Researches on Electro-magnetism. 197 



tion of the 12" bar in the last table, we see that with a ratio 

 between the currents of nearly 1 : 3 the cariying power increases 

 only in the ratio of 2 : 3, whereas to fulfill the law it ought to be 

 in the ratio of 2 : 18. 



The attractive force exerted upon a mass of iron is by no 

 means proportional to its weight. With a current of 20°, a 

 submagnet 6 inches long and 1 inch thick Avas attracted with a 

 force of 3-27 pounds; while one of the same length, and y^ths 

 of an inch thick, was attracted -milx a force of 4-91 pounds. 

 With a stream of 25° the former was attracted with a force of 

 6'8 pounds ; Avhde the latter, which was only about the eleventh 

 part of its weight, was attracted with a force of 8*24 pounds. 

 In like manner it was foimd that — 



A submag. 9" long and 1" thick bore a weight of 4'43 pounds, and 

 ... 9" ... -j^^ ... 6-00 ... 



Perhaps the most remarkable fact which these experiments 

 establish is, that there is a point of saturation, so to speak, for 

 soft ii'on, beyond which its receptivity for further magnetism 

 ceases. The following table exhibits this in a very striking 

 manner : — 



Attraction of submagnets 2 inches in length and of various diameters. 

 Diameters. 



Here the first three bars exhibit a considerable increase of 

 force, according as the stream strengthens, though still not suffi- 

 cient to satisfy the law of Lenz and Jacobi. above quoted. A 

 force of 20'', however, seems sufficient to saturate the last bar ; 

 for by an increase of galvanic power, which, according to the 

 said law, ought to make nearly nine times the attractive force, it 

 can scarcely be said that there is any increase at all. The same 

 occurred with bars 4", 6", 9", and 12" in length; in each case 

 a force of 20° seemed to saturate the j-fJ' bar to the full extent 

 of its receptivity. 



The above experiments, which appear to have been conducted 

 with considerable care, seem to establish the principle of satu- 

 ration. The manner of induction, however, is peculiar, this being 

 effected by the direct action of a magnet upon a mass of iron. 



