98 Experiments on two varieties of Iron, 



gitudinal strain, and the interior structure of the metal under va- 

 rious circumstances, including that of welding in the ordinary 

 way. 



For this purpose five bars were drawn out and prepared from 

 the specimen already described, numbered I, II, III, IV, and IX, 

 each about nine or ten inches long, one inch wide, and a fifth of 

 an inch thick. 



No. I, after being reduced to a nearly uniform size throughout 

 its length, was annealed at a red heat and allowed to cool slowly 

 in the air. 



No. II, was hammer-hardened, or beaten with moderate force 

 throughout its length until it had been for several minutes black, 

 the hammer being occasionally moistened during the process. 



No III, was forged out and hammered till it was only visibly 

 red in day light, being left at about the temperature at which 

 workmen cease their operations on many of the articles which 

 they produce. 



No. IV, after being brought to uniform size, was upset for about 

 three inches in the middle, and was then annealed and cooled 

 slowly. 



No. IX, was drawn out, cut in two in the middle and welded 

 together. This sample was only six and a half inches long. 



All these bars were then carefully gauged, both in breadth and 

 thickness at every inch of their lengths, before commencing the 

 trials of tenacity. The machine employed in testing them was 

 the same which had been used in experiments made at the re- 

 quest of the Treasury Department on the strength of materials for 

 Steam boilers, and for a description of which the reader is re- 

 ferred to the report on that subject.* 



The following table will be understood without any other re- 

 mark than that the breaking iveights, in the fifth column, are cor- 

 rected for the friction of the machine. The specific gravities of 

 several of the fragments of each bar after it had been broken up, 

 are given under the head of observations, and may serve as well 

 to illustrate the general character of the iron in this respect, as to 

 indicate the effect of the several methods of preparation on the 

 density of iron. 



* See also, Journal of the Franklin Institute, Vol. sis, p. 84. 



