Barrett — On the Magnetic Moment of Steel, etc. 461 



a curious combinatiou of properties. When submitted to a stretch- 

 ing force it elongates almost like copper, aud yet has a higher 

 tenacity than Siemens' steel. The specimen No. 552, to which 

 we shall refer subsequently, with 137 per cent, of manganese 

 had a breaking strain of 63 - 5 tons per sq. inch, and an elongation 

 of 45 per cent. The work done in fracturing this specimen of 

 manganese steel is, according to Professor Kennedy, quite unprece- 

 dented in any material, being upwards of double that required 

 for the best steel. The breaking strain of the No. 19 hard wire, 

 0.98 mm. dia., I found to be 110 tons per sq. inch, or 1735 x 10 4 

 grammes per sq. centim, and of the same wire annealed 49 tons 

 per sq. inch or 768 x 10 4 grammes per sq. centim. The modulus 

 of elasticity of the hard wire was found by direct stretching to be 

 16,800 kilogrammes per sq. millim, or 1680 x 10 6 grammes per 

 sq. centim, and of the annealed wire 1500 x 10 6 grammes per sq. 

 centim. The electric resistance of this specimen of the wire was 

 found to be 75 microhms per cubic centim, or upwards of 40 times 

 that of pure copper, 6 times that of pure iron, and nearly 3J times 

 that of German silver. Its increase of resistance for rise of tempera- 

 ture, or temperature co-efficient, was found to be considerably less 

 than that of pure iron, being 0*13 per cent, per degree centigrade, 

 but higher than German silver, which is only 0*04 per cent, per 

 degree centigrade. Professor Fleming and Mr. Mordey have 

 subsequently verified these results, the specimen tried by Professor 

 Fleming having a somewhat lower, but still very high, specific 

 resistance, namely 68 microhms per cubic centim. I have also 

 determined the co-efficient of expansion of manganese steel between 

 and 100° C, and find it to be 0-000015— for this range of tem- 

 perature ordinary steel is 0*0000117. All these experiments were 

 made on an alloy containing from 13 to 14 per cent, of man- 

 ganese. 1 



1 Since the foregoing was written, Professor Le Chatelier in an official report of a 

 Committee of tlie " Societe d'Encouragement pour 1' Industrie " has stated his experi- 

 ments have completely confirmed all the remarkable mechanical properties which Mr. 

 Hadfield has found in this new alloy. Tempering, he states, produces the unique 

 effect of imparting great tensile strength, increased resistance to shock, and an elonga- 

 tion of over 50 per cent, before rupture. The French Committee, therefore, suggests 

 its use in a forged and tempered state for agricultural implements, wheels, axles, &c. 

 The co-efficient of expansion for 1°C. between and 1000° C. Professor Le Chatelier 

 finds to be 0-0000245, ordinary carbon steel for the same range being much less, via 

 0-000015. 



