436 SCIENCE PROGRESS 



such explanation would be necessary to account for the variation 

 in frequency and intensity of the sequence of pulses with tem- 

 perature, which is required to secure their agreement with the 

 law of radiation given by Planck. At any rate, the form of 

 Planck's law of radiation, with the distribution of energy per 

 wave-length constant for any particular temperature, combined 

 with the emission of energy by discrete quanta, which has been 

 satisfactorily confirmed, strongly suggests some kind of pulse as 

 the fundamental constituent in radiation. 



It would therefore be extremely desirable to determine from 

 Planck's law the form of pulse which would be in agreement 

 with the law at any temperature, as this might lead to important 

 information as to the actions going on within an atom to which 

 radiant energy is due. The difficulty of such a problem is 

 obvious, as the consideration of pulses all in one plane does not 

 seem to comply with the actual conditions of the mechanism of 

 radiation we have assumed. For the case of two dimensional 

 motion, however, the form of pulse required for agreement with 

 Wien's Law has been recently discovered by Dr. R. A. Hous- 

 toun, being published in Proc. Roy. Soc. He finds that the initial 

 form of displacement 



cos \ e 



b (h 2 + x)\ 

 where = tan -1 ^, leads to the expression for the energy per 



wave-length, 



E = constant x X e a, with c = constant 



From the point of view taken in this article, it is important to 

 remark that the above initial form is one of a series of initial 

 forms given by Lord Kelvin for " Initiation of Deep Sea 

 Waves" {Proc' R.S.E. 1906). 



An important aspect of the pulse hypothesis with regard to 

 the genesis of radiation referred to above is that the form of the 

 pulse is understood to be definite at any given temperature, and 

 accordingly the various characteristics of the pulse, or sequence 

 of pulses, which vary with the temperature may be used as a 

 measure of it. In the above, the variation of the constant h 

 allows for the representation of pulses belonging to different 

 temperatures, h being in fact inversely proportional to the abso- 

 lute temperature. We also have h| inversely proportional to 



