Magnetic Permeability of various Alloys of Iron. 73 
CLASS I. 
Carbon Steels. 
Beginning with the Carbon steels, it is necessary to subdivide the specimens 
into two series, one of which (A) is freer from other elements, such as manganese 
and silicon, than the other series (B): as might be expected, the former has a 
higher conductivity than the latter. The chemical analysis in percentages for 
each specimen is given in the tables following, zron bemg understood in all cases 
to make up the total to 100. The last column gives the calculated specific 
resistance in microhms per c.c. at about 17°C. The letters Unann. and Ann. 
signify the conductivity in the unannealed and the annealed conditions respec- 
tively. 
Group 1.—CarBon STEELS (Series A). 
Marks. | Percentage Composition. Conductivity Copper = 100. Specific eieeay microhms 
C Si Mn Unann. | Ann. Unann. | Ann. 
*S.C.1. 0:028 0:07 Trace. 16°4 16°8 | 10°5 10°2 
*B, 0:03 0:14 0036 | 15°5 SU ikea 10:9 
*L.S.S. 0:05 0:02 0:18 14-9 15-2 11°5 11:3 
1166 A. 0:14 0:08 — 12°8 13°2 13°4 13:0 
1892 H. 0:78 0:10 0:10 10:7 11°8 16:1 14°6 
1392 I. 0°83 0:06 0°25 10°3 11°3 16:7 15:2 
1392 B. 0:84 0:20 0°18 10:0 10°7 Wie 16:1 
1392 A. 0°85 0:17 0°32 | 9°6 10°5 17:9 16:4 
1392 L. 1:09 0:17 0°32 9°8 10°6 17:6 16°2 
| 13892 G. 1:23 0:12 0:14 | 9°0 9°8 GPa 17°6 
\ 
It will be seen that the conductivity decreases as the percentage of carbon 
increases, at first very rapidly, so that the conductivity of chemically pure iron 
would certainly be higher than the specimen 8.C.I. The resistance of the 
specimen L.S.S. is a little greater than B., owing to the presence of a larger 
* A complete analysis of the first three specimens was made as follows :— 
Mark. (S Si S) 15) Mn Fe 
8.C.I. 0-028 0:07 0°005 0:004 Trace. 99°85 
B. 0-030 0-14 0:016 0:065 0.036 99°71 
L,8.S8. 0-050 0:02 0-011 0:013 0:180 99°72 
