Experiments on two varieties of Iron, 103 



From these two comparisons we may infer that there is but 

 Httle difference between the two kinds of iron in regard to exten- 

 sibihty. Prom both modes of comparison, however, we are led 

 to notice the remarkable difference between the annealed and the 

 hammer-hardened bars. Thus by observing elongations after the 

 first trial, we have 14.5 : 5 and 15 : 6 for the ratios of extensi- 

 bility in the two kinds of iron ; and by taking the total elonga- 

 tions, we have 35 : 20.5, and 38.5 : 20 for the relations. This 

 is in accordance with what had been observed, while making ex_ 

 periments on the strength of materials for steam boilers. The 

 difference in specific gravity between the annealed and hammer- 

 hardened bars, from specimens No. 2, is 1.01 per cent. 



The iron now under consideration may be compared, in point 

 of tenacity, with American bar iron of the second class only. 



Thus from the report before cited, we find, that bar iron from 

 Missouri, by 22 experiments, bore . 47,420 lbs. per sq. in. 



That from, Mclntyre, hy 4 expts. on 

 bar, No. YII, (as above) . . 49,215 " " 



That from Tennessee, by 21 expts., 52,909 " " 



" Baltimore, by 13 " 55,213 " " 



Assuming the strength of specimen. No. 1., in each state in 

 which it was tried, as a standard, we find the following results of 

 a comparison between the two kinds of metal above examined, 

 viz. 



^T r -.xr . 53,311-47,328 ^ 



Nos. I, and V, give n^T^i — — = 11 per ct. mferiority in 



No. 2, when armealed. 



TVT XX ,x 65.713-55,657 



Nos. II, and VI, give fi^Tl3 =15.3 per ct. inferiority in 



No. 2, when hammer-hardened. 



^, ,„ ,^,„ . 58,912-49,215 



No. Ill, and V II, give ^g g-.^ =16.4 per ct. inferiority 



in No. 2, when hammered to dull red heat. 



63,142-49,311 



No. IV, and y III, give ^fioTZa =21.9 per ct. inferiority 



in No. 2, when upset and annealed. 



And the mean difference is 16. 15 per cent, in favor of No. 1, or 

 about one sixth of its total tenacity. 



