256 



GEOLOGY OF THE SECOND DISTRICT. 



Fig. 1. 



Extract from a Report, hy Prof. W. R. John.son, of CTperiments on the iron manufactured 

 at the village of Mclntyre, Essex county, New-York. 



To ascertain the toughness and ductility of thi.s iron, when cold, I caused the bar to be bent 

 at a temperature of 50°, at a part where llie breadtii was I • 295 inclics, and the thickness 

 0"59 inch. This bend was made flatwise, and continued until 

 the corresponding faces on the inside, about one incli from the 

 middle of the inner curve, were 0-4 of an inch apart, and the 

 widest part of the opening only 0"45 of an inch. The altera- 

 tion in the form of the bar appeared to be limited to this por- 

 tion. On measuring along the interior and exterior edges of 

 this curve, the former was found to be 2' 15, and the latter 

 3" 8 inclics ; manifesting a difference in the length of the inner 

 and outer fibres, of 1 • 65 inches in a length of about 2^, the 

 original extent of the bent portion (see fig. 1). By this trial, 

 the whole form of the cross section of a bar is changed, and 

 instead of straight lines, exhibits only curves. In the present 



case, the parallelogram fig. 2 was converted into the form of fig. 3, the largest curve being on 

 the inside of the bend. 



This change of figure and displacement of parts were borne without exhibiting any signs of 

 rupture, until the curvature above stated had been attained, when a few cracks began to appear 

 on the exterior part of the curve. 



The next test to which this iron was subjected, was to heat a portion of the bar to redness, 

 quench it in cold water, and then bend the same portion cold, in the manner already described. 

 No difference of result was obtained, except a greater facility in producing it. A few slight 

 surface cracks were seen near the close of the operation. ■■ 



A third trial of a similar kind, on a bar annealed and cooled in dry ashes, resulted like the 

 preceding, but exhibited rather more cracks on the exterior surface of the bend than either of 

 the foregoing. 



Another trial of the toughness of this iron, when cold, was made by drawing out a barO'7 

 of an inch wide, 0'18 inch tliick, and 5'4 inches long, and twisting it cold in the manner of 

 a common twisted auger, twice round in the length just specified. The edges of the spiral 

 were now exactly seven inches long. Hence, the elongation of the exterior fibres on the 



edges was — ^r^^ — ■ — 29 '6 per cent. It is proper to state, that this experiment was made 



