GOG Flff*^ct of Teuipevature on Magnetic Change of B. est stance. 



greater tlinn in tlie case of iron, tlie curve l)('ing, however, of 

 a very different shape. The effect of stress is to diminish tlie 

 value of the change at all fields. The after-effect of stress on 

 the change of resistance was very small and appeared to he 

 in tlie same direction as the temporary effect. 



The residual change of resistance was also very small, and 

 was inappreciable when the wire was loaded. 



Some measurements were carried out on the effect of stress 

 on the magnetization of this specimen ; but, owing to the 

 small diameter of the wire, only approximate results could be 

 obtained. The effect of stress is to increase the magnetization 

 at low fields, and to diminish it at high fields. The residual 

 magnetism was inappreciable. The change of resistance in 

 two other specimens of nickel-steel was measured. The first 

 was a sample obtained from Messrs. Felten & Guillaume. 

 The change of resistance of this specimen was very small. 

 The resistance was increased at low fields, but the increase 

 reached a maximum at a field of 80, and then diminished 

 until it became zero at a field of 400. At higher fields the 

 resistance of the wire was diminished by magnetization. The 



maximum increase of resistance was -ry =4:'5xlO~^, and 



the decrease at a field of 800 was 4*9 X 10"^ 



The other specimen w^as obtained from Messrs. Hadfield of 

 Sheffield, and is manufactured by them under the name of 

 Eheostene. The change of resistance in this specimen is 

 still smaller. The resistance is increased at all fields, and the 

 curve is similar in form to that for Platinite. The maximum 



A-alue of the change is -j^- =1*8 x 10~^. 



Experiment IV. — The Effect of Variations of Temperature 

 on the Change of Resistance in Nickel. 



In all the experiments on the change of resistance at various 

 temperatures the ends of each of the wires experimented 

 upon were soldered to two thick copper wires which were 

 used for connecting to the bridge. The wire was then fastened 

 to a wooden lath, and was doubled up so as to bring the ends 

 as close together as possible in order to avoid thermoelectric 

 eflPects. The wire was heated up to a temperature of 100° C. 

 by passing a current of steam through the jacket of the coil. 



The curves in fig. 6 give the results obtained with nickel 

 Avire '35 mm. diameter. The wire was from the same reel as 

 the piece used in the stress experiments, but was not annealed. 

 It will be noticed that there is a slight difference between the 

 change of resistance at 15° C. before and after heating the 

 wire t-o 100° C. Very similar results were obtained by heating 

 a wire which had previously been annealed. The dotted curves 



