114 Barrett, Brown & Haprreutp—On the Electrical Conductivity and 
Up to nearly 4 per cent. of nickel the hysteresis loss increases but slightly, 
being less than that occurring with a corresponding addition to iron of any other 
element, so far tried, except aluminium and silicon. As before stated, an increase in 
magnetic hardness occurs at about 4 per cent. of nickel, and hence the hysteresis 
loss is seen to rise suddenly in the specimen 1267 B. The reverse effect produced 
by still larger additions of nickel is also well seen, the change taking place at 
about 20 per cent. of nickel. ‘The increase of permeability in the last specimen 
is remarkable, a rod of this alloy being practically saturated in a field of about 
16 C.G.S. units. Notice also the opposite effects produced by annealing in the 
different percentages of nickel. 
The great permeability of the low and very high nickel steels is remarkable, 
and ought to be determined for still lower magnetising forces. It was noticed 
that under the feeble force of the Earth’s magnetic field the high nickel steel, 
1449 (annealed), had a higher permeability than a specimen of the very best 
iron. In a future series of experiments the magnetic properties of these and 
the silicon and aluminium steels under small magnetic forces, and at different 
temperatures, will be investigated. | 
The effect of annealing on the magnetic properties of alloys is further 
seen in a striking manner in Plate V., which contains the B and H curves of a 
nickel chromium, and a manganese chromium steel, compared with good iron and 
a low manganese steel. 
Taste VIII.—Lfect of Annealing (Plate V.). 
Marks. | Percentage. eae #005 | Retentivity. | Coercive force. 
Ni. Mn. Cr. 
Tron | —- 17480 7120 1:66 
1420 | — 1:00 —_ 15000 8800 7:74 
+ 6 unann. — | 3 = 14000 10180 15°74 
1430 A* — | 3:09 8:92 13280 IO | Wises 
> unann. | —- | 55 3 470 Tt iT 
1450 A | 12°24 0:54 | 2:01 3720 1710 22°05 
5 wunann. | 16 5 ss 200 t iF | 
It will be seen that whilst the annealed specimens of 1480 A and 1450 A are 
magnetic, the former strongly so, the unannealed specimens are only slightly 
magnetic in a field of 45 C.G.S. units. In the steel 1420, with 0°5 per cent. of 
carbon, the coercive force is doubled in the unannealed specimen, that is to say, 
the hardness in the two states differs widely. 
* This specimen also contains 1:3 per cent. of carbon. 
+ These values were too small to be estimated, the specimens being almost non-magnetic, in the field, 
