COSMIC EAYS MILLIKAN AND CAMERON 225 



responding to the huildi/ng up or creation of the abundant elements 

 like helium, oxygen, silicon, and iron out of hydrogen, or in the case 

 of the last two elements out of helimn. The entire annihilation of 

 hydrogen b}' the falling completely together of its positive and nega- 

 tive electrons might be an additional possibility, but it can be elimi- 

 nated in this case for two excellent reasons. The first of these rea- 

 sons is that there is practically no place whatever for such a radia- 

 tion to occupy in the observed ionization-depth curve (see fig. 1), for 

 it would be between four and five times more penetrating than the 

 radiation that has the smallest absorption coefficient mentioned 

 above. The ionization due to it, if it exists, would then have to be 

 included in the 2.4 ions, which represent the " zero of the electro- 

 scope " as shown in the figure. But this 2.4 ions is only about one- 

 tenth of the observed ionization at the top of the curve, viz, 21 ions, 

 this topmost reading corresponding to a depth of 1 meter below the 

 surface of Gem Lake. So that this hypothetical radiation can have 

 nothing to do with the observed ionization-depth curve much above 

 the reading 2.4, and below it there is, of course, room only for a 

 radiation relatively negligible in intensity in comparison with the 

 softer rays that are responsible for the observed curve. The second 

 reason is that this hypothetical radiation, if it were present, would of 

 necessity be homogeneous, and could not therefore exhibit the banded 

 structure shown by the observed cosmic rays. Whether then this act 

 of the entire annihilation of the hydrogen atom through the coming 

 into complete coincidence of the jiositive and negative electrons takes 

 place or not, it can certainly be eliminated as a cause of the ohserved 

 cosmic rays. There remains, then, no other atomic transformation in 

 which sufficient mass disappears to create the observed cosmic rays 

 except the aforementioned atom-building processes. It is important 

 to note that no step-by-step process of building up, or for that matter 

 of disintegrating, of atoms in which one positive electron or one alpha 

 particle is added or subtracted at a time will suffice for the generation 

 of the cosmic rays, since the Einstein equation tells us that in no case 

 can such a transformation produce rays of more than from one- 

 fourth to one twenty-fifth of the observed penetrating power. The 

 observed extraordinarily penetrating cosmic rays present, then, when 

 taken in connection with Einstein's equation and Aston's findings, not 

 only the first direct evidence that the more abundant elements are 

 now in process of being created out of positive and negative electrons 

 but they also present the first indications as to the general char- 

 acter of the specific act or acts by which the atom-building process 

 goes on. So far we have used only the general or qualitative evi- 

 dence, but it will be seen that from it alone the conclusion is scarcely 

 escapable that the powerful cosmic rays here studied can be produced 

 only by the creation in a single act, rather than by a step-by-step 



