358 



REFOKT 1864. 



ment of the resiilts. Another ^\'ire was drawn as rapidly as possible through 

 the latter holes to harden it, and a difference of 3| per cent, was found in 

 its conducting power. 



The results are given in the following Table : — 



No. III. 0-9986. 



Copper. 



Three copper wires were tried. The copper employed was electrotype 

 copper, and it was drawn Avithout pre%-ious fusion. The copper of wires 

 Nos. I. and II. was prepared by Messrs. De la Eue &, Co., that of No. III. wire 

 as follows. Sulphate of copper was made by dissolving electrotype copper 

 in pure sulphuiic acid, and twice recrystallizing. The copper was obtained 

 from the sulphate thus prepared by electrolysis. It was precipitated on a 

 greased platimim pole, the other pole being of electrotype copper. 



