Magnetic Permeability of various Alloys of Iron. : 109 
it will be seen that 1310 B contains 1°5 per cent. more carbon than 1379 D. 
Again, 1379 D/2 has low carbon, and the specimen marked 80, with practically 
the same amount of manganese, has upwards of 1 per cent. more carbon; the 
former specimen is non-magnetic, but the latter is slightly magnetic, as also is 
598, with 18°5 per cent. of manganese, and 1°54 per cent. of carbon. In the low 
manganese steels, carbon, as might be expected, decreases the magnetic induction, 
as will be seen by comparing specimen 4147 on Plate III., and 1420 on Plate V., 
both having 1 per cent. of manganese, but the latter having higher carbon. 
Even up to 33 per cent. manganese steel the presence of carbon injuriously 
affects the magnetic condition as seen on comparing 1379 B and 1381 in the 
above table. The magnetic measurements of these specimens have been repeated 
with concordant results. The hardness of these specimens, as tested by the file, 
precisely agrees with their relative magnetic conditions: thus the specimen 1381 
is considerably harder than 1379 B; and 1379 D harder than 1510 B; whilst 
598 and 30 are softer than 13879 D/2. The condition in which the carbon exists 
in these steels is obviously very important; the chemical analyses given does not 
show this, and this point requires further elucidation. 
The next table gives the permeability and hysteresis loss for those manganese 
steels given in Plate III. 
Tas_e V.—Alloys of Iron and Manganese (Plate I11.). 
Marks. Percentage of Mn. jo woe 1b = & Sete eee 
Tron 0-0 | 1560 | 11090 
48 0:5 1020 20460 
4147 1-0 1000 | 23090 
53 2°25 990 31860 
39 40 130 | 41070 
34 4°75 75 | 41000 
945 A 7-0 27 | 20460 
1338 13-0 0 | 980 
The permeability of the last specimen was too small to be measured as will be 
seen from Plate III. The rapid fall of permeability between 24 and 4 per cent. 
of manganese is remarkable; beyond this percentage the hysteresis loss diminishes, 
owing to the steel passing into a non-magnetic state. We will next take the alloys 
of iron and nickel. 
R2 
