120 Barrerr, Brown & Haprisup—On the Electrical Conductivity and 
nearly constant, the steel becomes much harder magnetically, the permeability 
falls rapidly, and the coercive force and hysteresis loss each rise to a high figure. 
The above table also affords an interesting comparison of the magnetic effect 
produced on a chromium steel by adding tungsten instead of nickel. In 1286A 
we have a nickel-chromium, and in 1189 B a tungsten-chromium steel of nearly 
the same relative composition. 'The last two specimens in Table XIV. show the 
effect of adding tungsten and then nickel to a manganese steel. The nickel- 
manganese steel is much worse magnetically than the tungsten-manganese steel. 
This difference is, however, probably due to the fact that the quantity of 
manganese is 14 per cent. larger in the former alloy. We have already found 
that when the quantity of manganese added to steel lies between 3 and 4 per 
cent., a great change for the worse is produced in the magnetic properties of the 
alloy, as will be seen by referring to Table IV. and Plate ITI. 
It is not therefore surprising that high nickel-manganese steels have an 
enormous electrical as well as magnetic resistance. Out of the group of nickel- 
manganese steels given in Group 12, p. 89, the following are practically 
non-magnetic in a field of 45, and, even when annealed, are only feebly magnetic 
in a field of 300 C.G.S. units. Beginning with the least magnetic, we have 
1109 D, 1414 A, 1414 B, 1339, 13813C, also the two manganese-tungsten steels, 
1343 B and 1343 A, given on p. 92, and the copper-manganese-chromium steel, 
1424 B, given on p. 97. In addition to the foregoing feebly magnetic steels, 
those manganese steels containing 13 per cent. of manganese and upwards are 
also nearly non-magnetic. (See Table IV., p. 108.) 
We do not propose, in the present paper, to enter upon a discussion of the 
interesting facts revealed by the above results, or the relative effect of different 
elements, when alloyed with iron, in reducing or destroying its magnetic suscepti- 
bility. We hope to return to this question in another paper. One element, 
aluminium, may actually increase the susceptibility of iron in comparatively low 
magnetic fields, and another, silicon, has the same effect still more conspicuously, 
as will be seen below. 
AppED NovemserrR, 1899. 
The group of steels contained in the next Table shows the most remarkable 
result we have yet obtained, the effect produced on the magnetic properties of 
iron by the addition of s¢dicon. Ordinary steel usually contains a small quantity 
of silicon, and it was noticed early in this investigation that the increase of 
silicon did not magnetically injure, but rather improve, a carbon steel; its 
magnetic effect appeared to resemble that produced by aluminium. 
