On the Effects of Changes of Temperature on Metal Wires. 191 



at the two temperatures (16 - 1 C. and 87 C., and 15'4 C. and 

 87'7 C.), first with the lighter vibrator, then with the heavier. 



A mpiitudes 



Q IO 20 



DIAGRAM II. 



Steei. 

 3O 40 5O C 



60 



7O 



<50 C 



I 



p) 10 



20 



SO 





to 



Curtfe /; Te/tjo. f7-o 



2; 89-4 



,l8Lb.vjbraor 

 Id - 



Curves (1) and (2) of diagram III give the the first two sets of results, 

 (3) and (4) the second. It will be seen that the subsidence with the 

 heavier vibrator was more rapid at each temperature than with the 

 lighter vibrator. The logarithmic decrements are practically constant 

 throughout each of the two curves. 



A question arises here, which further experiments are being made to 

 answer for the different wires, as to the effect of repeated heatings and 

 coolings on the rate of dying out at any one temperature 1 Some 

 effects of this kind appear to be visible in the results obtained for one 

 or two of the other wires experimented on. 



Three pairs of curves are given in diagram IV() for commercial 

 copper, and were obtained with a 3'4 lb., a 12'7 lb., and an 18'7 lb> 

 vibrator respectively, and in this order. Here it will be seen that the 

 rate of subsidence is greater with each vibrator in the order of its 

 weight ; that is, the larger weight in each case corresponds to a 

 greater rate of subsidence, whether the temperature be the higher 

 or lower of those used in the experiments. Also the rate of sub- 



VOL. LXVII. P 



