BETWEEN LOXGITUDIXAL AND CIRCULAR MAGXETIZATIOXS. 289 



raagnetization due to a circularly magnetizing field was measured, 

 and compared witli tliat ol)tained hy the magnetometric method. 

 The results obtained by these two different methods nearly 

 coincide, showing that there is no trace of the effect of heating 

 as determined by the magnetometric method. 



To investigate the effect of the longitudinal field on the 

 circular magnetization of iron or nickel tube, I also wound very 

 carefully a secondary coil over the circularly magnetizing coil 

 and parallet to the tube, and measured the change by the 

 ballistic method. 



The total number of turns of the primary circularly mag- 

 netizing coil was 40 for the iron tube and 60 for the nickel tube, 

 and the mean field due to the current of one ampère was 17.7 C.G.S. 

 units for iron and 18.6 C.G.S. units for nickel. Owing to the 

 thickness of these tubes, the greatest deviation of the field from 

 the mean was 14 "/o for iron and 4.5 9ö for nickel. The number 

 of turns of the secondary coil for the measurement of 

 longitudinal magnetization was 30)3 for iron and 1,000 for nickel, 

 and that for circular magnetization was 100 for iron and 302 

 for nickel. 



II. Result of Experiments. 

 1. Iron Wire. 



The wire was first well annealed and put into the second- 

 ary coil, and the coil was thon fixed in the central line of the 

 magnetizing coil. After the wire was carefully demagnetized, it 

 was placed in constant magnetizing field. The longitudinal cur- 

 rent was then sent through the wire, and the correspond- 

 in«; throw of the ballistic 2;alvanometer was read. The wire was 

 again demagnetized and the same process repeated several 



