366 Prof. Wiedemann on the Magnetism of 



drawn into the use of any seeming asperity in my mode of allu- 

 ding to so eminent a teacher and meritorious and veteran an 

 author as Professor Young. The sole imputation which I meant 

 to convey when I hastily compared him with a class of indivi- 

 duals proverbially difficult to convince, was that of obstinacy in 

 his convictions, — a charge which his present honourable course 

 of proceeding triumphantly refutes. 

 K, Woolwich Common, 

 October 20, 1865. 



LII. On the Magnetism of Salts of the Magnetic Metals. 

 By Professor Wiedemann of Brunswick*. 



IN a series of earlier investigations the author endeavoured to 

 establish the properties of temporary and permanent mag- 

 nets, in so far especially as they can be explained on the assump- 

 tion of moveable molecular magnets. By this assumption the in- 

 crease of the temporary and permanent magnetic momentum with 

 increasing magnetizing power, its change by alternating action 

 of the latter in an opposite direction, and the mechanical and 

 thermal deportment of the various magnetized bodies can be 

 explained, at any rate qualitatively. For a further establish- 

 ment of this theory, as well as from a chemical point of view, it 

 appeared interesting to consider more closely the properties of 

 the feebly magnetized bodies, the salts of the magnetic metals, 

 and their solutions. Hence the magnitude of their temporary 

 magnetic momentum under various circumstances was deter- 

 mined. 



The measurements of this momentum were made with the 

 aid of a special torsion-apparatus. To a vertical brass pin, 

 moveable in a sheath, a German-silver wire was suspended, to 

 which was attached a long vertical brass bar, the lower end of 

 which was loaded with weights, and provided with brass paddles 

 which were immersed in a vessel full of oil. At the upper end 

 of the brass rod a mirror was fastened, by means of which the 

 rotation of the bar about its vertical axis could be read off by a 

 scale and telescope in the usual manner. On the bar, below the 

 mirror, and in a north and south direction, was a horizontal brass 

 arm about 20 millims. in length, to which was attached a small 

 glass flask filled with the substance to be investigated. In front 

 of this, and in an east and west direction, was a straight hori- 

 zontal soft iron bar rounded in front and surrounded by a mag- 

 netizing spiral, the magnetic momentum of which could be read 

 off in a mirror galvanometer placed in the direction of its axis. 

 After the magnetizing current was closed, by turning the pin 

 * From the Berliner Berichte, June 1865. 



