Barrett — On the Physical Properties of Manganese 8 feel. 365 



of 280 lbs., or one-eighth of a ton, which corresponds to the 

 enormous breaking stress of 110*2 tons per square inch. A second 

 experiment gave a breaking stress of 278 lbs., which corresponds to 

 109*4 tons per square inch, with an elongation of but little over 

 1 per cent. ; the ordinary steel wire I tried elongated double this 

 amount. Experiments on the breaking strain of bars of this steel 

 have also been made by Mr. Barnaby, the Admiralty inspector in 

 Sheffield, who found that the specimen of manganese steel he tried 

 bore a strain of 67 tons per square inch, with the extraordinary 

 amount of 44 per cent, elongation before breaking. 



High as is this figure, the number I obtained for the wire was 

 far higher, and in fact was so remarkably high that I was anxious 

 for an independent determination with another dynamometer. 

 Mr. H. A. Ivatt, the Locomotive Engineer of the Great Southern 

 and "Western Railway Works at Inchicore, kindly undertook this 

 for me, as in their works a new and very accurate dynamometer 

 has recently been erected. Mr. Ivatt found my figure was per- 

 fectly correct, and sends me the following statement : — 



Gr. S. & ~W. E. — Locomotive Department, Inchicore "Works, Dublin. 



Owing to the extremely brittle nature of the metal, the elongation could not be 



detected. 



(Signed), 



H. A. Ivatt, Locomotive Engineer. 



Tested by W. C. Irwin. 



Mr. Ivatt also tried a specimen of thicker wire, No. 13 gauge ; 

 but I had previously spoilt this specimen by testing the effect of 

 heating it to whiteness and quenching in cold water, which 

 rendered the wire soft. This specimen in its soft state, Mr. Ivatt 

 found, had a breaking stress of 47*4 tons per square inch, nearly 



