252 



NA TURE 



[August 26, 19C9 



covery of corpuscles it had been shown by a mathematical 

 investigation that the mass of a body must be increased 

 by a charge of electricity. This increase, however, is 

 greater for small bodies than for large ones, and even 

 bodies as small as atoms are hopelessly too large to show 

 any appreciable effect ; thus the result seemed entirely 

 academic. After a time corpuscles were discovered, and 

 these are so much smaller than the atom that the increase 

 in mass due to the charge becomes not merely appreciable, 

 but so great that, as the experiments of Kaufmann and 

 Bucherer have shown, the whole of the mass of the cor- 

 puscle arises from its charge. 



We know a great deal about negative electricity ; what 

 do we know about positive electricity ? Is positive elec- 

 tricity molecular in structure? Is it made up into units, 

 each unit carrying a charge equal in magnitude though 

 opposite in sign to tliat carried by a corpuscle? Does, 

 or does not, this unit differ, in size and physical proper- 

 ties, very widely from the corpuscle? We know that by 

 suitable processes we can get corpuscles out of any kind 

 of matter, and that the corpuscles will be the same from 

 whatever source they may be derived. Is a similar thing 

 true for positive electricity ? Can we get, for example, 

 a positive unit from oxygen of the same kind as that we 

 get from hydrogen? 



For my own part, I think the evidence is in favour of 

 the view that we can, although the nature of the unit of 

 positive electricity makes the proof much more difficult 

 than for the negative unit. 



In the first place we find that the positive particles — 

 " canalstrahlen " is their technical name — discovered by 

 our distinguished guest. Dr. Goldstein, which are found 

 when an electric discharge passes through a highly rarefied 

 gas, are, when the pressure is very low, the same, what- 

 iver may have been the gas in the vessel to begin with. 

 If we pump out the gas until the pressure is too low to 

 allow the discharge to pass, and then introduce a small 

 quantity of gas and restart the discharge, the positive 

 particles are the same whatever kind of gas may have 

 been introduced. 



I have, for example, put into the exhausted vessel 

 oxygen, argon, helium, the vapour of carbon tetrachloride, 

 none of which contain hydrogen, and found the positive 

 particles to be the same as when hydrogen was introduced. 



Some experiments made lately by Wellisch, in the 

 Cavendish Laboratory, strongly support the view that there 

 is a definite unit of positive electricity independent of the 

 gas from which it is derived ; these experiments were on 

 the velocity with which positive particles move through 

 mixed gases. If we have a mixture of methyl-iodide and 

 hydrogen exposed to Rontgen rays, the effect' of the rays 

 on the methyl-iodide is so much greater than on the 

 hydrogen that, even when the mixture contains onlv a 

 small percentage of methyl-iodide, practically all the elec- 

 tricity comes from this gas, and not from the hydrogen. 



Now if the positive particles were merely the residue 

 left when a corpuscle had been abstracted from the methyl- 

 iodide, these particles would have the dimensions of a 

 molecule of methyl-iodide ; this is very large and heavy, 

 And would therefore move more slowly through the 

 hydrogen molecules than the positive particles derived from 

 hydrogen itself, which would, on this view, be of the size 

 and weight of the light hydrogen molecules. Wellisch 

 found that the velocities of both the positive and negative 

 particles through the mixture were the same as the veloci- 

 ties _ through pure hydrogen, although in the one case 

 the ions had originated from methyl-iodide and in the other 

 from hydrogen ; a similar result was obtained when carbon 

 tetrachloride, or mercury methyl, was used instead of 

 methyl-iodide. These and similar results lead to the con- 

 clusion that the atom of the different chemical elements 

 contains definite units of positive as well as of negative 

 electricity, and that the positive electricity, like the 

 negative, is molecular in structure. 



