406 Messrs Kei Iokibe and Sukeaki Sakai : Effect of 



with the amplitude is found to diminish rapidly with the 

 length of the wire, and tends to become zero. In fig. C the 



Fig. 0. — Nickel wire. Diameter=0-5 mm. 



| s 



o 

 a 



.C 



5S A 



2 



lTtzttt: 



%0 60 80 IOO \ZpCm. 



Length of the iv;><? 



relation of the inclination <£ of the logarithmic decrement- 

 amplitude lines, expressed in seconds, to the length of a 

 nickel wire is graphically given. Thus, with an amplitude 

 of oscillations of 20 cm. on a scale placed at a distance 

 150 cm., the logarithmic decrement almost becomes inde- 

 pendent of the amplitude of oscillations if the length of the 

 wire exceeds 120 cm. Hence the logarithmic decrement 

 satisfying the theoretical conditions that it is independent 

 of the amplitude of oscillation, can be found by extrapolating 

 the logarithmic decrement-amplitude curves to zero ampli- 

 tude. It is also possible to find the logarithmic decrement 

 of the same nature by letting the system oscillate with a' 

 small amplitude ; but practically this method does not give 

 any accurate result, since the external disturbing effect is in 

 this case very prominent. 



A small part of the energy of oscillation is lost through 

 the support of the wire ; but this energy diminishes with 

 the increasing amplitude of oscillation. Hence the loga- 

 rithmic decrement deduced in the above way is quite free 

 from this sort of error. 



From the theory, it follows also that the logarithmic 

 decrement is inversely proportional to the weight of the 

 suspended load : in actual cases, however, it decreases 

 a little slower than the theory requires. In fig. 1 the 

 observed results for nickel and platinum are given. Thus 

 the logarithmic decrement of a wire is a quantity very 

 sensitive to its external conditions : that is, it varies with 



