976 Mr. M. Siegbahn on the Study of Variable 



V. Theory of the Phaseograph.' 



In theory the phaseograph can be treated in the same way 

 as the oscillograph. For the movable system the following 

 equation is obtained : — 



K dt> +A 3i +G *=* <!,) 



The letters signify : 



K, moment of inertia ; 

 A. damping factor : 

 I '. directive force ; 

 F, applied force. 



It' a Fourier's s< ries is put For F, 



F«2S* sin (*•*-&), .... (10) 

 tlic integral bo ( 9 ) w ill be 



» = C 2 V (i-yxy- + -iMP ,h '^-fe-7i)« (ii) 



If the mirror-oscillations are to represent the proposed 

 Fourier's series F, the integral 3 for a = l : 



»«=^2 r ^j 8 in(^-^^ 7i ) . . (15) 



must give the same curve as F. Any experimental test of 



this formula is almost out of the question. 



VI. Working of the Apparatus. 



"When using the apparatus it is necessary to ascertain if 

 the deviation is proportional to the strength of current. For 

 this purpose the ground-glass plate was replaced by a glass 

 scale, and simultaneous readings were made on this scale 

 (from any 0-point) and an ammeter. The following values 

 were obtained : — 



