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DR. F. HORTON ON THE EFFECTS OF CHANGES OF TKMI'Kl; A '! 'I K'K 



The values of the logarithmic decrement are plotted against the corresponding 

 temperatures in Diagram II., the points marked being the first observation at the 

 ordinary temperature aud the values at the higher temperatures. 



Temperature Centigrade. 



Diagram II. Showing the effect of change of temperature on the logarithmic decrement of the 

 torsional oscillations of iron and of copper wire. 



The curve shows that the logarithmic decrement, and therefore the internal 

 viscosity of the wire, increases with the temperature, slowly at first but more rapidly 

 at higher temperatures. 



Soft Iron. 



This was the first wire in experimenting on which it was noticed that the period 

 of vibration at one temperature was not constant, but gradually diminislu-d ;is time 



