Magnetic Influence of Solar Light. 



375 



trifling, that it may with confidence be inferred that no 

 change whatever took place in the magnetic condition of the 

 cylinder A, in consequence of its exposure for four hours to 

 the light of the sun, which was most favourable for the 

 experiment, the day being fine and clear, and the sky per- 

 fectly cloudless. And it now appears clear^ as will be still 

 farther confirmed, that the results obtained by the method 

 of approximation previously employed were erroneous, or at 

 least due to other causes than any power of imparting mag- 

 netism resident in the Solar Rays. Although theoretically, 

 the currents caused by the irregularity of temperature 

 throughout the cylinder, may influence the vibrations of the 

 testing needle, it does not appear from this table, that prac- 

 tically it does so, to any appreciable extent. It is just 

 possible, and nothing more, that the minute retardation 

 observed may be an effect of this cause, and since the co- 

 vered and exposed portions of the cylinder were placed 

 indifferently before the testing needle, the effect would 

 occasionally, as in the present instance, tend to retard, and 

 occasionally to accelerate the oscillations of the needle. 



TABLE II. 



Shewing Duration of Oscillations of Testing Needle with Cylinder B in front, 

 before and after exposure. 

 Medium Green Glass B. 





Ph 



Hours of 







Temp. 





Duration of 





of Exp. 



X 



H 



Expos. 



o 



go 



• = 









Oscill 



ation. 



Remarks. 



<~ 

 o 

 c 



From 



To 



S — 



g CD 



0 c 



"z 



© m 

 rt c 



O C 



o 

 z 



S3 

 P 



At M. 



P. M. 







pq m 



<& 



6 



z 



- 8* 



0 x 



<! 







Feb. 







In. 



In. 













Sunverybrislit 



1 



28th 



Ill 





2 



0-04 



73o 



91° 



10 



96 



96 



and powerful, 



2 

















1 10 



96 



96 



Sky cloudless. 



3 

















10 



95 



96 



4 

















10 



96 



96 





5 







::: 











10 



95 



96 

















Sums 





50 



47S 



480 















Means, ... 



10 



956 



96 





