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materials, is so vast that as contraction | matter so small that it could not be brings the materials, on the whole, again subdivided into half. No doubt, somewhat nearer together, the poten- so far. as most ordinary experience tial energy thus surrendered is trans- goes, this statement may be unquesformed into a supply of heat quite tionable. It is quite true that we do adequate to compensate for the losses not often reduce matter to fragments arising from the radiation by which the so small that each of them shall be contraction was produced. The stu- iususceptible of further conceivable dent who admits - and who is there division. But, to illustrate the patural that does not admit ? — the doctrine of principle now under consideration, let the conservation of energy knows that us take the example of a body which is: in this argument he is on thoroughly itself composed of but a single element. reliable ground. At the same time the Think, for instance, of a diamond, argument does not actually offer any which is, as we all know, a portion of very clear conception, or indeed any crystallized carbon. It is true that the conception at all, of the precise modus reduction of diamonds to powder is a operandi by which, as the active poten- laborious process. Still, diamond dust tial energy vanishes, its equivalent in bas to be produced in the finishing of available heat appears. I have always the rough stone, and this element will felt that this was the unsatisfactory serve the purpose of our present argupart of an otherwise perfect theory. ment better than a substance of a comIt was, therefore, with much interest posite nature. Each particle of the that I became acquainted a short time diamond dust is, of course, as much a ago with a development of the molec- particle of carbon as was the original ular theory of gases which afforded crystal. We may, however, suppose precisely what seemed wanted to make that by a repetition of the process a every link in the chain of the great reduction of the diamond dust to pow, argument distinctly' perceptible. I der still liner is accomplished. The make no doubt that the notions which grains thus obtained may have become have occurred to me on this subject so minute that they have ceased to be must have presented themselves to visible to the unaided eye, and require others also. I have, however, not read a microscope to render them perceptiin print or heard in conversation any ble ; but even after this comminution use made of the illustration that I am each of these particles is still going to set forth. I feel, therefore, veritable diamond. It possesses the confident that even if it be known at properties, optical, chemical, and meall, it is certainly not generally known chanical, of the originalgem, from among the large and ever-increasing which it differs merely in the attribute circle of readers to whom the great of size. Even when the disintegration questions of physics are of interest. has been carried to such a point that

The division of matter into the three each individual particle can be only forms of solids, liquids, and gases las just perceived by the keenest power of acquired in these days a special sig- the most powerful microscope, there is nificance now that the constitution of still no indication that the particles matter is becoming in some degree un- cease to possess the characteristics of derstood. First let it be noted that, the original body. These facts being though matter is capable of subdi- undoubted, it was perhaps not unnatvision to a certain extent, yet that ural to suppose that the reduction there is a limit beyond which subdi- could be carried on indefinitely, and vision could not be carried. This that even if the smallest fragment of statement touches upon the ancient diamond which could be seen in a powcontroversy as to the infinite divisi- crful microscope were reduced to a bility of matter. Even still we can millionth part, and each of those to a find the statement in some of our old million more, yet that the ultimate partextbooks that there is no particle of ticles thus reached would be diamonds



still. Now, however, we know that of any composite body into coustituent that is not the case. The smallest par- atoms of other elements is not alone ticle visible under a microscope might possible, but is incessantly taking indeed be crushed into a thousand place. parts, and each one of those parts, The first step in our knowledge of though wholly inappreciable to our the constitution of matter has been sense of touch or vision, would never taken when we have come to recoguize theless be a genuine diamond. .If, that every body is composed of a multihowever, the subdivision be carried tude of extremely, but not infinitely, on until the particles produced: are, small molecules. The next point reroughly speaking, one-millionthi part of lates to the condition in which these the bulk of the smallest objects which molecules are found. At first it might could be seen in the microscope, we be thought that in a solid, at all events, then approach the limits of partition of the little particles must be clustered which the diamond would be suscepti- together in a compact mass. . If..we ble. We now know that there is an depended merely od: sensible evidence atom of diamond so small, that it must it would seem that a lump of iron, if refuse to undergo any further division. constituted from molecules at all, must This ultimate atom, be it observed, is be simply a cohering mass of particles, not an infinitely small quantity. It has just as a multitude of particles of sand definite dimensions ; it possesses a def- unite to form a lump of sandstone.

