'91 ^J AGGREGATES OF ELECTRONS. 359 



exist but its magnitude is quite small. It is of interest to see if it 

 is sufficiently large to account for the known cases in which the 

 dissipation of energy is smallest. These are unquestionly the cases 

 in which residual rays are obtained. I have developed a formula 

 which expresses the percentage of incident energy which goes into 

 the residual rays, which includes the case where dissipation is taken 

 account of. This formula leads to two separate methods of esti- 

 mating the order of magnitude of the dissipation. Both these 

 methods show that the dissipation must be of the order of lo^- in cer- 

 tain units where Planck's theory leads to a dissipation of the order 

 10* in the same units. Thus the source of dissipation pointed out 

 by Planck is about lo- times too small to account for the smallest 

 case of dissipation known to us. 



I am inclined to think that the most general type of absorption 

 of light by bodies of this class is of the following character. We 

 have seen that the electrons execute forced vibrations under the 

 influence of the incident light. When the period of the light ap- 

 proximates to the free period of the electron the electrons absorb a 

 great deal of energy from the light. In general this absorption of 

 energy will go on until the vibrations carry the electron out of its 

 region of stability. A rearrangement of the system will then take 

 place and during this rearrangement a great deal of the kinetic 

 energy which the electron has accumulated will be transferred to other 

 parts of the substance and will make itself felt as heat. As far as 

 that particular electron is concerned the sympathetic vibrations will 

 have to be established all over again. It is not necessary to suppose 

 that during this process the electron is actually carried out of the 

 atom when it breaks loose from the region of stability. The whole 

 occurrence may take place in the one atom. On the other hand we 

 know a great many cases of bodies which emit electrons under the 

 influence of light and in these cases the electrons must get carried 

 out of the atom. It seems to the writer to be an advantage 

 of this view that it connects the absorption of light with the so- 

 called photo-electric effect. As a first approximation this view of 

 the absorption of light leads to the same relation between absorption 

 and frequency as does the assumption of a retarding force propor- 

 tional to the velocitv. 



