Between the energy characteriqic Of the original X-ray and that amount of energy which was used up in the way just described, this energy it appears is found in the possession Of an electron whose velocity can be measured with accuracy. Here we have an extraordinary instance of a partition Of energy between wave and electron. We find the action of a wave resulting in the initiation Of both electrons and waves, but the simple relation which we had in the general case is only'modified to a slight degree. There may be several items instead Of one in our balance sheet, but the balance is still good. This action follows just as well as a consequence of the impact Of an electron having the necessary energy as it does from the incidence of an X-ray in the wayfl have described. We should 'notice in addition that when X-rays or electrons fall Short in their associated energy of the amount characteristic Of the atoms, there is no result at all, and this is re?ected in the fact that neither of them is absorbed in the atom SO much as if they were respectively a little higher in frequency or a little greater in velocity.