(1 When the several hypotheses as to the con stitution of the negative corpuscle are judged by comparing these formulas with Kaufmann's experimental data, it appears (l ) that the Lo rentz corpuscle, which is the only one of the three that conforms with the theory of rela tivity, does not fit the data at all well; and (2) that the experimental evidence agrees quite well with either the Abraham or the Bucherer Langevin corpuscle.
From experiments of this nature we may obtain a certain amount of information with regard to the proportion of °electrical mass" to °real mass" in a corpuscle; for the experi mental data reveal the law in accordance with which the total mass varies with speed, while the theory of the nature and constitution of the corpuscle yields a formula showing merely how the electrical part of the mass varies. If there is a °real mass" to the corpuscle, we may there fore reasonably hope, by comparing experiment with good theory, definitely to solve this ques tion of the quantitative relation between the two kinds of mass. Kaufmann, soon after his original experiments were made, believed that they indicated that only a fraction of the total mass is electric;.but he had not then taken ac count of the difference (noted above) between longitudinal and transversal mass. Later, when due allowance was made for this difference, he came to the conclusion that most and perhaps a.1 of the mass is electric; and there is a growing tendency among physicists not only to accept this view with regard to negative cor puscles, but also to generalize it broadly, and to assume (at least tentatively) that mass, wherever it is found, is exclusively electrical in nature, and due to the motion, within the atoms of bodies, of electrified corpuscles moving with Feat speeds. This conception is as fascinat ing as it is revolutionary. Many of its advo cates, however, overlook the fact that even if this should prove to be the case, we have "ex plained" mass only by shifting it to the ether, which, at the same time, we should apparently have to conceive as a medium far denser than anything we know of, in the visible and tangi ble world of direct experience.
Before attempting to estimate the size of a negative corpuscle, it is netessary clearly to understand that we have no way, as yet, to determine the dimensions of corpuscles, if we assume that the mass that they possess is only partially electrical and that the rest of it is mass in the usual or non-electrical sense. If, however, we assume that the mass is wholly of electrical origin, we can easily obtain an esti mate of the size of the corpuscle. The value that we obtain will depend in some measure upon the views that we hold with regard to the shape of the corpuscle; but if, for present pnr poses, we consider it to be spherical, the esti mate of size obtained will probably be of the right general order of magnitude, even if the spherical shape ultimately proves to be unten able, so far as concerns the relation of the negative corpuscle to phenomena in general.
To obtain the desired estimate of size (in conformity with the assumptions here outlined) we may make use of the expression given by J. J. Thomson, and already quoted above, for the electrical mass of a slowly-moving electri fied sphere. Thus if to is the mass of the (stationary or slowly-moving) corpuscle in grammes, r its radius in centimeters and e its charge in absolute electromagnetic units, we have 2 2 e' --• •or 3 rt 3 sit Hence, with the values given above fore and in, we have r— 3 0.901 X 2 (1.592 X centimeters
In other words if 10,000,000,000,000 negative corpuscles were placed in a line and just touch ing one another, they would make a row about an inch and a half long. (An equal number of oranges, each three inches in diameter and placed in a row in like manner, would reach from the sun to the orbit of Jupiter). Atoms differ in size, but in a rough and general way it may be said that it would require something like 100,000 negative corpuscles, placed in a straight line and in contact with one another, to reach across the diameter of an atom.
The corpuscular theory has developed mar velously in the last 15 years, and it has been applied, in one form or another, to the explanation of the mechanism of many phe nomena, such as racliation, X-rays, radioactiv ity, and electrical and thermal conduction. It has also been pressed into service to explain chemical affinity and valency and to elucidate the structure of atoms and molecules. It has proved to be a fruitful conception, and some modification of it will no doubt remain with us, as a permanent addition to our physical the ories. It should be recognized, however, that when, in discussing particles so exceedingly small, we apply the general physical and me chanical laws and principles that we have de duced from observation in our grosser world of experience, we are very likely committing a serious error —an error which, though it will no doubt be corrected in the course of time, may be blinding us, meanwhile, to sotne very large facts. Many of the 'lbws)) that apply to larger masses of matter are probably statis tical laws, due to the averaging of many mil lions of separate events that do not individu ally follow these laws. That the properties of the negative corpuscle are far different from those that we have heretofore assigned to ((gross° matter is already sufficiently shown by what we have learned about the mass of such corpuscles. In a general way, however, it may be said that we have made progress enough in the study of the negative corpuscle to have it become a real thing to us—or at least a symbol of a real thing; and J. J. Thomson has well said that although the negative corpuscle is a recent discovery, we already know more about it than we do about the atom. See also ELEC TRICITY ; MOLECULAR THEORY ; RADIATION ; RA DIOACTIVITY.
creditable and interesting popular account of the negative corpuscle and its various relations is given in E. E. Fournier d'Albe's 'Electron Theory,) though the numer ical data therein given have now been largely superseded by better values, as indicated in the present article. A more recent and more au thoritative review of the relation of the corpus cular theory to physical phenomena in general is given by J. P. Minton in a series of papers printed in The General Electric Review for 1915 (Vol. 18.) Consult also Thomson, J. J., 'The Corpuscular Theory of Matter,) 'The Conduction of Electricity through Gases) and (Electricity and Matter); Campbell, (Modern Electrical Theory); Lodge, (Electrons); Lar mor, (Aether and Matter); Millikan, (The Electron); Comstock and Truland, (The Nature of Matter and Electricity); Bucherer, (Mathematische Einfiihrung. in die Elektronen theorie) Abraham, (Theorie der Elektrizitat) (Vol. if).