^{page 29 note *} See Treatise on Natural Philosophy by Thomson and Tait (new ed.), vol. i. part i. §§ 300–306.

^{page 30 note *} The part within brackets has been written by a mathematician, who advised me that it was better put in this way than in the way in which I originally put it. It is, at any rate, far more concise.

^{page 33 note *} After the condensation, or shell, was reduced to a single particle in thickness, the motion still continuing, as it must, the particles to which the motion has been transmitted can no longer be neighbours, but gradually get separated, till at last they may be any distance apart. So that the motions which generate tha pressure in the ether, and in which contiguous particles are engaged, may be generated in opposite quarters of the universe. And these motions can no longer be wave motions, for the latter consist in a simultaneous motion of all the particles, at the same distance from the point of disturbance of the medium, in the same direction; but the pressure motions being generated at all distances, in opposite directions, act on each particle independently, and thus subject the medium to simultaneous and contrary motions, and which generate the intense pressure.

^{page 34 note *} It goes without saying that I conceive this pressure as the source of all the so-called “Forces.”

^{page 35 note *} It has been objected to the constitution of the ether herein set forth that it would be nothing more nor less than a gas. This objection I quote from Stallo's Concepts and Theories of Modern Physics, p. 97: —”The negative evidence here adduced against the supposition of an atomic or molecular constitution of the light-bearing medium is re-enforced by positive evidence derived from a branch of the atomic theory itself—the modern science of thermo-dynatnics. Maxwell has remarked, with obvious truth, that such a medium (whose atoms or molecules are supposed to penetrate the intermolecular spaces of ordinary substances) would be nothing more nor less than a gas, though a gas of great tenuity, and that every so-called vacuum would in fact be full of this rare gas at the observed temperature and at the -enormous pressure which the aether, in view of the functions assigned to it by the undulatory theories, must be assumed to exert. Such a gas, therefore, must have a correspondingly enormous specific heat, equal to that of any other gas at the same temperature and pressure, so that the specific heat of every vacuum would be incomparably greater than that of the same space filled with any other known gas.” I submit, it will be found further on that this objection is met by the difference which this theory assigns to the constitution of the ethereal atom from that of the material atom. The ethereal atom is a simple, structureless body, incapable of absorbing or retaining heat, —simply passing it on as received from its neighbours on the one side to its neighbours on the other; but the material atom and molecule are furnished ‘with springs, so to speak, and upon which motion can be impressed so as to be retained by them for some time, until by their vibrations they gradually communicate it to the ethereal medium.

^{page 39 note *} It will, no doubt, be observed that this is a position of unstable equilibrium, which the slightest disturbance would overthrow. How, then, are we to save the situation ? It is saved already. For, as pointed out above, the particles would be more bombarded on their fronts than on their rears, so that although, by falling in towards the centre, they would regain their former speed, their orbits, if ever they were circular, would never be so again, but always elliptical, and no bubble could ever be in so expanded a state as it would be possible for it to be if this excess of bombardment on the fronts of the particles over the rears did not exist. In short, owing to this excess of bombardment on their fronts, no bubble could ever expand to the stage of unstable equilibrium.

^{page 40 note *} Or, to put it in another way, as in twice the distance of a circular orbit there is four times the curvature, twice the pressure for the same time produces twice the velocity = four times the kinetic energy, which would produce four times the curvature in the paths of the particles.

^{page 44 note *} It must be borne in mind that it is only the radiations causing pressure which would be effective here—not the sun's waves. These would only be effective after dwindling to their lowest form.

^{page 48 note *} I am anxious that this point should be thoroughly grasped; so, at the risk of some repetition, I will go over it again in other words. Well, then, it seems clear that, granted the radiations producing pressure equal from all directions, if a body moved in any direction it must move against them, and if they have any influence on.it they must, apparently, retard it, for the motion of the body added to that of the radiations opposing it strengthens those radiations, and weakens those following the body up behind, so that, apparently, nothing can save it from retardation. But owing to the constitution of my theoretical atoms no retardation, so far as the strengthening of the radiation is concerned, could take place, for the increased pressure on the front of each atom would tend to increase the motion of the particles of which it is composed, and which increase would be neutralised by the decrease of pressure on the rear due to the diminished radiations from this direction, so that, on the whole, the mean motion of the particles of each atom would not be altered. This clears the way so far as the radiations are concerned, provided they are equal from every direction; if they are not, it seems clear that the body must drift in the direction from which the diminished radiation reaches it, and with a velocity proportional to that diminished radiation.

^{page 49 note *} I doubly emphasise this point,, for it would be as though the sun existed there and nowhere else.

^{page 50 note *} The spheres would begin to “attract” one another when they were some little distance apart (I use the word “attract” as having a well-established meaning); in fact, this process would begin when the film of ether between them became so thin as not to be able to carry the full pressure.

^{page 52 note *} Heat, a Mode of Motion, p. 346, 6th ed., 1880.Google Scholar

^{page 53 note *} It is clear that absorption must be brought about in the inverse way to radiation. Radiation means a crowding together of the ethereal particles by the energy resident in the molecule; absorption is brought about by the energy iu the wave; the wave strikes the atom on one side only, the opposite side being, at least, partly shielded by its partner in the molecule, and in this way motion towards its partner is produced.

^{page 58 note *} J. P. Cooke, “The New Chemistry,” pp. 246, 247.

^{page 61 note *} If I have made any blunders in my chemistry I hope I may be excused, as I gave fair warning when entering on the subject that I knew very little about it. But to the chemists I should like to say that I have given them an atom, with its great potentialities, and shown them its hooks, clamps, or bonds; and I do think that it is for them, with the knowledge of the facts at their fingerends, to clamp the atoms together in the way which best suits the facts; and sure am I that if they give the subject a little of the thought which I have given, they will soon be able to string all the facts together into one perfect whole. My text-books of chemistry, I find, are somewhat out of date. Since writing the above I have been given to understand that valency does not always vary by two steps at a time. If this be so, there must be some peculiarity in the circumstances attending the departure from the rule, or the departure, one would think, would have been discovered long ago. Possibly, though, this very departure, when the circumstances attending it are thoroughly inquired into, may serve to confirm my theory.