262 Magnetic Influence of Solar Light, 



From this Table it accordingly appears, that no increase 

 whatever took place in the intensity of the wire after far- 

 ther exposure, and it may therefore with safety be inferred, 

 that such exposure was not originally the cause of the mag- 

 netic phenomena it displayed, but that these were due, in all 

 probability, to the influence of the magnetism of the earth 

 upon it. The results in Table xiii. possess considerable 

 interest, however, because they prove clearly the susceptibi- 

 lity of the testing apparatus to small changes of magnetic 

 condition, and therefore justify us in placing considerable 

 confidence in its indications, while they farther shew how 

 important the interference of terrestrial magnetism with 

 such experiments may be. I do not feel competent to offer 

 any explanation of the causes of the peculiar distribution of 

 the magnetism throughout the wire ; but that the oxidated 

 and polished parts are invariably in opposite states, although 

 these states are not always of the same kind, is a remark 

 confirmed by all the observations that as yet have been 

 made on the point. The following Table exhibits the re- 

 sults obtained with steel wires, in which the polished por- 

 tions were roughly finished, and not ground smooth, as in 

 former instances. 



TABLE XV. 



Shewing the Duration of Oscillations of Testing Needle, with roughly polished 

 and oxidated steel wire in front, before and after exposure. 



Q 



Feb. 

 5 th 



Hours of 

 Exp. 



A. M. P. M. 



12 



Temp. 



©•!■»«■. 



Diam. of 

 Wire. 



Hts. of 

 Wire. 



Ox. or Pol. 



No. of Os- 

 cill. 



Dur. of Os. 

 before Exp. 



Dur. of Os. 

 after Exp. 







In. 



In. 











61° 



79° 



0-05 



1 



Ox. 



10 



63 



63 









2 



Pol. 



10 



71 



73 









3 



Ox. 



10 



81 



85 









4 



Pol. 



10 



9G 



96 



Wires prepared as the above, do not therefore give results 

 more favourable to the theory of the magnetic action of 



