1070 Mr. D. Coster on the Spectra of X-rays 



light particle, the two would have parted company before 

 other light particles had impinged upon the rear of the first 

 one. The heavy particle would, in fact, be charged not 

 successively by single light particles, but by battalions of 

 them in column. Equilibrium would be reached when, on 

 an average, the columns were of mass equal to that of the 

 heavy particle. The equilibrium could occur even though 

 the velocities of the heavy particles were of the same order of 

 magnitude as that of the lighter particles. 



Under those conditions the law of final partition of energy 

 would be entirely different from that which would result 

 merely by making N large in the formula for gases. 



Whether this would give a credible picture of the aether 

 which would conform with other facts, it is not the intention 

 here to discuss. 



It would seem to imply a medium which would not be 

 quite like aether, a gas, or a liquid, or a rigid solid, but having 

 some of the properties of each. 



The only point insisted on here is that such a thing is 

 conceivable, and, although the Newtonian laws are assumed, 

 there would not be that frittering down of all energy into 

 the smallest movements. One exception alone is all that is 

 necessary to disprove the generality of the argument that the 

 Newtonian laws must always lead to this conclusion about 

 dissipation of energy. 



Conceptions of the aether on these lines may have been 

 thought of before. Novelty is not claimed, but the writer is 

 not aware that the bearing of such a conception on the theory 

 of partition of energy has been pointed out. 



CXV. On the Spectra of X-rays and the Theory of 

 Atomic Structure. By D. Coster*. 



[Plate XXIII.] 



Part I. 



Introduction. 



§1. A CCORDING to Bohr's theory of spectra the fre- 

 jMl quencies of the lines in the X-ray spectrum of an 

 element may be represented by the difference of two terms 

 which correspond to the energies of the atom before and after 

 the emission. Following Barkla's original notation for the 

 different kinds of characteristic X-radiation, the various 

 * Communicated by Prof. Sir E. Kutherford, F.R.S. 



