DIVISIBILITY OF MATTER.

xxxi the theories that have been proposed for the resolution of this question from the time of Leucippus, Democritus, and the great philosopher of Stagyra, to that of our own era. Beautiful and ingenious as many of these hypotheses are, they often fail to bear the rigid investigation of truth, and too frequently are found to have their superstructure based on no better foundation than the brilliant and fertile imaginations of those, who introduced them to the world.

If we take a mass of any form of matter and reduce it to the finest impalpable powder by any mechanical means, it must not be considered that this state of comminution, however fine and minute, has put us in possession of atoms of matter in their minutest state of division; for, on examining with a lens a particle of the powder thus obtained, we find it to closely resemble the mass from which we obtained it, and of which it is in every respect a miniature likeness. So that it is probable that had we cutting instruments sufficiently delicate, and visual organs sufficiently microscopic, we might continue dividing this particle into numerous smaller portions. This circumstance has been very lately proved, by the microscopic labours of Ehrenberg, to be strictly and literally correct, and to hold good where it was least expected. This philosopher, among other observations, has shown, that chalk in its minutest state of comminution, after it has been exposed to the action of a mill, and then the finest portions separated by the operation of elutriation, still under a good microscope appears to be composed of transparent rhomboids, with angles as perfect as in the finest specimen of calcareous spar. Here arises the first question in this stage of our enquiry; for, admitting that we are able to continue our division of the particles, we should naturally ask, what would be the limit to this division?could it be carried on to infinity, or is there a point at which it must stop? Some philosophers, there are, who consider that this state of division may be carried on to infinity, and, If this be the consequently, that matter is divisible for ever.

case, there can be no such thing as an atom; certainly not, if its strict definition be adhered to. What then can a mass of matter be constructed of? Can it be supposed to consist of an aggregation of infinitely divisible particles? If so, of what are these particles themselves composed, if their division can be continued for ever? So that we are almost compelled to regard the division of matter as limited; for, if we do not admit this finite division of masses, we can have no idea, or capability of appreciating its compound particles. To appreciate numbers, we must be acquainted with the number of units they contain; to appreciate a mass, we must admit the existence of a finite division into particles or atoms. Again, matter no one can suppose to be else than mortal; it is no attribute of spiritual or immortal beings; then, if we admit that matter is essentially connected with beings which are limited in duration of existence, does it not appear to involve an absurdity to suppose that the constituents of that which is limited in existence are infinite in number? "It would be as easy to believe that a moment of time may be lengthened into an infinity of ages, as to suppose that matter is infinitely divisible. Nothing can be more revolting to reason than eternal time; infinite divisibility is not less absurd;" although it must be acknowledged a most difficult task to adduce a precise refutation of all the mathematical sophistry and subtleties concerning infinite divisibility, with which the question has been loaded. The mind is unable to continue the contemplation of this subject; it becomes bewildered in the mazes of the question, and seeks for relief from the obscurity enveloping the labyrinths, which the thinking powers are unable to penetrate, in the consideration of those deductions countenanced by reasoning, experiment, and experience.

We have next to enquire, by what force the particles of matter, which we have obtained from the mechanical comminution of a mass, were held together previous to their forcible separation. Some force must exist for this purpose,

ATTRACTION AND REPULSION OF ATOMS. xxxiii

otherwise no such thing as an aggregation of atoms forming a mass could ensue; for we can consider particles of dead matter only as absolutely inert, and, therefore, of themselves could not oppose that obstacle to their forcible separation which is presented by every solid material mass; and this reasoning brings us to notice a most energetic force presiding over the internal constitution of bodies. This force is attraction; and by its aid one particle of matter is held in close approximation to a second, and thus causes the formation of a mass. Reasoning from known facts, teaches us that this attractive force must be considerable, otherwise it would be impossible to account for the difficulty we experience in attempting to divide a mass of any substance; it also teaches us that the sphere of this attraction is limited to distances quite insensible to the eye, even when assisted by the best microscopes. For, having once reduced a mass to powder, the minute particles composing this, ought again to unite on collecting them into a heap on a piece of paper; for the particles appear to the naked eye to touch each other, and therefore to afford every opportunity for the exertion of a mutual attractive force to reconstruct the mass we have disintegrated. But we know that this attraction does not become apparent; the particles of matter do not fly together, unite, and form a mass; therefore, it must follow that the sphere or extent of this attractive force is extremely limited.

