364 



II. XAOAOTCA. 



The sudden twisting of the bar produced a large amount of 

 transient current, but the direction of the current was always the same 

 as with wires of smaller diameter. The only difference noticed by 

 twisting the wire was the quantity of the current developed. Noth- 

 ing differed from the results hitherto described. Professor Ewing 

 lias suggested that the twist applied by Matteucci was already beyond 

 the critical value, since the bar was very thick, and that consequently 

 the current most have changed its direction. In the above experiment 

 the bar was twisted through 90° (3° per cm.). This greatly exceeds 

 the twist applied by Matteucci, his limit being 20° in a bar GO cm. 

 long, or only 1° per cm. We cannot therefore explain the supposed 

 discrepancy in the direction of the transient current as the result of 

 a large twist. 



T<> shew the similarity of the effect obtained with the bar to that 

 obtained with the thin wire. I give the following readings taken in 

 varions magnetizing fields by the method of reversal. 



