April 3, 1891.] 



SCIENCE. 



X. A common horseshoe permanent magnet, with legs about 

 six inches long, had perhaps fifty ohms of No. 32 wire wound 

 about the bend, and this was put in circuit with the telephone, 

 and struck like a tuning-fork. The sound in the telephone was 

 very loud; indeed, too strong to be held comfortably at the ear. 



XI. A coil of wire was now put about the middle of a piece of 

 gas-pipe, which was without permanent magnetism. The piece 

 of pipe was about four feet long and five eighths of an inch in 

 diametei'. This, when in connection with the telephone, was 

 struck two or three times a second with a piece of brass rod, and 

 while being thus struck it was rotated from the magnetic meridian 

 to a position at right angles to it. The difference in the loudness 

 of the sound, between the position in the meridian and away from 

 it, was very marked. It is therefore shown to be possible to de- 

 termine the points of the compass with a telephone, a coil, and an 

 iron rod. 



XTI. A second flexible ring was now made, about a foot in 

 diameter, consisting of a bundle of soft iron wire, the ends being 

 roughly braided and twisted together. The thickness of this was 

 rather less than half an inch. This was covered by a rubber tape 

 wound spirally round it, the better to secure stability of form and 

 insulation. Then 4 6 ohms of No. 31 wire were wound about it 

 its entire length, making probably a thousand turns. It was then 

 magnetized by a current from three secondary cells having six 

 volts, giving a magnetizing current of about thirteen hundred 

 ampere turns, leaving it a ring magnet. The terminals were then 

 connected with the terminals of a reiiecting galvanometer with a 

 resistance of .67 of an ohm. Very slight changes in the form of 

 the ring, either by pulling or pushing, gave decided movements 

 to the needle, while larger amplitude gave thirty to forty degrees' 

 deflection. 



XIII. It was noticed, also, that the direction of the current de- 

 pended not only upon the direction of the motion of changing 

 the form, but also upon the direction of the motion witli reference 

 to the normal shape of the ring. Thus, if the ring be a circle, 

 and it be drawn into a horizontal ellipse, the current will move 

 the galvanometer-needle, say, to the right. When it is brought 

 back to the circular form, the current is reversed. If the motion 

 be continued so as to produce a vertical ellipse, the current will 

 be in the same direction as that produced at first by a motion 

 exactly opposite in direction; so that for a complete cycle of 

 vibratory changes four currents are generated, — two direct, and 

 two reverse. 



XIV. One of the iron rings before mentioned, a-heavy one about 

 eight inches in diameter and an inch and a half thick, having 

 coarse wire wound upon it nearly covering the ring, was connected 

 with the galvanometer as before, and the ring was struck by a 

 brass rod. The needle instantly swung through a wide angle. 

 Struck again, it moved as before, but not through so wide an 

 angle, and a half-dozen blows knocked nearly all the magnetism 

 out of the ring. This was then detached from the galvanometer 

 and magnetized, as before, when it again gave the same large de- 

 flection it gave at first. The same conditions were tried with 

 other rings, and in each case it was found that a vigorous stroke 

 upon the ring magnet had the same destroying effect upon the 

 magnetism as it has upon magnets having external fields. 



XV. The flexible ring was now put in circuit again, and vigor- 

 ously jerked with the hands. A very few such movements served 

 to destroy nearly all the magnetism present, requiring the remag- 

 netization of the ring. • 



As flexible iron rings such as I wanted were not easy to make, 

 I procured some steel wire rope of the right size, and the ends 

 were welded for me through the courtesy of Professor Elihu 

 Thompson of Lynn by his electrical welding process. Such a 

 ring about a foot in diameter allows a movement of five or six 

 inches to one of its sides. This, when wound with four or five 

 hundred turns of No. 32 wire, may be magnetically saturated by 

 sending a current through the wire, leaving the ring charged. 

 The terminals may now be connected with a proper galvanome- 

 ter, and changes in the form will discharge the ring. 



These experiments prove, — 



1. That a change in the form of a magnet causes correspond- 

 ing change of stress in the field. 



