Experiments on two varieties of Iron. 97 



common twisted auger, twice round, in the length just speci- 

 fied. The edges of the spiral were now exactly 7 inches long. 

 Hence the elongation of the exterior fibres on the edges was 



7-5.4 , , . 



— ^-"2— =29.6 per cent. It is proper to state, that this experiment 



was made after annealing the bar and cooling it ofi" in dry ashes. 

 In attempting to carry the torsion beyond this extent, the bar was 

 twisted off" at the jaws of the vice, in which the operation was 

 performed. 



Having thus proved that this iron is not, under any circum- 

 stances, cold shorty I caused the bar, If inches wide and .6 inch 

 thick, to be heated to a fair working red heat, and in that state 

 bent flatwise over the corner of an anvil, and a right angle exte- 

 rior and interior to be formed, f th of an inch from the end. The 

 exterior angle remained perfectly sound. On the interior, a thin 

 scale only of metal appeared to be corrugated and partly detached 

 from the rest of the mass, owing probably to a defect in weld- 

 ing, but not the least sign of a tendency to fracture was discov- 

 ered. 



Another portion of the same bar was heated as before, and 3 

 inches of it bent over and hammered flat upon the face of the ad- 

 jacent part. Complaints are made by workmen, that much of 

 the iron which they employ will not sustain either of the two 

 preceding operations. They were, however, borne by the iron 

 mider trial without evincing any weakness or undue distortion of 

 parts. A slight splintering only, similar to that just mentioned, 

 and on the same side of the bar, was seen in the last case. 



A third test of the quality of the iron when hot, was aflibrded 

 by heating about three inches near the end of the bar and driving 

 a steel punch four fifths of an inch in diameter quite through it. 

 This was done without splitting or cracking it at the edges, as is 

 too often done in making screw nuts. Machinists are well aware 

 of the importance of a good material for the formation of screw 

 bolts and nuts. 



The foregoing trials having, as was conceived, fully established 

 the freedom of this iron from the defects known either as hot 

 shortness or cold shortness, and its softness and malleability being 

 amply tested by the cutting and hammering incident to these ex- 

 periments, the next step was to determine the absolute force of 

 cohesion, together with the extensibility, when subjected to lon- 



Vol. xxxTi, No. 1.— Jan .-April, 1839. 13 



