Graded Series of Nickel-Manganese Alloys. 5 



The solenoid is first clamped in a convenient position, and a 

 current considerably greater than the greatest current to be 

 employed in the tests is sent through the coils Q 1} C 2 , and 

 the solenoid. Compensation, for the central position o£ the 

 spot on the scale, is then obtained roughly by moving the 

 coil Ci away from or towards the solenoid : the coil C x 

 is then clamped. The coil C 2 is now moved in or out 

 until the spot is brought back exactly to the zero of the 

 scale, and is then clamped in position. The effect of the 

 field at the needle due to the solenoid is now eliminated, so 

 far as the equilibrium position of the needle is concerned. 

 If, however, as is inevitable, the centres of the coils Ci and 

 C 2 , the needle and the axis of the solenoid are not in one line, 

 the balance will not hold for the deflected position of the 

 needle. The coil C 3 , the axis of which lies on the north and 

 south line passing through the needle, is now included in 

 the circuit, and, by means of a small magnet carried on a 

 stand, the spot is brought to one extreme position of the 

 scale. The coil C 3 is then moved towards or away from 

 the needle until no movement of the spot follows upon the 

 reversal of a large current in the circuit. This operation 

 having been completed, the magnetometer is in complete 

 adjustment. 



In the magnetic tests the specimen was mounted within 

 the magnetizing solenoid in the manner . shown in fig. 2. 



Fig. 2. 

 mz\ vztx vm 



Method of cooling the specimens to — 190° C. 



A is the specimen contained within a glass tube (BCD), one 

 end of which was closed, while the other end, CD, was open 

 and curved upwards. The tube was supported by cork 

 bungs, FF, so that the specimen lay along the axis of the 

 solenoid. Previous to being tested the specimen was sub- 

 jected to the action of an alternating magnetic field, which 

 gradually diminished from a large value to zero, that is to a 

 " process of reversals/' It was then tested at room-tempera- 

 ture. Liquid air was now poured into the tube, and the 

 specimen cooled to — 190° C. In all the experiments now 

 described the specimen was kept immersed in liquid air for 



