The idea that the ether can be pumped out of a tube of any kind, along with the air or gas that has been shut up with it therein, will very probably be declared to be absurd, by reference to Dr. Crookes's experiments with his Radiometer, and investigations into the nature of radiant matter; but when duly considered his work seems to confirm it, and our reasonings in support of it, in a very convincing manner. Radiant heat, or light, is shown, no doubt, to penetrate into an exhausted bulb and to cause a radiometer to revolve, but we have to consider what is the state of exhaustion at which its force is shown to be greatest, and why that force decreases rapidly when the exhaustion is progressively increased beyond a certain point; for a certain amount of exhaustion is required first of all to diminish the resistance of the air or gas to the vanes of the radiometer, before the radiant heat gathers force enough to make them revolve at all. Its greatest power to produce revolution is shown to be when the exhaustion is at from 30 to 60 millionths of an atmosphere, according to the gas or medium in the bulb—see "Engineering," Vol. XXV., page 155—and decreases from that point, often rapidly, as the exhaustion is increased, till at last it ceases altogether. Everybody who has taken any interest in the subject, knows that Dr. Crookes has exhausted radiometers to such a degree that they could not be influenced by the radiation of a candle placed a few inches from the bulb. We are not told at what degree of exhaustion this took place, nor at what degree repulsion, by radiation of heat, is supposed to have ceased altogether, but that does not matter, even though it should only cease when the vacuum comes to be absolute—most probably a stage to which it is impossible to attain. What concerns us is the fact that repulsion by radiation does reach a maximum at a certain degree of exhaustion, and then falls off as the exhaustion is increased; and what we have got to consider is what is the cause of the falling off. We are told it is caused by the attenuation of the matter, gaseous or material, contained in the bulb, and we are satisfied with the explanation. But in order to be thoroughly so, we must insist on believing that it is part of the whole of the matter that has been operated on; not only of the gas and other matter to the exclusion of the ether, but of the whole, ether and all. If the ether is left behind intact, it must perform the offices it was created for by the imagination of man, or man must discard it altogether. If it ceases to carry light and heat through a vacuum, it is of no more use than we found it to be in the case of electricity, and man is bound to dismiss it as a useless operative, who will strike work for no reason whatever. Some people have supposed the ether to be an absolute non-conductor of electricity, because it does not convey that agent through a vacuum. Will they also declare it to be a non-conductor of light and heat? If they will not, then they—and we presume everyone else—must admit that it can be pumped out of a bulb, in the same way as a gas or any other fluid matter.

Here we are led into another consideration, viz., whether the ether is exhausted from a receiver by pumping alone, or by the help of absorption. In his lecture, "On Radiant Matter," delivered at the British Association, at Sheffield, August 22, 1879, Dr. Crookes said: "By introducing into the tubes appropriate absorbents of residual gas, I can see that the chemical attraction goes on long after the attenuation has reached the best stage for showing the phenomena now under illustration, and I am able by this means to carry the exhaustion to much higher degrees than I get by mere pumping;" and that when working with absorbents: "The highest vacuum I have succeeded in obtaining has been 1/20,000,000th of an atmosphere, a degree which may be better understood if I say that it corresponds to about the hundredth of an inch in a barometer column three miles high." (We quote from "Engineering," Vol. XXVIII., page 188.)

Now, what are we to think? Are we to suppose that the ether was in part removed by the absorbents? We think we are justified in saying that the absorbents had not anything to do with the exhaustion of the ether, because Dr. Crookes used different kinds of absorbents for the different kinds of gases he dealt with, and it is hard to believe that all the media he used were equally effective in absorbing the ether as they were with the gases. On the other hand, if we consider that the pumping was the only agent in removing the ether, we ought to acknowledge that it must have been more effective with regard to it than to the gases before absorption was resorted to with them; or that a stage had been reached at which the pump could not extract any more ether from the bulb. We shall have more to say of this presently. It is a difficult matter to determine, but there is one thing we can see clearly; when the exhaustion of the bulb was raised to 1/20,000,000th of an atmosphere, the density of the ether—of itself—must have been at a lower degree than that. Consequently if we assume its normal density to be 1/5,264,800th of an atmosphere, in terms of the estimate we quoted from "Engineering," it must have been diminished to less than one-fourth of that when the above high vacuum was obtained; because it must have been the density of the residual gas, or matter, and of the ether, added together which amounted to 1/20,000,000th; the same as we have argued with regard to the solar nebula when at 6,600,000,000 and 29,000,000 miles in diameter.