The attraction between two particles cannot be infinite, for, if so, no earthly power could effect their separation; hence there must exist some power or force modifying this attraction, acting consequently in opposition to it. For it appears evident from the results of experiment that, although two particles have so powerful an attraction for one another, as soon as they are brought within the sphere of each other's attraction, that they unite and constitute one mass; yet, that if it be attempted to bring them into absolute contact, a most powerful resistance is opposed to our attempts, and the task

becomes impossible, demonstrating the existence of a repulsive force between individual particles as well as between masses of matter. Admitting the existence of these two forces, attraction and repulsion, acting on the particles of matter, let us investigate the attributes of the latter in its minutest physical state of division, rejecting entirely the hypotheses I have hinted at, which consider matter either as infinitely divisible or as entirely non-existed; for theories of this kind must be regarded as purely metaphysical, and, therefore, quite distinct from our present investigations. Indeed, by reasoning on matter in the abstract, we gain comparatively little; it is by studying it in relation to other masses, and the external world, that we gain anything practically useful.

It has been fairly deduced from accurate reasoning and observation, that all ultimate physical, indivisible atoms, possess the attributes of impenetrability, hardness, and figure. What their form really is, it is impossible to say: philosophers have exhausted the fertility of their imaginations on this subject; the ancients supposed them to be possessed of various forms; most modern writers have assumed them to be spherical; and, certainly, in reasoning on their properties and attributes, this form is found most available; a late Italian author has attempted to prove them to be pyramidal. To enter into these speculations would however be useless and unprofitable, as it is self-evident that no direct proof can be brought to bear upon the subject. If the component atoms of any form of matter be placed sufficiently near to each other, by the action of a mutually attractive force, we have a solid produced; if a repulsive energy be now exerted, the atoms fly asunder, and we have a soft solid, or liquid; and this, upon a still further application of repulsion, becomes converted into a gas, or vapour, from the more distant separation of its component atoms. As an example of these different states, let us take ice. This is a well known solid of considerable hardness, justifying the idea that its atoms

VIBRATIONS OF PONDERABLE MATTER.

XXXV

are very closely approximated to each other; on applying a gentle heat, these atoms separate and a fluid, water, is produced; a still greater degree of heat causes a further separation of atoms, and a vapour, steam, is generated in this state a given number of atoms occupy a space 1728 times greater than they did when constituting fluid water. Many other forms of matter may be made to assume the several states of solid, fluid, and gas. In the case of carbonic acid this is beautifully demonstrated, an invisible gas having, under powerful pressure, its molecules so approximated that a fluid is formed; and then, under the influence of intense cold, a still further approximation ensues, and a white solid, resembling snow, is produced. All these several states of matter will fall under our observation in the investigation of the sciences of Statics, Dynamics, Hydrostatics, and Pneumatics. (Chap. I—VIII.)

Masses of matter constituted in the manner thus described are said to be brittle, if the attraction between their atoms are so slight as to be overcome by a slight blow;-to be tenacious, if this attraction is so intense that it cannot be readily overcome;-and to be elastic, if upon the application of force, their atoms allow of partial separation, and rapidly reunite on the removal of pressure. If, for example, a glass vessel be lightly struck, its atoms momentarily separate, then rapidly return to their normal state, by a series of isochronous oscillations, their movements are communicated to the air, an eminently elastic body; alternate dilations and contractions ensue in those layers of air nearest the agitated body, these become gradually extended into the great mass of atmosphere, like the waves formed on the surface of a lake by the falling in of drops of rain, and gradually extend in rapidly dilating circles until they vanish from the eye of the observer. When these vibratory movements occur with sufficient rapidity, they excite in the organs of hearing that sensation termed a sound, and on the quickness or slowness of their succession depend all the varieties of grave and