Barrett — On the Physical Properties of Manganese Steel. 363 



again took out the requisite ductility, and it was therefore necessary to 

 again heat the wire, and plunge it in the same manner as before. By 

 doing this each time the wire was reduced two numbers of the gauge ; 

 there was no difficulty whatever in drawing it to any desired fineness, 

 the only point necessary being that the wire must be heated sufficiently 

 hot before plunging into cold water, or the wire would be still too hard. 

 The colder the water the better the result." 



The composition of the manganese steel from which the wire 

 was drawn is slightly different from the specimen I obtained from 

 Mr. Bottomley. The analysis of the wire is as follows : — 



Iron. Manganese. Carbon. Silicon. Phos. Sulphur. 



84-96 13-75 0-85 0-25 0-10 0-09 per cent. 



I have now to lay before the Society the results of some of my 

 experiments with this material : — 



Density. — The density of the manganese steel wire, I find, is 

 7 '81, that of ordinary steel being 7*717. 



Hardness. — In its ordinary condition manganese steel is very 

 hard. It easily scratches steel that is not hard-tempered. 



Modulus of Elasticity. — The modulus of elasticity (Young's 

 Modulus) was determined by direct stretching. Experiments were 

 made with the ordinary hard manganese steel wire and with the 

 same wire annealed by sudden cooling. A length of four metres 

 was suspended from a well-constructed clamp of a new form, 

 devised and made for me by Messrs. Booth, Brothers, of Dublin, 

 and the readings were taken by an excellent cathetometer. The 

 flexure of the support under the maximum stress was carefully 

 tested and found to be inappreciable. An initial weight of 2000 

 grammes was kept on the wire, and additions were made of 10,000 up 

 to 40,000 grammes; with the maximum weight there was no set, the 

 index accurately returning to zei'o when the weights were removed. 

 Three elongations were made in each of five sets of observations, 

 the mean of the fifteen trials giving a modulus of 16,800 kilogrammes 

 per square millimetre. Another set of observations were made with 

 an initial stress of 5000 grammes ; adding to this 38 kilogrammes,. 

 on and off, the mean of three sets of observations thus made gave 

 a rather higher number, namely, 17,130 kilogrammes per square 

 millimetre. 



Mr. M'Cowan, B. Sc, the Demonstrator in Physics at the- 



