16 



Mr. Donovan on Galvanomctric Deflections 



auy influence in the resiilt. A wooden wheel four inches diameter, shod with 

 a rinw of bismuth weighing twelve ounces, was fixed on the axle of the revolv- 

 ing machine hereafter to be described. 



In revolving, the bismuth rubbed against the end of a cylinder of antimony, 

 and both the metals were connected with the galvanometer by capillary copper 

 wires, one of which was so contrived that it did not suffer by twisting as the 

 wheel revolved. The ring of bismuth, connected by its rheophore with the 

 zinc side of the galvanometer, was equally heated by a spirit lamp, while in 

 motion, its flat periphery being made to rub against the antimony. The needle 

 instantly moved to the east ; but as the motion of the wheel was continued, the 

 needle came round slowly to the west, and stood permanently at 65°, when the 

 antimony became heated nearly to the same degree as the bismuth. One of the 

 rlieophores, being bedded in the substance of the bismuth ring, must have been 

 at the same temperature as the bismuth: the other rheophore and the antimony 

 were similarly circumstanced. Here everything coincided with former trials. 



The next step in the inquiry was to make corresponding experiments with 

 various other associations of metals and alloys, in order to discover whether 

 their habitudes resemble those of bismuth and antimony. 



The following is a list of some metals which agree. Sometimes the revolv- 

 inof wheel was used, sometimes hemispheres, and sometimes plates: — 



Bismuth with antimony. 

 Bismuth with lead. 

 Bismuth with tin. 

 Bismuth with iron. 

 Bismuth with copper. 

 Bismuth with German silver. 

 Bismuth with nickel. 

 Bismuth with silver. 

 Bismuth with gold. 

 Bismuth with platinum. 



Bismuth with palladium. 

 Bismuth with hard amalgam of 



zinc and mercury. 

 Bismuth with cadmium. 

 Bismuth with arsenic. 

 Nickel with brass. 

 Nickel with lead. 

 Nickel with iron, 

 German silver with tin. 



On the collocation of the metals in the foregoing Table many particulars 

 depend, which may be thus classified: — 



1. If the first-named metal of each pair be connected with the zinc side of 