One thing leads to another, and we have again to repeat our question—What is a gas? And all the answers we have been able to get to it hitherto have been far from satisfactory.

A little earlier in the same lecture, referred to a few pages back, Dr. Crookes, after telling us, very elaborately, what would have been the definition of a gas at the beginning of this century, goes on to say:

"Modern research, however, has greatly enlarged and modified our views on the construction of these elastic fluids. Gases are now considered to be composed of an almost infinite number of small particles or molecules, which are constantly moving in every direction with velocities of all conceivable magnitudes. As these molecules are exceedingly numerous, it follows that no molecule can move far in any direction without coming in contact with some other molecule. But if we exhaust the air or gas contained in a close vessel, the number of molecules becomes diminished, and the distance through which any one of them can move without coming in contact with another is increased, the length of the mean free path being inversely proportional to the number of molecules present. The farther this process is carried, the longer becomes the average distance a molecule can travel before entering into collision; or, in other words, the longer its mean free path, the more the physical properties of the gas or air are modified."

Of course, what we have looked upon as Dr. Crookes's definition of a gas, ends with the second sentence of the above quotation, and is far from being sufficiently complete to be satisfactory; but we have continued to quote from the lecture, because it contains matter which demands consideration, and helps very powerfully to support the conclusions we have been arriving at.

Why the definition is not satisfactory, is that it does not tell us what there is in the spaces between the molecules of what is called the gas. If there is room for them to move in every direction there must be spaces between them, and these spaces must either be absolutely empty, or filled with something. If they are supposed to be empty, then the molecules being actually small pellets, like diminutive marbles, or snipe-shot, we immediately begin to think why gravitation does not make them, being ponderable bodies, fall down to the bottom of the bulb; and seeing that, by the definition, they are evidently considered not to do so, we think of what can keep them from falling, and of how they can be pumped out of a bulb or any sort of vessel. If we fill a vessel with marbles, snipe-shot, wheat flour, or dust, and set a pump to work on it, we shall find that we make very little progress in pumping them out of it. At first we might extract a puff or two of flour or dust—marbles or snipe-shot by no means—carried into the pump by any air there might be mixed with them, but that would very soon come to an end; besides, there would be air, gas, something, in the interstices—if any—of the flour or dust to drive them into the pump when a vacuum was formed in it, and the puffs would cease when the air, which would be in exceedingly small quantity, was all extracted. But independently of all this, we have supposed the spaces between the gas pellets or molecules to be absolutely empty, and there would be nothing to push them into the vacuum created in the pump. There is no possibility of pumping marbles, sand, flour, or dust out of a vessel without the assistance of a fluid agent of some kind, water, gas, or air; and even then it would be done with much difficulty.