The investigations made on the unit of positive electricity 

 show that it is of quite a different kind from the unit of 

 negative, the mass of the negative unit is exceedingly 

 small compared with any atom, the only positive units 

 that up to the present have been detected are quite com- 

 parable in mass with the mass of an atom of hydrogen ; 

 in fact they seem equal to it. This makes it more difficult 

 NO. 2078, VOL. 81] 



to be certain that the unit of positive electricity has been 

 isolated, for we have to be on our guard against its being 

 a much smaller body attached to the hydrogen atoms 

 which happen to be present in the vessel. If the positive 

 units have a much greater mass than the negative ones, 

 they ought not to be so easily deflected by magnetic forces 

 when moving at equal speeds ; and in general the insensi- 

 bility of the positive particles to the influence of a magnet 

 is very marked, though there are cases when the positive 

 particles are much more readily deflected, and these have 

 been interpreted as proving the existence of positive units 

 comparable in mass with the negative ones. I have found, 

 however, that in these cases the positive particles are 

 moving very slowly, and that the ease with which they 

 are deflected is due to the smallness of the velocity and 

 not to that of the mass. It should, however, be noted 

 that M. Jean Becquerel has observed in the absorption 

 spectra of some minerals, and Prof. Wood in the rotation 

 of the plane of polarisation by sodium vapour, effects 

 which could be explained by the presence in the substances 

 { of positive units comparable in mass with corpuscles. " 

 This, however, is not the only explanation which can 

 be given of these effects, and at present the smallest 

 positive electrified particles of which we have direct ex- 

 perimental evidence have masses comparable with that of 

 an atom of hydrogen. 



A knowledge of the mass and size of the two units of 

 electricity, the positive and the negative, would give us 

 the material for constructing what may be called a mole- 

 cular theory of electricity, and would be a starting-point 

 for a theory of the structure of matter ; for the most 

 natural view to take, as a provisional hypothesis, is that 

 matter is just a collection of positive and negative units 

 of electricity, and that the forces which hold atoms and 

 molecules together, the properties which differentiate one 

 kind of matter from another, all have their origin in the 

 electrical forces exerted by positive and negative units of 

 electricity, grouped together in different ways in the atoms 

 of the different elements. 



As it would seem that the units of positive and negative 

 electricity are of very different sizes, we must regard 

 matter as a mixture containing systems of very different 

 types, one type corresponding to the small corpuscle, the 

 other to the large positive unit. 



Since the energy associated with a given charge is 

 greater the smaller the body on which the charge is con- 

 centrated, the energy stored up in the negative corpuscles 

 will be far greater than that stored up by the positive. 

 The amount of energy which is stored up in ordinary 

 matter in the form of the electrostatic potential energy 

 of its corpuscles is, I think, not generally realised. Ail 

 substances give out corpuscles, so that we may assume 

 that each atom of a substance contains at least one cor- 

 puscle. From the size and the charge on the corpuscle, 

 both of which are known, we find that each corpuscle 

 has Sxio-' ergs of energy; this is on the supposition 

 that the usual expressions for the energy of a charged 

 body hold when, as in the case of a corpuscle, the charge 

 is reduced to one unit. Now in one gram of hydrogen 

 there are about 6xio-" atoms, so if there is only one 

 corpuscle in each atom the energy due to the corpuscles 

 in a gram of hydrogen would be 48x10" ergs, or iixio' 

 calories. This is more than seven times the heat de- 

 veloped by one gram of radium, or than that developed by 

 the burning of five tons of coal. Thus we see that even 

 ordinary matter contains enormous stores of energy ; this 

 onergy is fortunately kept fast bound by the corpuscles ; 

 if at any time an appreciable fraction were to get free 

 the earth would explode and become a gaseous nebula. 



The matter of which I have been speaking so far is the 

 material which builds up the earth, the sun, and the stars, 

 the matter studied by the chemist, and which he can re- 

 present by a formula ; this matter occupies, however, but 

 an insignificant fraction of the universe, it forms but 

 minute islands in the great ocean of the aether, the sub- 

 stance with which the whole universe is filled. 



The rEther is not a fantastic creation of the speculative 

 philosopher; it is as essential to us as the air we breathe. 

 For we mast remember that we on this earth are not 

 living on our own resources ; we are dependent from 

 minute to minute upon what we are getting from the 



