Magnetic Influence of Solar Light. 



261 



meridian, and inclined in a direction approximating to that 

 of magnetic dip, thus being in the very position of all 

 others most favourable for being influenced by the induc- 

 tive action of the magnetism of the earth, and consequently 

 for becoming a magnet itself. This is a very essential point 

 to be borne in mind^ and in a subsequent section of this 

 paper I shall have to point out how it has in all probabi- 

 lity so influenced the results obtained by Mrs. Somerville 

 and others, as to make it at least doubtful whether it has 

 not led them astray, by being the unrecognized cause of 

 those effects attributed by them to the action of light. The 

 circumstances I have just alluded to, rendered it essential 

 to repeat the experiments which appeared to favour the 

 idea of the magnetic action of light, and the same wire was 

 re-exposed 3 under proper precautions, its previous state 

 being clearly determined by the observations in the last 

 column of Table xni : it was however determined anew to 

 be certain against any intermediate changes. 



TABLE XIV. 



Shewing Duration of Oscillations of Testing Needle, with steel wire in front, 

 before and after exposure of the latter. 



f Exp.. 





Hours of 

 Exp. 



Temp. 



o . 





u 

 o 



6 



CO 



q 



•fOsc. 

 ! Exp. 



)fOsc. 

 Exp. 





CD 





Diam. 

 Wire 



° 6 



Oxid. 

 Pol. 



| No. o: 



"5 H 

 Q 



A. M. 



P. M. 



Befon 

 Exp. 



After 

 Exp 





| No. o 



Dur.c 

 before 



Dur. ( 



after 





Feb. 











In. 



In. 











1 



2 



10 





6 ° 



93° 



0.05 



7 



Ox. 



10 



69 



70 



2 





to 



m 











8 



ll 



8 



Pol. 



10 



70 



70 



3 















2i 



8 



Ox. 



10 



70 



70 



4 















3*. 



8 



Pol. 



10 



70 



70 



5 



... 













4 



Ox. 



10 



70 



71 



6 















4 



Pol. 



10 



70 



70 



7 



I 









1 







4 



Ox. 



10 



70 



71 



Remarks. 



2 M 



