IN TORSIONAL OSCILLATION 123 



been raised to a red heat in the electric furnace. The under- 

 noted work was undertaken to find the effect produced by a 

 repeated application of an extensional force and by a repeated 

 application of a twist to one end of the wire, the other end 

 being held firm, thus tending to induce fatigue in the wires, 

 the supposition being that such treatment might have an 

 effect on the mode of oscillation when tested immediately 

 afterwards. The latter step is necessary, since it has been 

 shown (Peddie, Trans. Roy. Soc. Edin., vol. xxxix., 1897- 

 1898) that rapid partial recovery from fatigue is possible. 



The apparatus used for imparting these continued strains 

 is a modification of an earlier machine used by Dr. Peddie 

 in these investigations, and was designed by him, the cost 

 of construction being defrayed by means of a Royal Society 

 grant given for the purpose. 



The accompanying photograph shows the complete 

 apparatus, with the battery and rheostat introduced 

 into the circuit. It consists essentially of an electrically 

 oscillated pendulum, which by means of a series of toothed 

 wheels at its mid-point twists one end of the wire introduced, 

 the other end of it being firmly clamped. 



EXPEBIMENTAL RESULTS 



Brass wire, similar to that used in the temperature experi- 

 ments, is the only wire yet tested, and experiments included 

 the finding of the effects on the constants n, a, and 6 of the 

 equation 



y n (x+a)=b 



after subjecting the wire (1) to rotational strain in the original 

 unheated state ; (2) to rotational strain after. the wire had 

 been raised to a red heat and cooled, i.e. after the points 

 obtained by plotting log (x+a) against log y could not be 

 fitted into one straight line ; (3) to extensional strain in the 



