Magnetic Influence of Solar Light, 



377 



TABLE IV. 



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

 Before and after exposure. 



Medium Dark Red Glass. 



of Exp. 



Exp. 



Hours of 

 Expos. 



-d £3 



te of 



From 



To 



engt 

 Cyli 



[ No. 



Q 



A. M. 



P. M. 



m3 





Feb. 







In. 



] 



28th 



10| 





2 



2 











3 











4 











5 











a" 



In. 

 0-05 



Temp. 



£ o 

 •-2 »< 



03 X 



68° 



a? o 



eg Oh 



92° 



Sums 



Means 



Duration of 

 Oscillations. 



Before After 

 Expos. Expos. 



97 

 97 

 96 

 97 

 97 



484 



10 96- 



96 

 96 

 96 

 96 

 96 



480 



96 



Remarks. 



A high wind 

 prevailed at 

 first. Expos- 

 sure delay- 

 ed till wind 

 lulled. 



During the course of the forenoon on which this and the 

 succeeding series of experiments were made a high wind 

 prevailed^ from the influence of which upon the needle, a 

 difference of 6' or 7' in the periods of Oscillation before and 

 after exposure, was observed. As I had taken every possi- 

 ble precaution to guard against the interference of currents 

 of air, I at first thought I had obtained decisive indications 

 of magnetic action, and under this impression proceeded to 

 verify the results by means of the unmagnetic testing ap- 

 paratus. I was therefore somewhat disappointed, when I 

 could obtain no indications whatever of polarity by its means, 

 as I knew it was capable of shewing the presence of much 

 inferior magnetic intensity to that indicated by the above 

 mentioned difference. The experiments were accordingly 

 repeated after the wind had completely lulled, and the 

 result very clearly proves that in the first instance, a dis- 

 turbing cause had interfered, which no doubt was the wind. 



3 c 



