308 PROCEEDINGS OF THE AMERICAN ACADEMY 



2G lbs. broke the wire. 



In all these experiments, it is easy to see that the change iu resist- 

 ance at first is not at all proportional to the increase iu length. At the 

 close of some of the experiments, the resistance is almost as much as 

 it ought to be ; and perhaps, if there were no error in observation or 

 calculation, the resistance at the breaking-point would be as much as 

 the law would make it. 



Experiment 5. — This experiment was made with copper wire not 

 so thick as that used in the previous experiment. I measured the 

 total length, and the changes in length ; so that, although not the whole 

 length is under the stretching process, the resistances given correspond 

 more exactly to the lengths given. 



1 6 lbs. broke the wire. I performed a second experiment with the 

 same kind of wire, and with essentially the same results. 



Experiment 6. — I next took German-silver wire. The curve of 

 observations here will be found to almost coincide with the straight line 

 representing the law. This experiment is quite curious when con- 

 trasted with the others. 



