108 Barrett, Brown & Haprisenp—QOn the Electrical Conductivity and 
Taste 1V.—Alloys of Iron and Manganese (Plate I1I.). 
Mark. “Rovaoti, Tin Max. Induction, | Retentivity. | Coercive force. 
Iron (p) 0-03 17480 7120 1-66 
48  (p) 0-5 16700 8730 3-2 
4147 (p) 1:0 16200 9990 3-4 
58 (p) 2-25 15400 9900 6-0 
1379 B 3-5 12530 8950 17:8 
1381* 3°8 | 3300 1550 20-0 
39 (p) 4-0 9800 6080 16-2 
34 (p) 4-75 8730 | 5590 19°6 | 
945 A* (p) 7:0 | 4090 | 2320 20:0 
1379 D 10-1 670s 250 15-0 
1310 B* 115 | 1200 590 13:0 
13388  (p) 13-0 | 280 | f t 
1379 D/2 15-2 oO | } t 
30* 15°25 270 } rl 
598* 18°5 225 | 
From the above table it will be seen that a great drop takes place in the 
maximum induction, and a corresponding rise in the coercive force, when the 
quantity of manganese added to steel is somewhere between 3 and 4 per cent. 
The sudden rise in coercive force at this point is shown in fig. 12, p. 117. Upon 
referring to Plate III. the wide difference between the curves for specimens 
marked 53 and 39 is at once apparent. When the quantity of manganese in the 
alloy rises to between 7 and 10 per cent., further additions of manganese seem to 
have much less effect on the magnetic properties of the alloy; a 13 per cent. 
manganese steel, such as 1338, is practically non-magnetic. Upon referring 
to Plate II., showing the electric conductivity of manganese steels, the con- 
ductivity is likewise seen to decrease up to a 7 per cent. manganese steel, and 
then remains nearly constant up to the highest percentage tried. 
Judging from the specimens here tested, a remarkable feature in the magnetic 
properties of the high manganese steels is the part played by the presence of 
carbon. Although the specimen marked 1510 B has 1 per cent. more manganese, 
it is considerably more magnetic than 1379 D. On turning to Group 2, p. 76, 
* These specimens all contain high carbon from 0°78 to 1:66 per cent. See Group 2, series B, p. 76. 
+ The curves in the last four specimens lay so close to the axis H, that the values of retentivity and 
coercive force were too small to be correctly measured. 
