110 Barrett, Brown & Haprreup—On the Electrical Conductivity and 
Taste VI.—Mickel Steels (Plate IV.). 
Marks. Berean te (ce Mae piduction for) Retentivity. Coercive force. 
Tron 0:0 17480 7120 1°66 
1287 D 1:92 16750 8250 2°67 
9 3°82 17000 8350 2°76 
1267 B 4°75 11060 73800 14:28 
1287 I 11°39 8560 4790 17°33 
( 1447 B 12°1 4330 2370 22:4 
>» Unann. . 100 40 — 
1447 A PP 4630 2690 22:1 
| 5, wnann. | 5 195 73 — 
1287 K | 19°64 8100 4970 20-0 
| » Uunann. | 7 5940 3890 24:3 
1287 L | 24°5 4440 2820 22°5 
1449* | 31:4 2890 1100 0°5 
5 wnann. | 3 4680 1700 2:0 
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 iron, 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 difference 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 risein 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 LV.: the word ‘unannealed’ should have been added after ‘1449’ in Plate IV. 
