36 



DR. F. HORTON ON THE EFFECTS OF CHANGES OF TEMPERATURE 



TABLE VII. Steel Wire. 



On plotting the values of the modulus of rigidity against the corresponding 

 temperatures a straight line was obtained. From this line the value of the modulus 

 at C. was found by exterpolation and then the true temperature coefficient a was 

 determined. The value found was a = '0002543, where n t = n (1 at). The value 

 of n at 15 C. was found to be n 1& = 8'4517 X 10 11 dynes per sq. centim., from which, 

 for the sake of comparison with the values for the other wires, the " coefficient " /8 

 was obtained, $ = '0002552. 



In determining the modulus of rigidity of the second steel wire with the later form 

 of apparatus, use was made of the fact that it had already been found to be a linear 

 function of the temperature. Observations were therefore taken at two temperatures 

 only, and from these the temperature coefficient was determined. 



The following are the means of several determinations at the temperatures given. 



TABLE VIII. Steel Wire. 



From these the value of the modulus at 15 C. was found to be n 15 = 8'13656 X 10" 

 dynes per sq. centim., and the " coefficient" /3 to be, /Q = '0002642. 



The results of the experiments by which the moment of inertia of the vibrator was 



