188 WEBER ON THE CONNEXION OF DIAMAGNETISM 



Diamagneto-electricity, — Measurement of Electric Currents 

 Diamagnetically Induced, 



The apparatus for diamagnetic induction to be first described 

 is so arranged that the induction is excited solely by the motion 

 of the diamagnetic body, while the spiral remains at rest, and 

 the diamagnetism of the body remains unchanged-, by this 

 means the formation of galvanic currents in the bismuth as a 

 conductor is avoided, and with it a secondary inductive action, 

 easy to be mistaken for the diamagnetic induction. The practical 

 construction of such an apparatus consists in the application of 

 a galvanic spiral, through whose electro-magnetizing force a bar 

 of bismuth placed in its centre may, as remarked above, be uni- 

 formly diamagnetized and moved to and fro within certain limits, 

 without suffering any change as to the strength of its diamag- 

 netism. 



The Electro-diamagnet made use of for the Diamagnetic 

 Induction, 



The electro-diamagnet made use of for diamagnetic induction 

 consisted of a bar of bismuth, a long wire spiral, h.cccc, fig 5, 

 Plate I., through which a current from eight of Bunsen's couples 

 was conducted. The bismuth bar was 186 millims. in length, 

 and weighed 339300 milligrms. The spiral consisted of cop- 

 per wire covered with wool, and afterwards coated with gutta 

 percha ; the pure copper wire was 2*3 millims. thick, and formed 

 eight layers one above the other, each of which was composed 

 of 120 coils. The whole spiral was 383 millims. in length, and 

 had an interior diameter of 239 millims., and an exterior diameter 

 of 70 millims. 



The Induction-spiral, 



The induction-spiral, Abbbb, fig. 5, Plate I., is that in which 

 a current is to be induced by the motion of the electro-diamagnet. 

 This spiral must be carefully insulated from that which belongs 

 to the electro-diamagnet, through which the current passes from 

 the galvanic battery, and connected with a multiplier, by which 

 the induced current may be observed. This spiral consisted of 



