Magnetic Influence of Solar Light. 



263 



light than we formerly obtained. There is, however, one 

 point of difference between the last Table and those shewing 

 the action of the wires having smooth polished surfaces, 

 somewhat anomalous in its character ; and that is, that 

 while in the former case, increase of height of the wire pro- 

 duces a perceptible effect in increasing the duration of the 

 oscillations of the testing needle, in the latter it appears to be 

 perfectly indifferent to such increase, the times continuing 

 the same while the heights vary from |th of an inch to 6§th 

 inches. From Table xv. it appears, that while the height 

 of the wire varied from one to four inches, the durations of 

 oscillation exhibited a difference between the first and 

 fourth observation, of no less than thirty-three seconds in 

 the time of performing ten vibrations. 



Soft iron being more susceptible of magnetic influence 

 than steel, although less capable of retaining it permanently, 

 it appeared not unlikely that by employing it, the action 

 of the sun's light might become apparent, while by speedily 

 submitting it to the proper test, the acquired magnetism 

 would not have time to dissipate itself, and would accord- 

 ingly be recognised by the testing needles. Under this 

 impression, the following experiments were made, the iron 

 wires having each alternate inch roughly polished, the in- 

 tervening one being perfectly oxidated on the surface. 



TABLE XVI. 



Shewing Duration of Oscillations of Testing Needle, with soft iron wire 

 front, before and after exposure. 



Feb 

 5th. 



Hours of 

 Expos 



Temp. 



'■ Oh 



cqw 



59< 



83 c 



Q 



In. 

 0.166 



Ox. 

 Pol. 

 Ox. 

 Pol. 

 Ox. 



• Oh 



Q'uH 