Let us, then, suppose there is some such agent filling the spaces between the atoms of the gas and think of what it must be. Were we to ask the question we have a strong suspicion the first impulse of many people would be to reply—With gas of course. But this reply could not satisfy us. We should immediately be led to think of that gas also consisting of atoms with vacant spaces between them filled with something—some more gas; and were we to follow up that thought through a sufficient number of stages, it is easy to see that in the end the whole space occupied by any gas would come to be filled up with its own solid atoms, without any empty spaces between them through which they could move; and so rendered quite incapable of pushing each other into a vacuum formed by any pump that might be applied to extract them from any vessel of any kind; or we must suppose that each particle would fly of its own good will into the vacuum made by the pump—as it were on the wings of the morning. But we recall to memory that the wings of the morning do not always carry us to rest, and we see that filling the spaces with gas would only end in choking up the vessel altogether. It might be said: Nobody imagines that the molecules of the gas in the spaces would be sufficient to fill them up altogether; and then we have only to ask, What then would there be in the spaces between the molecules of these successive gases to prevent the whole of them from gravitating to the bottom of the vessel? And to add that there would still be empty spaces left, absolutely empty, that would have nothing in them to help in any way to force the molecules or atoms of any gas or vapour into a vacuum anywhere. It is clear then that a gas, such as Dr. Crookes has described a gas to be, could only end in filling the spaces left between its molecules or atoms. It would be an obstruction to their collisions and bombardments which form an essential part of the description or definition.

We must, therefore, have recourse to something else for filling up the spaces between the molecules of a gas, and the only thing we can lay hold of is our limited liability agent the ether, which we allow to do all we want it to do and nothing more. Vapours of solid or liquid matter would be of no use, for they would only condense into solid or liquid matter; unless always maintained at their temperatures of evaporation or ebullition, and that would at the best be only another form of a gas—nobody would use a liquid to assist in pumping air out of a vessel—and, besides, we should still have to show what keeps their particles apart, what fills the spaces between them, which would force us to appeal to the ether as the only source, just as before. If there are no spaces between the particles there can be no vapours.

If by pumping air out of a close vessel the number of its particles is diminished, and we acknowledge that the ether pervades all space and matter, in a greater or smaller degree, then we must either recognise that a pump is able to separate the particles of the air from the ether which pervades it in the vessel, and extract them alone; or we must acknowledge that along with the particles of the air, the pump extracts a corresponding portion of the ether. Which of these two consequences of the pumping we have to choose cannot for a moment be doubtful. It would be as reasonable to suppose that we could pump the colouring matter out of a pond of muddy water, or the mud itself, and leave the clear water behind, as to suppose that the molecules of air, or of a gas, could be extracted from a close vessel, by a pump, and the ether left behind in it.

We have called attention two or three pages back to the fact that a fluid agent of some kind is required, in order to be able to pump matter of any description out of any kind of vessel. For solid matter a non-elastic fluid will suit, but for gaseous or vaporous bodies an elastic fluid is required; but we have just seen that what have hitherto been considered to be elastic fluids, that is, gases and vapours, have no elasticity whatever of their own, but are undoubtedly and in reality solid matter; and that in order to become elastic fluids they have to be mixed with the ether, or something that has yet to be discovered, invented, or imagined. If, then, until such a body is found we take the ether as a substitute, we have to acknowledge that it must be not only an elastic fluid but a material substance, capable of being compressed and expanded, and heated and cooled; for nobody could conceive clearly the existence of an elastic fluid that is not subject to these conditions. He could not understand how the molecules of a gas could be contracted, expanded, heated and cooled in a vessel, while the elastic fluid which gave them liberty to move or to be moved, remained constantly at one density and temperature. Furthermore, until such a substitute is found, we have to acknowledge that it is the only thing we have any idea of corresponding to a gas as described by Dr. Crookes; that is, a multitude of molecules colliding with and bombarding each other or their prison walls. But even beyond this we can uphold it to be the only real, independent gas there is; because, being an elastic fluid, there is no necessity for there being empty spaces between its molecules, or even having molecules in the common acceptation of the term. We have no reason to think that there are empty spaces between the molecules or particles of indiarubber; and if there are, the ether is the only substance we can properly conceive them to be filled with.

