76 Barrett, Brown & Haprietp—0On the Electrical Conductivity and 
added, or 6°6 microhms for 1 per cent. of carbon. 
resistance for a given increment of carbon being some four times greater in the 
former case than in the latter. This rapid fall of conductivity for the first small 
additions of carbon is seen in fig. 2 and Plate II. 
We will next take the alloys of Jron and Manganese, of which an extensive 
series was made for this investigation. This series may also be subdivided 
Alloys of Iron and Manganese. 
The rate of increase of 
into two groups, Series A and B, the latter containing higher carbon. 
Group 2.—Autoys or Iron and ManGanesE (Series A). 
Percentage Composition. 
C 
0°20 
0:24 
0:41 
0:08 
0°36 
0°36 
0°32 
0:15 
0:26 
0-15 
Conductivity Copper = 100. 
Unann. 
11:4 
6:9 
54 
5°65 
51 
4°5 
3°7 
3°7 
2-7 
2°56 
Ann. 
11-90 
7°30 
5°90 
5°80 
6:00 
5°86 
4:60 
5:10 
2°80 
2°65 
Specific resistance in microhms 
(calculated). 
Unann. Ann. 
14°96 14°46 
24:94 23°57 
31°86 29°18 
31°29 29°67 
33°74 28°69 
38°23 29°38 
46°50 37°41 
46°51 33°74 
63°70 61°50 
67:00 64:94 
AuLoys oF Iron AnD MAnGAnEsE (Series B). 
Percentage Composition. 
Marks. 
Mn 
48 0°50 
4147 1:00 
58 2°25 
1379 B* 3°50 
39 4:00 
34 4:75 
32 5°15 
13238 C 5°40 
1338 B/2 13:00 
1379 D/2 15:20 
Marks. 
Mn 
1420 A 1:00 
1381 3°81 
945 A 7°00 
1379 Dt 10-10 
1310 B 11°50 
1010 13:00 
30 15:25 
598 18°50 
C 
0°75 
0:78 
1:20 
0°16 
1°66 
1:23 
1:50 
1°54 
Conductivity Copper = 100. 
* 1379 B also contains 0°18 per cent. of silicon. 
+ 1379 D also contains 0°63 per cent. of silicon. 
Annealed. 
6:4 
39 
31 
2°7 
2°8 
27 
2°6 
2°5 
Specific resistance in 
microhms (calculated). 
Annealed. 
26°88 
44:12 
58°74 
63°72 
61:50 
63°60 
66°18 
69-0 
