110 Barrett, Brown & Hadfield;— 0« the Electrical Conductivity and 



Table Yl.— Nickel Steels (Plate IV. 



Two or three of the above specimens are not shown on Plate IV., which already 

 is, we fear, somewhat overcrowded. The magnetic properties of the nickel steels 

 form a very interesting study from several points of view. It will be noticed that 

 the maximum induction for a field of 45 C.G.S. units is almost the same for the 

 specimens 1287 D and E as for good ii-ou, that is to say, up to nearly 4 per cent, of 

 nickel the maximum induction in a field of 45 C.G.S. units appears to be scarcely 

 affected, though, as will be seen from the next table, the permeability is some- 

 what less. The rather lower value of 1287 D in Table VI. is probably acci- 

 dental, and may be due to a physical diiierence in this specimen. As the nickel 

 increases from about 5 per cent, to about 18 per cent., the maximum induction and 

 retentivity both decrease, and the coercive force increases ; but with a still higher 

 percentage of nickel, whilst the induction remains about the same, the coercive 

 force suddenly falls : a remarkable softening of the steel, produced by the addition 

 of over 20 per cent, of nickel, is seen in the specimen 1449. It will also be noticed, 

 that as we pass from about 4 to 5 per cent, of nickel, a sudden increase in coercive 

 force takes place, indicating an equally sudden rise in hardness. This is well seen 

 in fig. 12, p. 117, which, however, does not show anything higher than 15 per 

 cent, of nickel. This sudden change, first from softness to hardness, and then 



* The B and H curve for this specimen in the annealed state is given on Plate V., owing to the 

 crowding of Plate IV. : the word 'unannealed' should have been added after '1449' in Plate IV. 