; inite weight. Allsuch diamond atoms But the truth is far more wonderful are precisely alike in weight, and prob- than such a belief would imply. Were ably in other characteristics. It might the sensibility of our eyes so greatly inbe thought that if this atom has finite creased as to make them a few million dimensions, it is, at all events, conceiv- times more powerful than our present able that it should admit of further organs, then, indeed, the display of the subdivision. In a certain sense this texture of solid matter would be an is, no doubt, the case. The diamond astonishing revelation. It would be atom is made up of parts and, being so seen that the diamond atoms, which, made, it is, of course, conceivable that when aggregated in sufficient myriads, those parts could be separated. The form the perfect gem, were each in a important point to notice is, that no condition of rapid movement of the means known to us could produce this most complex description ; each moleseparation, while it is perfectly certain cule would be seen swinging to and fro that if the decomposition of the atom with the utmost violence among the of diamond into distinct parts could be neighboring molecules. It would be effected, those parts would not be dia- seen quivering all over under the influmonds at all, nor anything in the leastence of the shocks which it would reresembling diamonds.

ceive from the vehement encounters What we have said as regards the with other molecules which occur milelement carbon may be extended to lions of times in each second. Such every other elementary

elementary substance, would be the minute anatomy of the Sulphur is familiarly known in a form diamond. The well-known properties of extreme subdivision, and each little of such gems seem, at first sight, particle of sulphur could be further wholly at variance with the curious comminuted to a certain point beyond structure we have assigned to them. which any further partition would be Surely, it may be said that the hardimpossible. So, too, any composite ness and the impenetrability, so characbody, such, for example, as. a lump of teristic of the diamond refute at once sugar, admits of being decomposed into the supposition that it is no more, thau molecules so small that any further a cluster of rapidly moving particles. separation would be impossible if the But the natural philosopher now knows molecule were still to remain sugar. that his explanation of the qualities of No doubt, a separation of the molecule the diamond holds the field against all other explanations. The well-known | vibration. It is impossible that such impenetrability of the diamond seems vibrations could be produced were it to arise from the fact that when you not that there is in the irou a soinetry to press a steel point into the stone thing which vibrates in such a manyou fail to do so because the rapidly ner as to communicate the necessary moving molecules of the gem batter pulses to the ether. It therefore folthe end of the steel point with such lows that in the texture of the solid extraordinary vehemence that they re- iron there must be some molecular fuse to allow it to penetrate or even to movement, timed in such a way as to mark the crystallized surface. When impart to the ether the actual vibrayou cut glass with a diamond it is quite tions which we find it to possess. The true that the edge, which seems so argument in this case may be illustrated intensely hard, is really composed of by the analogous phenomena presented rapidly moving atoms. But the glass in the case of sound. As we listen to which is submitted to the operation is the notes of a violin, what we actually also merely a mass of moving mole- perceive are vibrations communicated cules, and what seems to happen is, through the air to the auditory apparathat, as the diamond is pressed for- lus. We can trace these aerial vibraward, ils several particles, by their tions back to their source, and we find superior vigor, drive the little particles they originate from the quivering of of glass out of the way. We do not the violin under the influence of the see the actual details of the myriad en- bow of the performer. Were it not for counters in which the diamond atoms these vibrations of the instrument the are victorious over the glassy mole- aerial vibrations would not be procules ; we only discern the broad result duced, and the corresponding sounds that the diamond has done its work, would not be heard. Far more delicate and that the glass has been cut.