The law of Avogadro is, that "Equal volumes of gases and vapours contain the same numbers of molecules, and consequently that the relative weights of these molecules are proportioned to the densities." Therefore we must always bear in mind that it is the weights, not the volumes, which are equal, and that the volumes may be very different. On this earth of ours, then, we may say with certainty that an atmosphere of gas is composed of a definite number of its special kind of molecules, mixed with a definite quantity of the ether, in such proportion that the sum of their densities shall be equal to the density of the air, at atmospheric pressure at sea level, and at 0° of temperature. Holding this belief, we can see that each molecule, or rather atom, of each gas must have its own amount of displacement to enable it to float in the ether with which it is mixed. This would account in the most satisfactory manner for the diffusion of gases, whereby any molecule, or atom, may float wherever it is driven by collisions with its neighbours, be it above, or below, or on a level with, a molecule of a lighter or heavier gas. Therefore, were it possible to determine with sufficient accuracy the dimensions of the atoms of all gases, perhaps even of a limited number of them, it would be possible to calculate the real density, or specific gravity, of the ether.

We have not forgotten that when, by pumping, the ether was reduced to at least one-fourth of its normal density, its buoyant power would be reduced in the same proportion, nor that, when in a state of rest, the displacement of a molecule, which enabled it to float in the ether, would not be sufficient to make it float at one-fourth of that density; but it might be supposed that when so far relieved from pressure, the molecule could expand in proportion to the relief, especially if its form were that of a vortex ring, or of a hollow sphere. However, should this supposition not be admissible, we shall see presently that it is not necessary. We know that as long as any degree of heat remains in a gas collisions of its molecules will continue, dependent on their attraction for each other, which may drive them to any part of the containing vessel; and that it can only be when they are cooled down to the absolute zero of temperature that they can come to be at rest. But as we believe that the ether can never be reduced to this absolute absence of temperature, nor completely extracted from any vessel, we cannot acknowledge that the molecules of any gas, left along with it in the vessel, could ever come to be absolutely at rest, even although the molecules did not increase in volume with the diminution of pressure. And we think this conclusion will agree with the opinion of Professor Tait, expressed in the quotation, made at page 232, from his work on "Heat," where he says: "In fact, if the kinetic gas theory be true, a gas whose volume is immensely increased, cannot in any strict sense be said to have one definite pressure throughout." This, of course, is tantamount to saying that the diffusion of gases cannot continue to be always exactly regular at extremely low pressures, and must vary as the vacuum is increased; so that the volumes of the atoms and consequent displacements may continue always the same under all pressures. We see, then, from this quotation, that in all probability the molecules of a gas are not always equally buoyed up by the ether in a high vacuum; which very likely is the reason why there are dark streaks in it; streaks without any visible molecules of gas in them, because the ether was not dense enough to keep them afloat.

We have still something to add in support of what we said, at page 238, of glass not being pervaded by the ether, in the common acceptation of the word, and of our acknowledging that the ether might, in the course of time, ooze through it and fill up the bulb again, while air, gas and dust could not so ooze through it—nor even the larger particles of the ether; should we be forced to acknowledge that it consists of particles.

In one of a series of articles in "Engineering," Vol. XXV., on Repulsion from Radiation, we find, at page 155, what follows:

"With the same apparatus, Mr. Crookes conducted a long series of experiments for determining the conductivity of the residual gas to a spark from the induction coil. In air he found, at a pressure of 40 millionths (1/25,000th) of an atmosphere, which will be seen from the diagram, is the pressure at which the force of repulsion is at a maximum, that a spark whose striking distance at the normal pressure of the atmosphere is half an inch will illuminate a tube whose terminals are 3 millimetres apart. By pushing the exhaustion farther, the half-inch spark ceases to pass, but a one-inch spark will illuminate the tube, and as a vacuum is approached more electromotive-force is required to force the spark to cross the space separating the terminals within the tube, until at still higher exhaustion a coil capable of giving a 6-inch spark in air at the pressure of the atmosphere is required to show any indication of conductivity in the residual air. It was found, however, in experimenting with so powerful a spark that occasionally the glass was perforated by the discharge taking place through the bulb; but it is a remarkable fact that the perforation in such cases was so excessively small that several days were occupied before equilibrium of pressure was established between the inside and outside of the bulb."

