Magnetic Permeability of various Alloys of Iron. 89 
on the conductivity than the much smaller quantities of silicon added to the other 
specimens. Compare also 1108 A and 1103 C, having nearly the same composi- 
tion, except that the latter has 1°25 per cent. more silicon—an addition that 
increases the electrical resistance 10°7 microhms for each 1. per cent. of added 
silicon ; whereas, in 1103 A and 1102 A, having the same quantity of silicon, 
the alloy 1103 A, containing 2°25 per cent. more nickel than 1102 A, has 
actually a higher conductivity. This is partly due to the fact that 1102 A. 
has 0:41 per cent. more carbon in the alloy than 1103A; and, as we have 
seen (p. 80), small percentages of nickel do not injure the conductivity of poor 
steels.* 
We now pass on to avery remarkable group, the nickel-manganese steels. It 
was found that excellent alloys could be made with large percentages of both 
these elements added to iron, and the result was a series of alloys, some of which 
were found to have an extraordinary electrical resistance. 
Group 12.—NickeL-MANGANESE STEELS. 
' — 
| Marks. Percentage Composition. | Conductivity Copper = 100. | La 
| 
| | ae fee anton c | Annealed: | Asragettet, 
| ion | too | 100 | 050 | 6-00 | 28-7 
| i952 @ | aon | ain 057 | 3°65 | 47-5 
1339 257 | 8:00 1-21 D5 70°2 
1313 C 900 | 10:25 | 1-40 | 2°30 | 74:7 
1109 D 1455 | 5:04 0-80 2:05 | 83-0 
| 14144 | 19-00 0A | OOO | 2°10 82:0 
1414B | 25:00 | 5-04 0-60 1:93 | 89-2 
149A 8140082 070 | 2-00 | 86-0 
| 1449E | 30:00 1-50 060 1:95 | 88:2 
The conductivity of 1414 A is rather higher than 1109 D, though it contains 
41 per cent. more nickel; tested by the file, it was harder than 1109 D: this may 
be due to a difference in thermal treatment, as the rod 1109 D was ‘“‘ water 
toughened.” 
Several of these specimens were drawn into wire, so that their sp. resistances 
*Tt is of course impossible to plot the relation between the conductivity and composition of these 
compound alloys, in the form of curves such as are given in Class I., owing to the variation in each of the 
two or more elements added to the steel. 
