70 Messrs. K. Honda and T. Terada on the 



the reversal of the magnetizing field, if it was repeated two 

 or three times, caused an equal deflexion o£ the galvanometer. 

 This method was found to be very sensitive, a very small 

 change of the current in the compensating system producing 

 a decided inequality o£ the galvanometer deflexions in 

 opposite directions. 



The tension effect was first tried. To wipe out any 

 uncertain remanent stress of the specimen, cycles of tensions, 

 from zero to the greatest to be used for the specimen, were 

 passed through before commencing any experiment. As a 

 preliminary test of the working of the arrangement, a series 

 of increasing fields was applied step by step under a constant 

 tension, and the increase of magnetization was observed by 

 the galvanometer. After a complete demagnetization, a weak 

 field was applied and kept constant. While the observer was 

 watching the galvanometer, the experimenter applied a series 

 of increasing tensions step by step ; the throw of the galva- 

 nometer at each step was recorded. Then the tension was 

 decreased step by step, and the corresponding deflexions were 

 sometimes noted. After passing through several cycles of 

 the tensions, the observation was repeated. After a complete 

 demagnetization, the procedure was repeatedfor another higher 

 field and so on. The number of fields chosen was naturally 

 large for the region where the change of magnetization was 

 considerable, but few where it was small. The magnetizing 

 current was found to remain nearly constant during an 

 experiment, except in strong fields, where it was sometimes 

 found to vary 2 or 3 per cent. The reading of the ammeter 

 was always observed both before and after the experiment, 

 and the mean was taken. 



Instead of increasing the tension step by step, the maximum 

 tension was often applied at once; but it was found that the 

 consequent deflexion of the galvanometer was nearly the 

 same as the sum of the deflexions obtained by the application 

 of tension in successive steps. 



Another series of experiments is possible in this direction. 

 The specimen was demagnetized with the smallest initial 

 tension ; it was then magnetized, and then the deflexion of the 

 galvanometer due to an additional weight was observed. After 

 several alternate additions and removals of the additional 

 weight, the changes of magnetization due to the addition and 

 removal were observed. Then the demagnetization with the 

 initial and added weights was effected, and the change of 

 magnetization due to a second additional weight was 

 measured, and so on. 



Next, the magnetization under constant tension was deter- 

 mined. The specimen was first thoroughly demagnetized by 



