404 Messrs. Kei Iokibe and Sukeaki Sakai : Effect of 



The period of oscillation was measured by the method of 

 timing in the same way as before. The logarithmic decrement 

 and its change with the amplitude of oscillation were deter- 

 mined by observing the consecutive amplitudes during a long 

 period of oscillations. 



The wires to be tested were all annealed in a vacuum in an 

 annealing furnace specially made, and then subjected to 

 experiments. The temperatures of annealing for our 

 specimens are given below : — 



Table I. 



j No. 



i 



Specimen. 



Annealing Temp. 



1. 



2. 



3. 



4. 



5. 



6. 



7. 



8. 



9. 

 10. 

 11. 

 12. 



Pt 



Pt-Rh 



about 1000° C. 

 1000 



800 

 800 

 800 

 800 

 400 

 800 

 300 

 300 

 300 

 not annealed. 



Steel 0-55% C. ... 



„ 0-90% C. ... 



„ 1-30% C. ... 

 Ni 



Cu 



Soft iron 



Au 



A S 



Al 



Zn 



For the torsional oscillation of the suspended system, it- 

 equation of motion is 



J d? +b dt +ae ^ 



where 



R 4 



21 ' 



n being the rigidity. The solution of the equation is 



= e 2i sin -^ 



jj t> 



