150 * 



Mr. G. M. Minchin. 



[May 16, 



which is always opposed to the E.M.F. generated by light. In this 

 case it was represented by 11'2 mm. 



The second column of this table contains the number on the scale 

 at which the spot stood when the cell was in the dark, i.e., when the 

 only E.M.F. in it was its disturbing E.M.F. ; the second column 

 contains the number to which the spot moved when the light of the 

 star was allowed to fall on the sensitive surface in the cell. 



It will thus be seen that the E.M.F. due to Regulus in these two 

 experiments was represented by the number 4'25, or about 4-25/530 

 of a Leclanche. 



Arcturus when tried gave the following results, after a few pre- 

 liminary observations (which were tried in the case of Regulus also, 

 and which are rendered necessary after the disturbances caused in 

 shifting the telescope, &c.) : 



These observations were somewhat irregular, because the sky was 

 not quite clear during most of the observations, but was getting 

 clearer as they proceeded. 



The last was probably the best observation, and in that case 

 Arcturus produced a voltage of about O02. 



An experiment was made to try whether, if the cell were exposed 

 to the sky in the neighbourhood of the star, but not to the star itself, 

 any effect was produced, and a deflection of about 0'5 mm. in the 

 direction opposed to that of the deflection caused by light was con- 

 stantly observed. 



