78 Baekett, Brown & Hadfield — On the Electrical Conductivity and 



added manganese. The next six specimens in the same series show that an 

 increase of from 1 to 5*4 per cent, in the manganese causes the sp. resistance to 

 rise at the rate of say a quarter of a microhm for every tenth per cent., or 

 2'3 microhms for each 1 per cent, of added manganese.* 



Alloys of Iron and Nickel. 



The next group is an extensive and extremely interesting series of alloys of 

 Iron and Nickel : a large set of these alloys was prepared, ranging from one- 

 quarter per cent, to fifty per cent, of nickel. About one-half of the whole series 

 of specimens were tested for conductivity, these having been rolled into test- 

 rods 106 cms. long, and about half a centimetre in diameter ; some specimens 

 were also drawn in the form of wire. The conductivity of the test-rods measured 

 was as follows : — 



Group 3. — Alloys of Iron and Nickel (Series A). 



* The remarkable physical properties possessed by steel containing from 10 to 13 per cent, of 

 manganese were discovered by one of us upwards of twelve years ago. The electric resistance of a wire, 

 containing some 13 per cent, of manganese, was found to be 70 microhms per c.c. at 15° C. 



A complete analysis of this alloy showed its composition to be :— 



Manganese, 13-75 



Carbon, 0-85 



Silicon 0-25 



Phosphorus, . . . . . . 0-10 



Sulphur, 0-09 



Iron, 84-96 



100-00 

 This alloy was non-magnetic; its density was 7-81. The modulus of elasticity (Young's modulus) of 

 the wire in the hard state was found to be 1680 x 10'' grammes per sq. cm., and in the soft (or suddenly 

 cooled) state 1500 x 10* grammes per sq. cm. Unlike carbon steels, the high manganese steels are 

 rendered softer by suddenly cooling. The tenacity of this wire (No. 19B.W.G., or 0-98 millimetre 

 diameter) was very great; in the hard state the breaking stress of some specimens ranges from 107 to 

 110 tons per sq. inch, with a scarcely perceptible elongation (about 1 percent.); in the soft state the 

 tenacity was about half the foregoing.— Proc. Royal Bublin Society, 1886 and 1889. W. F. B. 



