506 Mr. H. Tomlinson. The Influence of 



Fig 1. 



dition, passing through two apertures in a table, were secured at their 

 upper extremities to two clamps, A, and the lower extremity of the 

 one to be stretched was fastened to the clamp B, over which passed 

 the double hook S, connected with a stout lever of hard wood. A 

 scale-pan weighing 2 "kilos, was suspended at the end of the lever, 

 and by loading and unloading this very carefully the strip was sub- 

 jected to any required alteration of stress. Short pieces of insulated 

 copper wire were soldered to each strip at D, and the junction, C, of 

 these pieces was united with one terminal of the galvanometer. Two 

 other pairs of similar wires were soldered at K, and one of each pair 

 was connected as usual with resistance coils, and the other with one 

 pole of a single Leclamche cell. The two sets of resistance coils, which 

 in this case were about 10 ohms each, were united by a platinum- 

 iridium wire traversed by a sliding-piece connected with the other 

 terminal of the galvanometer. The mode of experimenting was pre- 

 cisely the same, and the same precautions were taken as in the earlier 

 experiments.* 



When the strip had been sufficiently tested in the unannealed con- 

 dition it was well annealed, and in this new condition again experi- 

 mented on ; but whereas before the stress used was not sufficient to 

 cause any permanent elongation, the strip was now permanently 

 lengthened and the permanent alteration of resistance thus caused 

 was measured as well as the temporary alteration. The following 

 experiment was made on the annealed metal when stressed for the first 

 time after the annealing. 



* Loo. cit., p. 45 and p. 54. 



