﻿Torsional Oscillations of Wires. 



45 



at which the logarithmic decrement becomes constant was not 

 reached. The values of y for which x had the values 80, 120, 

 160, 180, 200, 220, 260, 300, were respectively 13'5, 10, 7*9, 

 7*2, 6'6, 6, 5, 4*4. The values of the differences of log y at 

 the extremities of the stretches of x 80-160, 120-200, 180- 

 260, and 220-300, were respectively proportional to 23, 18, 

 16, and 13. There is no approach to constancy, although the 

 average decrease of the range per oscillation during the last 

 40 oscillations was only one three-hundredth part of the 

 average range during these oscillations. 



The point will be considered further subsequently. 



Approximate Isochronism of the Oscillations. 



An experiment was made, immediately after the per- 

 formance of experiment M, to determine the period of 

 oscillation over different ranges. The numbers in the first 

 column below, when multiplied by 5, give the initial scale- 

 readings : in the second column are given the corresponding 

 times occupied by the next ten oscillations, the unit being the 

 second. In addition the zero was occasionally read, the 

 values being given in the third column. 



5-48 



790 



336 



5-50 



78-4 





5-84 



78-8 





512 



79-0 





5-30 



78-5 



3-36 



4-95 



78-8 



3-49 



7-15 



79-0 





1390 



79-8 





6-05 



78-5 





8-00 



79-4 





545 



78-5 



3-36 



615 



790 





14-90 



797 





480 



78-5 





6-60 



78-5 



3-43 



450 



78-5 





11-80 



79 5 





16-50 



80-2 





760 



79-1 



344 



7-80 



79-3 





1320 



80-0 





407 



79-2 



3-49 



7-65 



80-0 





1700 



804 





608 



79-8 





750 



79-5 











4-23 



78-8 



349 



Despite the irregularities inseparable from the conditions 

 of the experiment, it is evident that the period, while nearly 

 constant, increases slightly as the range increases. 



Damping due to the Viscosity of Air. 



In one experiment the surface of the oscillating part of the 

 apparatus was more than doubled by placing light sheets of 

 rough paper on the top of the lead ring. It was found 

 that this did not produce the slightest difference in the ob- 

 served ^ results. Thus the decay of the oscillations is not 

 appreciably affected by the viscosity of the air. 



