62 



AKT. ■!. — K. HONDA AND T. TERADA. 



JJV= ± 3.50 X lo'', 1= 16°.; C. 



In the above tables, N is the moment of Ibi'ce applied in 

 C.G.fS. units, and d the corresponding twist of the specimen as 

 calculated from the modulus of rigidity. The change of rigidity 



AT"- 



obtained by our direct method is denoted by .>- -, while that ob- 



oK' 



K,r' 



oK' 



tained by the indirect method, by -p— . The values of —r^- fairly 

 coincide with those obtained by the previous experiment ; but it is 

 to be noticed that the field here given is not the eifective one, but 

 the external field applied. The difference between ,^- and j^- 

 is remarkable ; its amount is of the same order of magnitude as 

 the change itself. The increase of the angle of twist slightly 

 affects the change of rigidity, always diminishing it in absolute 



AT"- 



amount. The general feature of -p- is quite similar to that for 

 nickel wire with weak tension, as obtained by the oscillation 

 method. 



It is curious to observe that the residual twist is always posi- 

 tive and uniformly increases with the field, as shown in Fig. G8. 



It may be noticed that the course of the curve of -p— close- 



