256 Magnetic Influence of Solar Light. 



TABLE XI. 



Shewing Duration of Oscillations of Needle D. after exposure. 



FExp.j 



Cm 



O . 



-2 X 



Hour of 

 Day. 



th of 

 die. 



Diam. of 

 Needle. 



j Temp. 



o ^ 



ition 

 scill. 



09 



O K 



Remarks. 



| No. ol 



P W 

 



A. M. 



P. M. 



Leng 

 Nee 



6 '8 

 zo 



ZQ 



No. 

 Trave 



1 



2 

 3 

 4 

 5 



Jan. 

 20th 







In. 



4 



In. 

 0.033 



97° 



10 

 10 

 10 

 10 

 10 



Sea. 

 262 

 262 

 262 

 261 

 261 



200 



. . . 













Sums. ... 



50 



1308 

















Means. ... 



i 



■t. 



26.116 







The needle D was partially oxidated on the surface, the 

 oxidation being distributed in small patches interspersed 

 with brightly polished spots. It is clear from the two 

 Tables, that no magnetic effect was produced upon it by 

 exposure, and this result was verified by means of the test- 

 ing apparatus formerly described. The experiments were, 

 however, varied in the following manner. A sewing nee- 

 dle 1 jf mcn long and | 2 of an inch in diameter was strongly 

 magnetised by the aid of a horse-shoe magnet, which being 

 placed on its centre, was made to traverse it backwards and 

 forwards for sometime, the needle being occasionally turn- 

 ed round, and care being taken to pass over each portion of 

 it an equal number of times, to insure equable distribution 

 of its magnetism. It ought farther always to be placed in 

 the magnetic meridian, and it may be useful to mention, that 

 when two common bar magnets are employed instead of the 

 horse-shoe one, to impart magnetism to a needle, their 

 opposite poles must be placed upon its centre, and themselves 

 being held inclined at an angle of about 23°, they must 

 be drawn along the needle in different directions, then lifted 

 perpendicularly, and carried well away from the needle, 

 until they can be brought down again upon its centre, when 



