Magnetic Permeability of various Alloys of Iron. 97 
Group 26.—CHromiuM-MANGANESE-SILICON STEEL. 
Mark. | Percentage Composition. Conductivity Copper=100. | Specific resistance (calculated). | 
| Cr | Mn Si C Unann. Ann. | Unann. Ann. | 
608 | 2:0 4°25 1G} 1°32 2°5 3°3 | | 
68°6 62°1 
Group 27.—NickeL-MAncANESE-ALUMINIUM STEEL. 
| | 
| Mark. Percentage Composition. | Conductivity Copper = 100. | Specific resistance (calculated). | 
| | : | 
i 
| Ni Mn Al Si | C | Unann. | Ann. Unann. | Ann. | 
| 1411 14:1 5:3 2°3 0:61 | 0:43 | 1-94 | 3°6 88:7 | 47°8 | 
The above alloy, 1411, exhibits a remarkable increase of conductivity by 
annealing, amounting to no less than 87 per cent., notwithstanding the curious 
fact that the annealed specimen was harder to the file than the unannealed. 
Two sample rods of this alloy were made, one being annealed and the other 
unannealed, and their conductivities found as above; these were then reversed 
in their heat treatment, the unannealed specimen being annealed by slow cooling, 
and the annealed specimen heated and cooled quickly; on re-determining their 
conductivities a year later, precisely the same results were obtained as those given 
above, the now annealed specimen again being the harder of the two to the file. 
There was a considerable want of homogeneity in the physical condition of 
this annealed rod, one-half having a higher conductivity than the other. The 
mechanical and physical properties of these composite nickel steels need thorough 
investigation, as the results promise to be most interesting. 
Group 24 a.—NickEL-MancGanese-Copper STEEL. 
Mark. | Percentage Composition. Conductivity Copper =100.| Specific resistance (calculated). | 
| — = = | 
| Ni Mn Cu C | Annealed. | Annealed. 
1424B | 
| 
14:44 a9 2°25 0°83 | 2°15 | 80:0 
This specimen, 1424 B, should have been included in Group 24 on the last 
page: an error, made by the clerk who transcribed the chemical analysis, was not 
discovered until after the Paper had gone to press. ‘The specimen turns out to 
be, as the high electric resistance indicated, a nickel-manganese steel, similar to 
1109 D in Group 12, p. 89, to which 24 per cent. of copper has been added. ‘The 
effect of this addition is to reduce the resistance slightly. . 
