Elements in the Sun. 809 



current and reduces the available voltage ; hence r 3 should 

 be as small as possible, in order that for a given condenser 

 r. 2 and r 4 may be as large as possible. 



If we have to measure a condenser, it is easily seen, as 

 before, that we should choose a self-inductance coil with a 



large value of j^; so if we employ a variable self-inductance, 



it should be used near its upper limit. The larger the value 

 of L the higher will be the transverse impedance, but the 

 less the "lost volts" due to generator impedance. It is 

 probable that the largest available self-inductance will be 



considerably smaller than ^r~ ?j s ° the transverse impedance 

 J Ivor L 



due to it will not be very important, and its use will be 

 advantageous. 



We may conclude by summarizing these points as 

 follows : — 



(i) The frequency should be as high as possible. 



(2) R should be as small as possible. 



(3) ?\ should be about equal to I, the impedance of the 

 inductive arm. 



(4) ?' 3 should be small. 



(5) Since K is in most cases considerably smaller than 



— — 2 , it is best to use the largest available condenser for 



measuring a given self-inductance and vice versa. 



Physical Laboratory, 



Trinity College, Dublin. 

 September 8, 1920. 



XCIII. Elements in the Sim*. (Paper B.) By Megh Nad 

 Saha, D.Sc, Lecturer on Physics and Applied Mathe- 

 matics, University College of Science, Calcutta f. 



IT is a matter of common knowledge that the continuous 

 spectrum from the photosphere of the sun is crossed by 

 a number of dark lines, which are called Fraunhofer lines 

 in honour of their eminent discoverer. The correct inter- 



* Much of the introduction is taken, mutatis mutandis, from Fowler's 

 Report on the subject ; vide ' Journal of the British Astronomical 

 Society,' May 1918. 



t Communicated by the Author. 



Phil. Mag. S. 6. Vol. 40. No. 240. Dec. 1920. 3 G ■ 