Here we notice first—and it was the reason why we have made the first and longest part of the quotation—that the spark whose striking distance was half an inch at the normal pressure of the atmosphere, fell to under one-fourth of its power in a vacuum of only 1/25,000th of that pressure; that when a one-inch spark was required to illuminate the tube, it must have decreased to one-eighth in a vacuum of 1/50,000th; and, if it be admissible to follow the same proportion, the 6-inch spark must have been exhibited in a vacuum of 1/250,000th an atmosphere at least. Perhaps all this experiment was carried on in vacua produced by pumping alone, and the final vacuum may have reached a greater height than that which we have just mentioned; but the most interesting part of it is the perforation of the bulb by the 6-inch spark. In it we have to consider what was the conveyer which carried the electric spark through the glass of the bulb, instead of to the other terminal of the coil so close at hand, and it is a very difficult problem to solve. We naturally recur for some solution to the stratification of light given out when an electric current traverses a gas at very low pressure and gives rise to zones alternately light and dark as noted in the reference we made, at page 229, to Professor Balfour Stewart's experiments. We cannot think it unreasonable to suppose that the dark zones contained no matter at all that could be lighted up, and that it was the lighted zones alone which contained carrying matter for the electricity. If so, we can easily imagine one of these zones or strata carrying the perforating spark from the induction terminal to the nearest part of the glass of the bulb, for it was as possible for it to lie in that direction as in the direction of the other terminal, and the difference of distance between the first terminal and the glass, and between the two terminals, would not be so great as it appears to be on simply reading the accounts of the experiments; but we have still to think of how it managed to force itself through the glass of the bulb.

To get over this difficulty, we can refer to what we have said, that is, that glass may be thoroughly pervaded by the ether in an almost infinitesimal degree, and suppose that the electricity may have discovered, or rather been led to, the ether contained in the glass tube or bulb, and so found its way to one of the oozing holes we have said might exist in the glass; even the oozing hole may not have passed quite through the glass, and there might remain a very thin film to be burst open before perforation was complete. Also we may note that the zone which performed the office of carrier to the side of the bulb was much more probably composed of residual ether than residual air or gas, or at the least formed a preponderating part of the carrying element. The fact of the hole being so minute "that several days were occupied before equilibrium of pressure was established between the inside and outside of the bulb" on such occasions, goes far to prove that the carrying agent through the glass must have been the natural carrier of electricity, light, and heat. We cannot conceive that an eruptive force could open such a small passage through the glass of the bulb, but we can conceive that it should be able to force itself through a very minute passage already open, and even join two or more such passages into one. This conception makes us think of the many oozing passages there may be through a glass bulb; passages so minute that the ether might pass through them, but nothing so gross as any of our known gases; in fine, so minute that glass, for all the compact look it presents to us, may be only as a very fine sponge in respect to the ether. However, that the perforations related in the above quotation were large enough for air to pass through them there can be no doubt, otherwise the equilibrium between the pressures on the inside and outside of the bulb could not have been re-established even after many days; for there still remains the idea that the oozing holes might be so small that nothing but the ether could pass through them.

Should the glass of a vacuum tube or bulb be pervaded by the ether in the manner we have supposed it to be, and we believe there can be no doubt that it is so, it is obvious that its glowing when a current of electricity is passed through it must be caused by the electricity and consequently of its light, being carried into the body of the glass by means of the ether imbedded in, and forming a constituent part of, it. In connection with this we have to remember that the air in the tube does not glow when it is at full atmospheric pressure, but only when a certain degree of vacuum has been produced in it; and therefore it is equally obvious that it is only when the ether enclosed in the tube is reduced to the same degree of tenuity as that imbedded in the glass forming the tube, that the light of the electricity can be carried by it into the glass and make it glow. But to show this more clearly, it is necessary to refer to the steps by which we believe we have made very plain what must undoubtedly be the nature of the ether.

