to the Passage of an Electric Current. 



403 



W. Wooden block. 

 L. Leclanche cell. 



O, O. Resistances of 100 ohms each. 

 R. German silver used to balance wire. 

 C, C, C. Connecting-wires of copper. 

 S. Sliding scale. 

 G. Galvanometer. 



In this manner 4 pianoforte steel wires, 1 commercial steel wire, 

 3 iron wires, and 4 brass wires were examined with several different 

 weights. 



In the case of all the wires of different sections and materials, it was 

 found that the increase of resistance was exactly proportional to the 

 stretching-weight. In order to show this the increased resistance per 

 lb. weight for the different weights employed is given in the following 

 Table, for the first three steel wires examined, as with them a greater 

 number of different weights were employed than with the other wires : — 



