226 MM. Reiss and Moscr on the Magnetic Influence 



magnetic intensity was concerned, by examining them some 

 time before using them ; and it was by this means that we ob- 

 tained decided results. The feeble magnetism of needles of 

 soft iron perhaps never reaches a fixed state. On this account 

 we have not given in the following tables the numerical results 

 obtained with this sort of needles. It may be sufficient here 

 to remark, that none of them, in the different circumstances in 

 which we exposed them, acquired, by the action of light, a de- 

 cided magnetism ; and that this might as well be attributed 

 to the variations which that property undergoes in iron by all 

 sorts of influences even mechanical ones. 



With regard to the following tables, we may add, that the 

 spectrum was almost always in its minimum of deviation, 

 (that is, the rays entered and emerged at equal angles from 

 the two surfaces of the prism,) which corresponds to its great- 

 est intensity ; — that the needles were placed upon a graduated 

 circle, three or four feet from the prism ; that the room was 

 in most cases darkened as little as possible ; and that the lens 

 had an aperture of 1.2 inches, and a focal length of 2.3 inches. 



