Magnetic Permeability of various Alloys of Iron. 8] 
It will be noticed that the conductivity of 1447 B in the unannealed state is much 
lower than 12871 in Series A, though both have nearly the same percentage of 
nickel. This is doubtless owing to the high carbon in the former specimen. 
So also the last specimen of Series A, 1449 A, with 31:4 per cent. of nickel 
(which might have been included in Series B), doubtless owes its remarkably 
low conductivity, in part, to the 0-7 per cent. of carbon which is added to the 
nickel. It may be that a carbide of nickel is formed in these cages, which, 
diffused throughout the steel, would produce a very high electric resistance. 
The specimen 1449 E owes its high resistance in part to the presence of 
manganese; it is really a nickel manganese steel, and as such is given again 
later in Group 12, p. 89. 
The alloy 1449 A was a ductile and beautiful material, and easily drawn 
into wire. A thin wire of this alloy was, therefore, made and submitted to 
further examination. Its electric resistance was carefully measured by the usual 
method, and the specific resistance found to have the large value of 86 microhms 
per c.c. at 15° C. This corresponds with the estimated specific resistance 
from the conductivity of a rod of the same material. The temperature co- 
efficient of this remarkable alloy was also determined, and found to be 0:09 
per cent. for 1°C. 
Enormous as is the resistance of this alloy, it is exceeded by another 
specimen which has more manganese and less nickel added to the iron; it is, 
therefore, a cheaper material, and has an equally good temperature coefficient. 
This specimen, marked 1414 B, contained 25 per cent. of nickel and 5 per cent. 
of manganese. It is, therefore, a nickel manganese steel, and will be referred 
to later on with others of the same class in Group 12. 
Tungsten Steels. 
We next pass on to the alloys of tungsten and iron. 
Group 4.—Tun@sTEN STEELS. 
Marks. Percentage Composition. Conductivity Copper = 100. Specific Seat yy outa 
Tun Mn C | Unann. Ann. Unann. Ann. ; 
1294 F 1:0 0-11 0°16 10°9 11-4 15°8 1571 
1294 H 3°5 0:28 0:28 8:0 9°6 21°5 18:0 
1294 I 7:5 0:20 0°38 7:0 8:9 24:6 19:2 
1294 L 15°5 0:28 0°76 4°8 6:4 85°7 26°6 
