on the Thermo-electric Qualities of Metals. 



327 



10. The resistances of all the undrawn wires were carefully deter- 

 mined by the usual bridge method. 



The specific gravities and cross sections of both the undrawn and 

 drawn wires were also determined by weighing known lengths in air 

 and in water. The values are given in the following table. It will 

 be noted that the specific gravity of drawn copper, of drawn commercial 

 lead, of drawn platinoid, and of drawn manganin, is greater* than for 

 the corresponding undrawn wires ; that the specific gravity of undrawn 

 and drawn German silver wire is the same ; and that the specific gravity 

 of drawn reostene wire and of drawn pure lead wire is less than that 

 of the undrawn. 



* Average about a half per cent. 



