Magnetic Permeability of various Alloys of Iron. 

 Group 26. — Chromium-Manganese-Silicon Steel. 



97 



Group 27. — Nickel-Manganese-Aluminium Steel. 



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, pi-ecisely 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-Manganese- Copper Steel. 



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 2j per cent, of copper has been added. The 

 effect of this addition is to reduce the resistance slightly. 



