OX TRANSIENT ELECTRIC CURRENTS. 3 L9 



lines of compression, and the lines of stretching. Taking this as the 

 basis of our reasoning, let us examine what these curves giving the 

 relation between the current and the amount of twisting indicate. The 

 difference of magnetic susceptibilities along lines perpendicular to the 

 radius and inclined at 45° to the normal plane section of the wire 

 increases at first as t lie wire is subjected to greater twistings. This 

 différence, however, attains a maximum value. Hereafter the suscep- 

 tibilities along these two lines gradually tend to equality though very 

 slowly as the twisting is taken greater. 



Now let us analyze the susceptibilities along the directions of 

 stretching and of compression separately. We know that the suscep- 

 tibility increases with loading, but when the wire is stretched beyond 

 a certain limit, the susceptibility does not increase any more, and 

 begins to decrease. Although the stretching and compression caused 

 by twisting the wire varies at different distances from the axis of the 

 wire, yet on the whole the increase of twisting necessarily gives rise to 

 increased susceptibility in the direction of stretching until the 

 critical value of stress is reached. It is well known that this critical 

 point occurs with smaller amounts of pulling stress as the magnetiz- 

 ing force is increased. The consequence is that by twisting the wire 

 in strong magnetizing fields, the wire acquires the maximum 

 susceptibility in the direction of stretching for smaller amounts of 

 twisting. Accordingly if stretching was the only stress acting in 

 producing the circular lines of induction which produces the 

 transient current, we should expect to obtain the maximum current 

 at smaller twistings as the magnetizing force is taken greater. 



This is contrary to the observed fact, which is that the twisting 

 corresponding to the maximum current is increased with the strength 

 of the magnetizing force. Thus the effect of compression must play 

 an important part in changing the amount of the transient current. 