than the atmospheric waves of sound It may well be asked how we know are the ethereal waves corresponding to that matter is constituted of molecules light or to heat, but none the less must in intensely rapid movement. The these latter also originate from the instatement seems at the first glance to pulse of some vibrating mass. It is be so utterly at variance with our ordi- thus apparent that a hot piece of iron, pary experience that we demand, and however still it may seem, must be anrightly demand, some convincing proof imated by an excessively rapid molecon the matter. There are many argu- ular movement. Nor is the validity of ments by which the required demon- this conclusion impaired even if the stration can be forthcoming. The one iron be at ordinary temperature. We which I shall give is not perhaps the know that a body whicl no lotter most conclusive, but it has the advan- than the surrounding bodies is still intage of being one of the simplest and cessantly radiating heat to them and the most readily intelligible.

receiving heat from them in return. Let us see if we cannot prove at Thus we are led to the conviction that once that the molecules in, let us say, a a piece of iron, whatever be its tempiece of iron must be in movement. perature, must consist of atoms in a Suppose that the iron is warmed so state of lively movement. The iniporthat it radiates heat to a perceptible tant conclusion thus drawn with regard extent. We kuow that the heat which, to iron may be equally stated with rein this case, affects our nerves has been spect to every other solid, or, indeed, transmitted from its origin by ethereal every other body, whether solid, liquid, undulations. Those undulations have, or gaseous. All matter of every deundoubtedly, been set in motion by the scription is not only known to be comiron, and yet the parts of the metal posed of molecules, but it is also now seem quite motiouless relatively to each certaiu that those molecules are incesother, notwithstanding that they pos- santly performing movements of a very sess the power of sciting the ether into 'complex type.

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A closer study of this subject will be | what usually happens is that the two necessary for our present purpose, and impinging molecules make a very close it will be convenient to examine watter approach ; then each of them so vehein that state in which it is exhibited in mently attracts the other as to make it its very simplest type from the molecu- swerve out of its course and start it off lar point of view. This condition is along a path, inclined, it may be, even not presented, as might at first be sup- at a right angle to that which it previ.. posed, when the matter is solid, like a ously pursued. The molecules in a gas diamond, or like a piece of iron. Even at ordinary pressures are so contiguous in a liquid the complexity of molecu- that these encounters take place inceslar constitution, though somewhat less santly; in fact, we are able to show than in the case of a solid, is still that each individual molecule will probpotably greater than in matter which ably experience such adventures some has the gaseous form. The air that we millions of times in the course of each breathe is matter almost of the most second. We are able to calculate the simple kind, so far as molecular consti- average velocity with which the sevtution is concerned. It should, how-eral molecules move when the gas has ever, be noted that, as air consists of a a certain temperature. We know how mixture, it would be better for our to determine the average length of the purpose to think of a gas isolated from free path which each molecule traverses any other element. Let us take the in the interval between two consecutive case of oxygen, the most important encounters. We are able to trace how constituent of our atmosphere.

all these circumstances would vary if, Like every other element, oxygen is instead of oxygen gas, we took nitrocomposed of molecules, and those mol-gen, or hydrogen, or any other body in ecules are in a state of rapid motion. the same molecular state.

