Magnetic Influence of Solar Light. 249 



Cafcis* of 3Zx$tximtnt$. 



I. — Experimental Needles of soft steel, and having brightly 

 polished surfaces. 



TABLE I. 



Shewing the Duration of Oscillations of Needle A. before exposure. 



)f Exp.l 



Date of 

 Exp. 



Hour of 

 day. 



Length of 

 Needle. 



Diam. of 

 Needle. 



S 



No. of 

 Oscill. 



Duration | 

 of Oscill. | 



). of 

 erses. 



Remarks. 



6 

 & 



A. M. 



P. M. 



$ 







1 



2 

 3 

 4 

 5 

 6 

 7 

 8 

 9 

 10 



Jan. 

 10th 



11 





In. 



4 



In. 



0«05 



63° 



5 

 5 

 5 

 5 

 5 

 5 

 5 

 5 

 5 

 5 



Sea. 



76? 



85? 



92 



99 



96 



97 



98 



97 



98 



99 



0 



Needle not proper- 

 ly adjusted. Ob- 

 servation reject- 

 ed. 













Sums, ... 



50 



861 















Means, ... 



1 



19-15 







This Table being the first, exhibits considerably greater 

 differences between the times observed than subsequent 

 ones do, as greater facility in reading off was gradually 

 obtained. From the circumstance previously alluded to, 

 of the watch employed to register the times, by having no 

 stop, single seconds may have occasionally been lost or 

 gained during the intervals of observation ; an error of 

 this kind would, however, compensate itself in a series of 

 observations, since the probabilities are as much in favour 

 of its being in one direction as the other. During the day 

 on which the above and succeeding Tables of Experiments 

 were made, the sun was slightly clouded, so, that both its 

 light and heat were to a certain degree interfered with. 



