116 Prof. K. Honda and Mr. S. Konno on the 



that p can be expressed in the same form as q in terms of the 

 dimensions and the coefficient of viscosity of the wire, that is- 



TT^R 4 



v= — - — 

 The solution of the above equation is given by 



where is the initial amplitude of oscillations, T the period 

 of oscillation, and e a constant. 



If X be the logarithmic decrement, we have 



_pT _ 7r^R 4 T 

 or % 



Hence, by observing \ and T, i) can be obtained. In thi& 

 way, Messrs. K. Iokibe and S. Sakai * have already deter- 

 mined the coefficient of tangential viscosity for a number of 

 metals. 



Again, for the rigidity of the wire, we have 



_ 8ttI/ 



n 7r 2 

 hence - = t^t . 



7] lA, 



3. If the wire be replaced by a caoutchouc thread and 

 made to oscillate longitudinally in vacuum, the equation of 

 the motion of the suspended disk is 



L r d*x £$dx ES 



where M is the mass of the disk, x its displacement from the 

 position of equilibrium, E and S are the modulus of elasticity 

 and the cross-section of the wire respectively. The solution 

 of this equation is 



- 1^. (2irt \ 

 x = x Q e ^cos^-rp+ej. 



Hence X= 4/M 



or 



i= 



|ST 

 4/M' 

 4/A.M 

 ST 



* Iokibe & Sakai, in a paper which will appear in a forthcoming- 

 number of the Phil. Mag. 



