198 Dr. TjTidall on the Progress of the Physical Sciences : 



The magnetism of the magnet, however, is in tnrn induced by 

 the stream which encircles it ; and the question will naturally 

 arise, whether by this mode of induction a point of saturation 

 may also be attained. 



The recent researches of M. Miiller fm-nish us with a prompt 

 affinnative reply to this question. In the investigation of Lenz 

 and Jacobi, already referred to, it appeared to be established that 

 the magnetic power evoked in the magnet was directhj proportional 

 to the stream which encircled it. M. JMiiller, however, proves that 

 in those cases only where the diameter of the induced core is 

 considerable does the law of the Russian physicists hold good, — 

 that thin bars have a point of saturation, beyond which additional 

 galvanic power does not materially increase the power of attrac- 

 tion. M. Miiller experimented with four cores of different dia- 

 meters ; it will, however, serve our present purpose to give the 

 results arrived at with his thickest and his thinnest core ; the 

 former was 44 millims. thick, and the latter 9 millims. ; both 

 bars were 560 millims. long. 



Bar No. 1. 



Bar No. 4. 



In these experiments the current passed from a battery com- 

 posed of six of Bunsen's cells round a magnetic needle (No. 1) 

 placed 50 feet distant, the tangent of the angle which the needle, 

 when under the influence of the ciu-rent, makes with the mag- 



