Art. LI.—On Gravitational Experiments.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 17, 1884, Page 407

Art. LI.—On Gravitational Experiments. By T. Wakelin [Read before the Southland Philosophical Society, 7th October, 1884.] Professor Lodge in a recent lecture on the functions of the ether says it is inconceivable that the earth should be drawn to the sun without any material means, and he ascribes gravitation to some action of the ether. A great many scientific men, I feel convinced, sincerely hope that this may prove to be the case. I have thought out a number of experiments to test this question. Three of these experiments I have carried out but with negative results; two of them, however, were carried but in a very inadequate manner. I think an explanation of these and other experiments will prove interesting, and perhaps will arouse some hope that this fundamental question in astronomy may be answered. First Experiment, Heat.—If the ether produces the movement called gravitation, I thought it probable that any great disturbance of the ether should have some effect on the weight of a body placed in the midst of this disturbance. It struck me that as a red-hot mass of iron agitated the ether the reaction of the ether upon the iron would intensify the gravitational effect of the ether and cause the mass to weigh heavier. The molecular movement of a heated body would produce alternate increase and relief of pressure on the vibrating particle, and I thought it not unlikely that the former would be greater than the latter. As the experiment was easy I made it, though not with any degree of delicacy. There was no difference in the weight. Receiving afterwards Osmond Fisher' “Physics of the Earth' Crust” I was agreeably surprised to find in it the following passages:—“However, in a note to an address before the Geological Society of Glasgow, 14th February, 1878, Sir W. Thomson wrote: Since this address was delivered some important experiments have been carried out, at the request of Dr. Henry Muirhead, by Mr. Joseph Whitley, of Leeds. His experiments were made on iron, copper, and brass, and on whinstone and granite; and the general result hitherto arrived at seems to be that

these substances are less dense in the solid than in the liquid state at the melting temperature. And D. Forbes stated that glass floats on melted glass, and, similarly, Bessemer steel on melted steel.’” These facts indicated, I thought, that the intensely agitated ether had made the heated mass heavier: I therefore made a more careful experiment. A mass of iron was heated white-hot and weighed, the weight being over twenty pounds. After cooling for more than half-an-hour it was weighed again; and after being made cold in water it was weighed a third time, but there was found to be no distinct difference in the weight; if there was any difference, I think it must have been less than a quarter of an ounce. Both times, however, the iron, was weighed when cooling, while the reverse of this would have been more likely to show a difference in the weight. Second Experiment, Mechanical.—The ether is so marvellous that I should not have thought of trying to make any mechanical experiment if I had not read an account of the wonderful action of a saw called “Reese' Saw.” This saw was described as a disc made to revolve with an enormous velocity—at a velocity, as far as I can remember, of from one to two thousand revolutions per second. It was said to cut bars of steel without touching them. Mr. Reese himself ascribed this to the action of the disc upon the ether—the ether entering near the axis and being thrown out at the circumference, it was supposed. If any action of the ether produced gravitation I considered that this rapidly revolving disc should have very little weight. I thought by making the disc a very thick one that a moderate velocity would show some difference of weight. The disc that I had made was about seventy pounds, and could be driven so as to make about thirty revolutions per second. The oscillations were, however, so great that it could only be weighed when making three or four revolutions per second. Various modifications were made but with scarcely any improvement; no appreciable difference in weight could be detected. Experiments would have to be made with nicely fitting mechanism of a comprehensive character to enable a high velocity to be obtained, but a comparatively moderate velocity might produce an appreciable difference in the weight. Third Experiment, Magnetic.—Light, heat, magnetism, and electricity are believed to be manifestations of one agent—the ether. Now, if some action of the ether also produces gravitation, I thought it very probable that when a strong magnetic pull was exerted horizontally it would weaken that vertical action of the ether which I supposed might produce gravitation. I tried the experiment with a permanent magnet but with no definite result. I do not profess to be well acquainted with electrical facts, though I have read most of the best standard works on electricity and a good deal more besides, so an important experiment made by Faraday was unknown to me till the

last few weeks, when I saw the following account:—“The quality I refer to is ’electric conductivity’, and the result of that quality in the experiment I am now going to describe is, that a piece of copper, or a piece of silver, let fall between the poles of a magnet, will fall down slowly, as if it were falling through mud. I take this body and let it fall, many of you here will be able to calculate what fraction of a second it takes to fall one foot. If I took this piece of copper, placed it just above the space between the poles of a powerful electro-magnet and let it go, you would see it fall slowly down before you; it would perhaps take a quarter of a minute to fall a few inches.”** From Sir W. Thomson' “Lecture on the Senses,” published in “Nature,” 6th March, 1884. Professor Tyndall in one of his works speaking of this condensation between the poles of powerful magnets says that it takes as much exercize of force to make a knife go through this magnetic matter as it would take to cut a piece of cheese. My memory may be at fault here, but I am certain that he spoke of the resistance as something wonderful. Now this magnetic matter may displace a gravitational medium, or it may be connected with it in a way so as to weaken it. It seems to me, if one medium produces both electrical and gravitational effects, that if one effect is disturbed, the other must be disturbed also. Let us suppose the above experiment to be repeated with this modification. To the piece of silver placed between the poles, let another piece exactly equal be fastened by a wire long enough to let the second piece hang so far below as to be altogether out of reach of the influence of the electro-magnet; there is a resistance to motion of the piece of silver due to the thickness of magnetic matter. If the weight-giving force act equally on the two pieces of silver, the force overcoming the magnetic matter being doubled, the pieces of metal will fall about twice as fast as in the original experiment. If, however, the bodies are made to fall by some physical agent, then, if the magnetic matter displaces this agent, or modifies its gravitational action in the piece of metal between the two poles, the addition of the lower piece of silver has more than doubled the force, and the pieces of silver fall more than twice as fast. And if the experiment was tried, and this was found to be the case, we should reasonably infer that gravitation was produced by some physical agent. Fourth Experiment, Electrical.—The electric medium is believed to be continuous, just as the luminiferous ether is believed to be continuous. “We may say that all electric forces are transmitted by strains of the ether, but that the ether in different insulators is modified in some way which will account for the difference of transmission.”††A Physical Treatise on Electricity and Magnetism, by Gordon, p. 22. I suppose an electric

current in such a medium not to be a rapid motion of translation, but a transmission of preśsure, and believe in the opinion expressed by Silvanus Thomson, that electricity is one thing and not two. If the ether, then, among its other functions, produces gravitation, an intensification of its electrical action might reasonably be supposed to augment its gravitational action. Let us suppose a loop of wire to form part of a circuit, the loop being free to turn on an axis as the handle of a bucket is. When the loop is horizontal, like the handle of a bucket when resting on the rim, it must be supported, or else it will hang down. Let it therefore be supported from a delicate spring balance by means of a silk thread. If a powerful current be then sent through the loop, it will intensify the action of the ether, and if the ether produces gravitation the loop of wire should, I think, become heavier while the current was passing through it. Whatever gravitation may be, surely there is no reason to despair of finding out whether it is caused by something material or not.