174 



C. G. KNOTT 



out later forms a part of a series of papers on the relations of mag- 

 netism and twist which I am communicating to the Royal Society of 

 Edinburgh. In the present note I wish to call special attention to one 

 point, namely the character of the lag in magnetic change due to 

 twisting. The peculiarity discovered by Mr. Imagawa was that, for 

 a particular amount of cyclic twisting, the curve showing the corres- 

 ponding changes in magnetic moment of the twisted wire, if regarded 

 as an area gone round in the proper direction, changed its algebraic 

 sign. This Mr. Imagawa established for iron and nickel wires, cir- 

 cularly magnetised by a current passing along them, and also for 

 nickel wire longitudinally magnetised by a current passing in an en- 

 closing helix of wire. Nearly all the experiments were made with 

 circularly magnetised wires ; and the few experiments with longi- 

 tudinally magnetised nickel were made with the view of finding if the 

 same curious reversal of magnetic lag was obtained with it. By a 

 strange oversight Mr. Imagawa did not observe at the time that cir- 

 cularly magnetised iron wire showed the same peculiarity as nickel ; 

 consequently he did not search for an analogous effect in longitudin- 

 ally magnetised iron. It was only when I came to collate the results 

 of all his experiments that the reversal effect was found to exist also 

 in the case of iron. By that time, however, the various effects of 

 twist on longitudinally magnetised iron and nickel wires had been 

 elaborately investigated by Mr. Nagaoka, whose paper follows imme- 

 diately on this one. It is because of the obviously close connection 

 between certain of Mr. Imagawa's observations of two years ago and 

 Mr. Nagaoka's more recent results that I have thought it well to dis- 

 cuss the former in this place. 



The particular class of problems proposed for investigation was 

 this : Study the effects of different twists upon the magnetic proper- 

 ties of different wires, along which currents of various strengths are 



