258 THE ATOMIC THEORY. 



shade into one another continiiousl}', but that they vary by leaps 

 which are .sometimes rehitivel}' large, and sometimes quite small. To 

 Mendeleeti" this irregular discontinuity is an argument against the unity 

 of matter, or rather an indication that the periodic law lends no sup- 

 port to the belief; but such a conclusion is unnecessary. If the funda- 

 mental matter, the '■'protyle,''as Crookes has called it, is itself discon- 

 tinuous and atomic in structure, the same property must be shown in 

 all of its aggregations, and so the difficulties seen by Mendeleeff dis- 

 appear. The chemical atoms become clusters of smaller particles, 

 whose relative magnitudes are as yet unknown. 



That bodies smaller than atoms really exist is the conclusion reached 

 by J. ,7. Thomson" from his researches upon the ionization of gases. 

 According to him, this phenomenon "consists in the detachment from 

 the atom of a negative ion," this being "the same for all gases." He 

 regards "the atom as containing a large mimber of smaller bodies," 

 which he calls "corpuscles," and these are equal to one another. "In 

 the normal atom this assemblage of corpuscles forms a system which 

 is electrically neutral.'' It nuist be borne in mind that these conclu- 

 sions are drawn by Thomson from the study of one class of phenomena, 

 and it is of course possil)le that they may not be tinally sustained. 

 Their value to us at the present moment lies in their suggestiveness 

 and in the curious way in which they reenforce other arguments of 

 similar purport. The possibility that the chemical atoms can ])e 

 actually broken down into smaller particles of one and the same kind 

 is, to say the least, startling, but it can not be disregarded. The evi- 

 dence obtained by Thomson is, so far as it goes, positive, and it is 

 entitled to receive due weight in all discussions of our present problem. 

 It is the tirst direct testimony that we have been able to obtain, all 

 previous evidence being either negative or circumstantial. It may be 

 misinterpi-eted, but it is not to be pushed aside. 



In direct line with the inferences of Thomson are the results obtained 

 by Rutherford and Soddy in their researches upon radio-activity. 

 Here, again, we have a subject so new that all opinions concerning it 

 must be held open to revision, but, so far as we have yet gone, the 

 evidence seems to point in one way. Ruthei'foi-d and Soddy* have 

 studied especially the emanations given off by thorium, and conclude 

 that from this element a new body is continually generated in which 

 the radio-activity steadily decays. This loss of emanative power is in 

 some sort of equilibrium with the rate of its formation. When tho» 

 rium is "de-emanated," it slowly regains its emanative power. The 

 emanation is a "chemically inert gas, analogous in nature to the mem- 

 bers of the argon family." The tinal conclusion is that radio-activity 

 may be "considered as a manifestation of subatomic chemical change." 



«Phil. Mag. (5), 48, p. 547. Also I'opnlar Scien<-e Monthly, August, 1901. 

 ''Phil. Mag. (fi), 4, pp. S9^, 581. 



