165 



obtained by Nernst, Liirdemann and others for tlie sptH-ific heats of a large 

 number of substances including such anomalous substances as diamond. More- 

 over, by means of Einstein's formula it is possible to calculate the frequency 

 of the radiation emitted from the specific heat of a substance and the results 

 so obtained agree very well with the frequency as determined by optical 

 methods. It may be noted that the classical thermodynamics would lead one 

 to expect the specific heat of a substance to become zero at the absolute zero 

 of temperature. This is not tlie case and Planck's "energierest" would lead 

 one to suspect the truth. 



Stai'k'* has found that when secondary kathode rays are generated by 

 X-rays that the electrons in the secondary rays possess energy of the same 

 order of magnitude as those in the primary kathode rays which produce the 

 X-rays and that this does not depend upon the intensity of the X-rays. The 

 number of electrons in the secondary stream, however, does vary with the 

 intensity of the X-rays. This can be accounted for by saying that the quan- 

 tum possessed by an electron in the primary stream is handed on by the X-rays 

 to an electron in the secondary stream. Thus when secondary rays are pro- 

 duced the velocity of the individual electrons will not depend upon the in- 

 tensity of the X-rays but upon the size of the quantum. With more intense 

 X-rays more cjuanta are transmitted and more electrons set free. 



Paschen found that when canal ra}^s were examined for the Doppler effect 

 that, instead of having the original spectral line displaced to one side or 

 broadened on one side, he had a "rest," or undisplaced, and two displaced lines. 

 Stark" has pointed out that according to Planck's theory a positive ion will 

 only radiate when its kinetic energj' of translation is some multiple of the 

 "elementar-cjuantum." Conseciuently the ions which are radiating have 

 perfectly definite velocities depending upon the number of quanta they pos- 

 sess, and so we should expect to find a displaced line corresponding to each of 

 these velocities. Stark has also been able to calculate the velocity of the 

 radiating ions and finds that the results tend to confirm Planck's theory. 



Haber'" has applied the ciuantvun hypothesis to the absorption spectra of 

 solids and obtains an equation relating the wave-length in the infra-red, \r, 

 the wave-length in the ultra-violet, 'Kv, and the molecular weight, viz., Xr = 

 Xv X 42.81 I'M. This formula holds for i'(>gular crystalline substances such 

 as NaCI, KCl, and fluorspar. 



<Phys. Zeitichr.. 10, pp. 902-913, 1900. 



■'Ver'a. Deitich. Piys. Gei., 10, 20, pp. 713-715, 1908 



«Verh. Deitsch. Phy^. Ges., 13, 21, pp. 1117-1136, 1911. 



