manner as sound, and as

SCIENCE ix SHORT CHAPTERS.

light is visible — or rather, renders objects visible — I will illus¬ trate my meaning by means of light.

Let us suppose three apartments of equal size and same shape, one having its walls covered with mirrors, the second with white paper, and the third with black woollen cloth, and all lighted with central chandeliers of equal brilliancy. The first and second will be much lighter than the third, but they will be illuminated very differently.

In the first, there will be a repetition of chandeliers in the mirrored walls, each wall definitely reflecting the image of each particular light. In the second room there will be reflection also, and economy of light, but no reflection of definite images ; the apartment will appear to be filled with a general and welldiffused luminosity, rendering every object distinctly visible, and there will be no deep shadows anywhere.

In scientific language, we shall have, in the first room, regu¬ lar reflection ; in the second, scattering reflection ; in the third room we should have comparative gloom, owing to the absorp¬ tion of the light by the black cloth.

We may easily suppose the parallels of these in the case of sound. If the velarium and side walls of the transept and orchestra were made of sheet iron, or smooth, bare, unbroken vibrating wooden boards, we should have a certain amount of regular reflection of sound or echo. Just as we should see the particular lights of the chandelier reflected in the first room, so • should we hear the particular notes of the singer or player echoed by such regularly vibrating walls and ceiling.