8 



MR. H. TOMLINSON ON THE INFLUENCE OF STRESS AND 



whether this special value represents a property of the material or is dependent on 

 the accidents of dimensions of the wire and moment of inertia of the vibrator. An 

 examination of the results recorded in Experiment III. seemed to indicate that the 

 damping was a maximum when the vibration-frequency of the wire was the same as 

 the reversal frequency. The following experiment was then made : 



Experiment VI. 



A fresh piece of the same wire was tested with two different vibration-periods, the 

 moment of inertia being altered by shifting the cylinders along the bar ; the magnet- 

 ising stress throughout was 46'025 C.G.S. units. 



The reversals of the magnetic stress were next made to synchronise with the 

 vibrations of the wire, the vibration-period being 4 '725 seconds. 



This experiment speaks for itself, and shows most conclusively that the damping 

 effect is a maximum when the reversal-period and the vibration-period synchronise. 



The experiment also shows that, with these high values of the magnetic stress, the 

 ratio of the logarithmic decrement to the magnetic stress diminishes very rapidly as 

 the latter increases. 



