220 



Mr W. S. HARRIS on the Heat excited in 



In the next Table are given the results of some few experi- 

 ments on wires of platinum and copper, of about the 7 Vth of an 

 inch in diameter. 



TABLE V. 



The conducting powers of the above metals, therefore, with the 

 decreasing force of the battery, constantly tended to a ratio of 

 equality ; and it was subsequently found, by employing more 

 delicate electrometers, by which a much less charge became ap- 

 preciable, that the indicated conducting powers were at last pre- 

 cisely equal. 



3d, The order of succession of some of the metals, as regards 

 their conducting power, was observed to be as follow : 



Silver, copper, zinc, gold, tin, iron, platinum, lead, antimony, 

 fl. mercury, bismuth *. 



* The conducting powers of antimony and bismuth have been determined sub- 

 sequently to the period at which this paper was read. These metals were cast into 

 bars, and compared with zinc, tin, and lead, treated in a similar way, a process 

 suggested to me by Mr FORBES, who was so good as to honour me with a communi- 

 cation on this subject. Mercury, in its fluid state, was examined in a somewhat 

 similar way, by causing it to form a fl uid bar of like dimensions to the preceding, by 

 means of a groove cut in a support of dry mahogany. The bars were each six 

 inches long, and about the one-eighth of an inch square. They were held securely 

 between stout forcep-wires, having compressing screws, as in m n, Fig. 3, so as to in- 