3. That periodic changes in form due to elasticity of form, such 

 as are called sound-vibrations, set up similar periodic changes or 

 waves in the magnetic field. 



3. That such sound-vibrations of a magnet act upon other 

 magnets like sound-vibrations, and set them into corresponding 

 vibratory movements, sympathetic or forced, — sympathetic 

 when the receiving magnet has the same pitch as the transmitting 

 magnet, and forced when it has not the same pitch. 



4. That such sound-vibrations in the receiving-magnet cause a 

 corresponding change of form in its magnetic field, which mani- 

 fests itself by electric currents in circuits surrounding it. 



Sir William Thomson has frequently said that he could under- 

 stand a mechanical idea when he could make a model of it, but 

 could not otherwise. If one assumes that the ultimate atoms of 

 iron are magnets, as is thought most probable now, or holds, by 

 Ampere's hvpothesis, that currents of electricity circulate about 

 each atom, making it a magnet — in either case, each individual 

 atom has its own magnetic field, which is necessarily always with 

 it. It is really its re- action upon the ether. If such atoms be 

 elastic, as there is the best of reasons for believing, then it follows 

 that impact must set them into periodic vibratory motion; that 

 is, periodic change of form at a rate depending upon its degree of 

 density and elasticity. Such changes of form set up correspond- 

 ing periodic waves in the ether, as changes in the magnetic field; 

 and these are transmitted outwards with a rate depending upon 

 the properties of the ether to transmit such motions, not upon the 

 source of the disturbance. 



Such vibratory motions among atoms and molecules we call 

 heat, and such periodic waves in the ether we call light, and thus 

 Maxwell's idea of light being an electro magnetic phenomenon is 

 altogether in accordance with the experiments. For waves of the 

 lengths of light waves, it is essential that the vibrating body be 

 small and highly elastic. Maxwell's idea was, that the opposite 

 phases of ether-waves could produce opposite electrical effects, so 

 that each half-vibration represented either positive or negative 

 conditions; and these implied, though I have not noticed the 

 statement, that they inust have originated with vibrating mag- 

 netic atoms or molecules. It has been difficult or impossible 

 heretofore to imagine how ether-waves could be set up by vibra- 

 tions of the elements, though the idea that the atoms of matter 

 are magnets is not new at all, and has a good degree of proba- 

 bility. 



If one is to picture to himself at all how this kind of a 

 phenomenon can occur, he is bound to have in mind some form 

 for an atom that shall at the same time be a consistent magnetic 

 form. If atoms are magnets, it is well-nigh inconceivable that 

 they should be spheres or cubes, or tetrahedra, or disks^ or any of 

 the ordinary geometric forms, for such would be very poor forms 

 to exhibit magnetic properties. But a ring presents a very differ- 

 ent case, as a ring magnet is the most perfect form possible. 

 There is this to be said of such a form, however. It does not 

 present what we commonly call a magnetic field : it is a closed 

 circuit. 



Nevertheless, I would ask if it is probable that the ether ex- 

 ternal to a magnet of that form should be quite unaffected, quite 

 neutral. I should suppose not, but, on the contrary, should look 

 for some sort of stress there, though it might be of somewhat 

 different nature, and have somewhat different properties, from an 

 ordinary magnetic field. But if such were the case, it follows 

 that any magnetic change in the ring magnet itself would be fol- 

 lowed by a corresponding change in the external field, and vibra- 

 tory motions would necessarily set up waves in that field. Such 

 waves would have a magnetic origin, but the waves themselves 

 would not necessarily give rise to electro-magnetic effects directly. 

 Indirectly they would; for, if they could make another similar 

 magnet vibrate sympathetically, these vibrations would re-act 

 upon its magnetic properties. 



Such a ring form as I have shown suggests at once the vortex 

 ring theory of atoms, of the properties of which I have so often 

 spoken to the academy. Perhaps the experiments should have a 

 different interpretation from that suggested here; but, whatever 

 their interpretation may be, they are believed to be entirely new, 

 and therefore of interest, if not important. 



