October 14, 1904.] 



SCIENCE. 



499 



tion is into positive and negative parts and 

 that the same atom may be sometimes posi- 

 tive and sometimes negative. The idea of 

 a dissociation which occurs under the in- 

 fluence of a reacting substance appears 

 to be implied in a part of Professor Nef 's 

 discussion of methylene dissociation, but it 

 is not always clear whether he has in mind 

 chiefly a dissociation of this sort or one 

 which is independent of the interaction of 

 different compounds. 



The thought that the same atom may be 

 at one time positive and at another time 

 negative is related to the older electrochem- 

 ical theory which supposed water to be pos- 

 itive in acids and negative in bases. 



We assume, then, that in every combina- 

 tion of atoms each union involves an at- 

 traction between the positive and negative 

 electrons which are associated with the 

 two atoms that unite. In saying this I do 

 not lose sight of the fact that such a thing 

 as attraction per se in the sense that one 

 body can influence another at a distance 

 without an intervening medium is, appar- 

 ently, inconceivable. I think of the attrac- 

 tion as probably caused by some motion 

 of the electrons which enables them to act 

 on each other through the aid of the ether. 

 It is convenient, however, to speak of this 

 effect as an attraction, since our conception 

 of its real nature is, of necessity, very 

 vague. One advantage of the idea that the 

 attraction of the electrons is of a kinetic 

 nature is that we may conceive of the same 

 electron as becoming positive or negative, 

 according to the nature of its motion. 



The common conception, at present, is 

 that an atom which has lost an electron 

 becomes positive, while either the electron 

 in its independent existence or the atom to 

 which it is attached becomes negative. So 

 far as I am aware, it has not been pointed 

 out that this view leads to the conclusion 

 that the same atom must, under different 

 conditions, have a different weight. Thus 



a bivalent copper atom which has lost two 

 electrons must weigh less than a univalent 

 copper atom, which has lost only a single 

 electron. It is true that our methods of 

 determining atomic weights are scarcely ac- 

 curate enough to detect differences of this 

 order. The suggestion which is made is 

 that the electrons of two atoms which are 

 united have motions which correspond to 

 positive and negative charges, respectively, 

 and that when the atoms separate these 

 motions may be retained, or lost, as in the 

 case of a mercury atom which is uncom- 

 bined, or that the motions may be reversed. 

 In accordance with the hypothesis outlined 

 above, we must assume that when two atoms 

 separate either one may become positive; 

 dependent partly on their nature, partly 

 on the nature of the reacting substance. 

 The conception here proposed is that of 

 something very similar to the action of the 

 pole of a magnet, which may attract 

 another pole of the opposite kind, or induce 

 the formation of a pole of the opposite 

 kind, or it may reverse the polarity of 

 another magnet.* This is, perhaps, simpler 

 than to suppose the transfer of an electron 

 from one atom to another in those cases 

 where the electrical charges of the atoms 

 are reversed in the ionization. A very accu- 

 rate determination of the atomic weight 

 of cupric copper as compared with that of 

 cuprous copper might possibly decide be- 

 tween the two hypotheses. 



It should be noted that the hypothesis 

 that the electrical charges associated with 

 the atoms are of a kinetic nature, and that 

 these charges may be transferred without 

 gain or loss of matter, is quite independent 

 of the first hypothesis, which is that the 



* This is, of course, only an analogy and must 

 not be pressed too far; just as the electrical 

 changes of atoms or ions conduct themselves very 

 differently from those of masses. The latter 

 divide themselves between two bodies in contact; 

 the former may be transferred completely from 

 one ion to another. 



