On the Distribution of Energy in the Spectra of Solids. 425 



may be conceived of quite generally as the ratio of cause to 

 effect. 



That the objections to the employment of the term mag- 

 netic resistance have been founded on the assumed require- 

 ment of identity instead of analogy between the affections 

 of different subjects, and cannot be sustained. 



And that the extension of the employment of the term 

 Resistance in the above manner leads to some remarkable ana- 

 logies which go far to justify independently the employment 

 of the term Magnetic Resistance. And it has been pointed 

 out that the ordinary mode of statement involves inconsistent 

 and impossible ideas as to the relation of cause and effect 

 in the phenomena, whereas the application of the term 

 Magnetic Resistance compels us to precisely ascertain these, 

 and put them in their right places. 



Note. — An objection has been recently raised by M. Hos- 

 pitalier* to my definition of Magnetic Resistance, which comes 

 to this, that in defining the effect I take the induction through 

 unit surface instead of the total induction. This objection is 

 again based on the supposed necessity for conforming identi- 

 cally to Ohm's law in Electricity. The foregoing remarks 

 will have made it clear that I consider this unnecessary, the 

 question being, What is the most convenient measure of the 

 effect? Since the magnetic potential attainable is practically 

 limited, though it increases with the dimension, and the induc- 

 tion through unit of area practically attainable is also limited 

 (by saturation), the ratio of these two quantities lies always 

 within certain limits, though it increases with the dimensions. 

 In fact the magnetic resistance thus estimated is of linear 

 dimension, and may be regarded as of linear scale in plans. 

 If, therefore, this quantity be selected to be tabulated, the dis- 

 cussion of questions of design from a practical point of view 

 is greatly facilitated, and the relations of the quantities 

 involved are more easily followed and more simply expressed. 



LIII. Theoretical Essay on the Distribution of Energy in the 

 Spectra of Solids. By M. Wladimik MichelsonI. 



THE recent remarkable publications of Prof. Langley upon 

 the invisible spectrum $, and especially the promise of a 



* ' Electrician,' xx. p. 164, note. 



t Translated from the Journal de Physique, t. vi. Oct. 1887. Abstract 

 of a paper recently published in the Journal de la Societe Physico-chimique 

 russe, vol. xix. No. 4, p. 79 (1887). Communicated by the Author. 



X S. P. Langley, " Surles Spectres invisibles" (Ann. de Chim. et dePhys. 

 Dec. 1886, pp. 433-506). See also Amer. Journ. Sci. vol. xxxii. Aug. 

 1886 ; and Phil. Mag. vol. xxi. pp. 394-409, and vol. xxii. pp. 149-173. 



