MAGNETIC STRESS AND MAGNETIC DEFORMATION IN NICKEL. 
193 
Ai^'paratus. 
In the experiments nickel was used because the quantities to be measured are 
both greater and of a simpler nature than in the other magnetic metals. The 
specimen was an annealed wire of length 85'2 centims. and mean diameter 
1'65 millims., containing about 98 per cent, of nickel and traces of iron and cobalt. 
This was obtained from Messrs. Johnson, Matthey and Co. 
The magnetising coil was over a metre long, and consisted of seven layers of 
No. 18 copper wire wound on a hollow brass core provided with a water-jacket 
through which water could be made to flow steadily. The coil was mounted on a 
stand W (fig. 1) in a vertical position. 
Fig. I. 
The ends of the nickel wire N were soldered into two brass pieces, the upper of 
which. A, was a long cylindrical bar, and the other, B, a short block of brass 
prolonged downwards by a tube T'''' closed at the lower end. Both bar and tube 
fitted loosely in the core of the coil, the bar projecting and being fixed to a rigid 
* It was at first intended to measure Young’s Modulus for the nickel wire, a nieasui’ement for which 
the above apparatus was not very suitable, and which was moreover afterwards rendered unnecessary. 
MDCCCXCVII.—A. 2 C 