(1) First of all we have shown that, if there be such a thing as the ether, it can be pumped out of a close vessel of any kind; which proves that it must be a material substance, and in consequence can be expanded, or rarefied, and compressed the same as any other material substance; and that if there is no such thing, something else, having these qualities, has to be invented to take its place. (2) In showing this it has been made abundantly clear by the example of the hair of a cat in variable weather, to which we may add the exhibition of lightning in daylight, that it cannot make electricity visible, or illuminate any matter, unless the quantity of electricity it has to carry bears some certain proportion to the density of the ether in the matter that is illuminated. (3) In proof of this we have shown how, through its carrying power it can convey electricity of adequate force up to very great heights, so as to illuminate very rarefied air and cause auroras; the conveying being done either directly from the earth or by means of the ether mixed with the air carried up by whirlwinds to those great heights; and (4) how electricity is carried into the body of a tube of glass and makes it glow.

With these examples we can extend our ideas to other exhibitions of light, which, otherwise, we could hardly avoid looking upon as mysterious. We can see how marsh gas, rising up from boggy ground, becomes mixed with common air till it reaches a certain density, and forms the Will-o'-the-wisp when there is sufficient electricity in the air to make the diffused marsh gas visible, through the medium of the ether always mixed with it; or, perhaps, rather when the density of the diffused gas corresponds to the density of the ether. Then we have the phenomena of films of matter on the surfaces of certain liquids glowing with appropriate colours; which films must be pervaded by the ether in proportion to their conducting powers, the same as we have seen must be the case with all kinds of matter, the light given off corresponding as is natural to the composition of the films; and of course this same reasoning, or exposition, applies to the films formed on, or near, the surface of the sea which produce what sailors call "fire-on-the-wave." Lastly, and akin to the glowing caused in a vacuum tube, we cite the case of the glow-worm, the radiation from which must of necessity contain a certain amount of the ether in it, and may either glow constantly or intermittently according to its capacity for carrying electricity or light of any kind, constant or inconstant. Or if there is no radiation from it, its skin may possess the properties of a film on the surface of a liquid. We have seen in the "Times" of September 21, 1896, in its report for that day of the Meeting of the British Association at Liverpool, that in experimenting with glow-worms Dr. Dawson Turner had found some difficulty in getting them to glow when he wanted, but found they gave off the radiation whether glowing or not. Perhaps his interference with them destroyed the balance of force between the electricity present and the density of the ether in it without stopping the radiation.

Hitherto the light given out by a nebula, and any light of the kind not easily accounted for, has been attributed to incandescent gas not burning or being consumed, but only glowing. Now it is time to look upon it as belonging, at least in part, to the ether, and to look upon the bright line in the spectrum of a nebula as the Ether Line. We shall have to return to this later on.

We said, at page 248, that a fluid of some kind, elastic or not elastic, is necessary to enable us to pump solid matter out of a vessel of any kind, and went on to show that a gas as described by Dr. Crookes, or that can be described, in its own independent state of existence, by anybody, could not supply the want; because it consists of particles, molecules, atoms—any name that can be given to them—which have no power in themselves to move or to give motion to anything; they can be moved but cannot impart motion to anything, even to one another, until they are first set in motion by attraction. This in its turn led us to see that the only elastic fluid we have is the ether, and our work since then has taught us that we were wrong in saying at page 250 that a non-elastic fluid would suit for pumping solid matter out of a vessel; for we now see that what we have been in the habit of looking upon as non-elastic fluids, must owe their fluidity, such as it is, to the ether, which, in proportionate degree, pervades them the same as it does all other matter. In this way we are run down to the only conclusion we can come to, namely, that the ether is the only connecting medium and carrying agent of matter that we have, or even initiator of motion, except attraction; and being matter of the nature of an elastic fluid, there is no reason why we should not at once consider it to be attraction itself. It has been looked upon, for no one can exactly tell how long, as the connecting mechanism of the universe, thus having, in reality, assigned to it the attributes of the law of attraction, and all that we have to do is to put it in its right place. We are, in a manner, taught to look with suspicion on two agents being required to do one kind of work, or even two kinds of work that are so closely allied that we cannot separate them in a way that satisfies us; and this is precisely a case in which we can have one agent that can connect matter, and at the same time carry immaterial elements from one place to another.