in It inight be expected that the affinity fact, characteristic of every gas that by which the different molecules were each molecule wanders freely, subject allied in the case of a gas should be only to those incessant encounters with of the simplest nature, and this is other similar wanderers by which its indeed found to be the case. Not- path is so frequently disturbed. If withstanding that oxygen is an invis-two gases be placed in the same vessel, ible body, and notwithstanding that the one being laid over the other, it will molecules are so excessively minute presently be found that the two gases as to be severally quite inappreciable begin to blend ; ere long one gas will to our senses, yet we have been able have diffused uniformly through the to learn a great deal with regard to the other, so that the two will have become constitution of the molecules of this a perfect mixture just as the oxygen gas. The mental eye of the philoso- and nitrogen have done in our own pher shows him that, though the oxy- atmosphere. The molecular theory of gen with which a jar is filled appears to gases explains at once the actual charbe perfectly quiescent, yet that quies- acter of the operation by which diffucence has there no real existence. He sion is effected. Across the boundary knows that oxygen consists of myriads which initially separates the two gases of molecules identical in weight and in certain molecules are projected from other features, and darting about one either side, and this process of interamong the other with velocities which change goes on until the molecules bevary perhaps between those of express come uniformly distributed throughout. trains and those of rifle bullets. He There is, indeed, nothing more resees that each little molecule hurries markable than the fact that information along quite freely for a while until it so copious and so recondite can be happens to encounter some other mole- obtained in a region which lies altocule equally bent on its journey, and gether beyond the direct testimony of then a collision takes place. Perhaps the senses, Just as the astronomer it would be more correct to say that staggers our powers of conception by

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the description of appalling distances the little particle will swing clear away and stupendous periods of time, and from the influence of the other molerelies with confidence on the evidence cules with which it had been associated. which convinces him of the reality of When this takes place in the case of a his statements, so the physicist avails sufficient number of molecules, they himself of a like potent method of re- dart freely from the surface of the search to study distances so minute liquid, thus producing the effect which and times so brief that the imagination in our ordinary language we describe utterly fails to realize them.

as giving off steam. If, therefore, a In the case of a liquid, the freedom volume of gas be heated, the velocities enjoyed by the molecules is consider- with which its molecules are animated ably more restricted than in the case of will be in geveral increased. As the a gas. It would seem that in the molecular velocities throughout the exdenser fluid there can be no intervals tent of the gas are, on the whole, of uudisturbed travel permitted to a augmented, it is quite plain that the molecule ; it is almost incessantly in a intensities of the shocks experienced state of encounter with some other by the molecules in their several ensimilar object. When a molecule in a counters will be also accentuated. The liquid breaks away from its association more rapidly moving particles will with one group, it is only because it strike each against the other with inhas entered into alliance with another. creased violence, and the contemplation As, however, two liquids · will very of this single fact leads us close to one frequently blend if so placed that dif- of nature's greatest secrets. fusion be possible, we have a proof Let us think of the abounding heat that, though the transference of a par- which is dispensed to us from the sun. ticular molecule through the liquid may That heat comes, as we know, in the be comparatively slow, yet it will grad-form of undulations imparted to the ually exchange association with one ether by the beated matter in the sun, group for association with another, and and transmitted thence across space for may in this way travel throughout any the benefit of the earth and its inhabdistance to which the liquid extends. itants. I have already explained that

In the case of a solid there is still these vibrations in the ether njust take further limitation imposed on the mo- their rise from molecular movements, bility of each separate molecule. It is and it is important to notice that the now no longer permitted to make ex- character of the vibrations in the ether cursions throughout the entire volume enable us to learn to some extent the of the body. Each molecule is in rapid precise description of molecular movemotion it is true, but those movements ments which alone would be competent are confined to gyrations within mi- to produce the particular vibrations nutely prescribed limits. Two solids corresponding to radiant heat. At first placed in contact do not generally dif- it might be thought that it was the fuse one into the other, the incapacity rapid movements of translation of the for diffusion being the direct conse- molecules themselves, as entire if exquence of the inferior degree of mobil-tremely minute bodies, which caused ity possessed by the molecules in this the ethereal vibration, but this is not condition of matter.

We must carefully observe that It is known that the immediate effect there is another kind of molecular moof the application of heat is to increase tion besides that which the molecule the velocities with which the molecules possesses as a whole. We have hith

Apply heat, for instance, to the erto been occupied only with the movewater in a kettle ; the moving molecules ments of each molecule as a little of water are thereby stimulated to even projectile pursuing its zigzag course, greater activity and it will occasionally each turn of the zigzag being the result happen that the velocity thus acquired of an encounter with some similar by a molecule becomes so great that molecule belonging to the same me



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