Having got this length we have still to go one step farther. We cannot now doubt that the ether is a material substance, and if it is, there is nothing to prevent us from considering it to be the primitive matter; in fact it would be absurd to look upon it in any other light. We cannot conceive of anything having been created before the ether, or ordained before the law of attraction, and thus we have the two coeval and one. It is long years since physicists, chemists especially perhaps, began to think that the great number of chemical elements cannot all have existed from the beginning of things, and that it is far more probable that they have all been evolved from one primitive substance, and this idea must now be gathering more strength from day to day in view of the new elements that are being constantly discovered; the unknown is being made known, and the air we breathe instead of being one in four elements, as in former times it was considered to be, is now not far from double that number in one. Adopting this notion, then, the ether is much more likely to have been the primitive element than any other material substance that can be thought of. If it has never been thought of in this light, it has come to be very remarkably near it, as may be seen by referring to the long quotation we made in Chapter VII., beginning at page 129, where the idea of the ether being the connecting medium of matter is made use of to compute its density. Little thought we of this when we made the quotation, but there was the idea whether the author saw or not all that was implied in it.

Having broached the notion of the ether being the primitive element of the universe, or at all events, of the solar system, we might be expected to show how all the other elements were formed from it; but that has been done for us in a very much more able manner than we could have done it. Anyone who chooses to refer to "Nature" of September 2, 1886, will find—in Dr. Crookes's opening address, on Chemical Science in Section B, at the meeting of the British Association for that year—a very detailed explanation of how all the chemical elements might have been elaborated from one that he called Protyle; in which explanation he will only have to change this word into Ether to comprehend the process much more easily than by any exposition we could pretend to draw up. To quote the whole address would be altogether out of place, and besides, our notes of it are only fragmentary. But for present satisfaction of those who cannot immediately refer to "Nature," we may say that in the same report it is clearly stated that Sir George B. Airy was of opinion that all bodies may not be subject to the law of gravitation; and have no cause to think it strange we do not see that, were the ether and attraction one and the same, the whole universe would be finally collected into one mass, itself included. They will have better authority than ours for believing that the ether may connect matter evolved from itself, without being materially confounded with it. At the same time we acknowledge the necessity for expressing our idea of what we consider to be its nature, and in compliance with this obligation we say we have conceived it to be of the nature of indiarubber, not an elastic fluid as we have called it before, but rather an elastic substance like a jelly, as some people have conceived it to be; not a gas, because it does not require any medium to connect its particles.

Looking upon it in this light, action at a distance can be accounted for in a very natural manner. When a stretched indiarubber band is relieved from strain, the relief must be felt instantly throughout every part of its length; for, although the band may take time to contract, no time is required for the relief from strain being felt. In like manner an alteration in strain between the sun and the earth—and these alterations of strain are taking place every instant—connected by an indiarubber ether will be felt instantly in both bodies; and should anyone stand out for time being required to convey the attraction, let him remember that the difference of its power would be felt first at the two ends of the connecting medium, for the very good reason that even attraction itself could not prefer one extreme to the other. And that is all that is meant by action at a distance.

Here are some other things that could be explained more easily than they can be at present, through the ether and attraction being considered to be one and the same, than under any other conception we can form; but although we have a dim vision of such explanations in some cases, our knowledge of the sciences involved in them is not sufficient to warrant us in letting our dim conceptions see the light. Therefore all that remains for us to add is, that some things we have said of the ether may have to be so far modified now, but as they have had their part in leading us to the conclusions we have arrived at, they cannot be altogether suppressed.