384 Mr. Mallet on the Physical Conditions 



powder, with a ball, in the coldest weather of the past winter, and this under the disadvan- 

 tage of being secured firmly down, and not in a carriage where it could recoil. It occurs 

 to us to mention, that the bands which we made for the other gun, and which held it 

 together for more than a year past, were made from the same kind of iron as that of the 

 exploded gun.' 



"Although the information contained in the answers of Messrs. Ward and Co. rests 

 on voluntary testimony, yet the Committee place the fullest confidence in its accuracy, so 

 far as it is derived from the personal observation of these gentlemen. The answers, how- 

 ever, do not state distinctly the process of manufacturing the iron of which the principal 

 part of the gun was made ; and, on this point, the Committee have since received infor- 

 mation, also entitled to credit, that, at the forges mentioned by Messrs. Ward and Co., 

 the iron is formed directly from the ore, and without piling. Although iron, thus pre- 

 pared, is called, by some, a good ' merchantable article,' the Committee consider it of an 

 inferior quality for purposes where great strength is required. 



" 111.— Examinations relative to the Homogeneity of the Metal, the Welding, l^c. — In 

 order to a preliminary examination of the quality of the material, pieces from different 

 parts of the large fragment were broken off, and the fresh fracture exhibited by these care- 

 fully inspected. The surfaces of these pieces were found to vary from a fine granular to 

 a coarse crystalline texture ; and, in one specimen, the face of a crystal was exhibited, 

 three-fourtbs of an inch long, and half an inch wide. The faces of the crystals were not 

 in the general plane of the fracture, but in various planes ; and the comparison of all the 

 pieces fully showed great want of homogeneity in different parts of the gun. 



" It may, however, be proper to remark in this place, that the Committee were con- 

 vinced, from their own experiments during the course of this investigation, that the 

 difference of the appearance of the fracture of different pieces of iron depends very much 

 on the manner in which the breaking has been produced. In two fractures made in the 

 same bar, — the one by indenting with a chisel, and then breaking across an anvil ; and 

 the other by a gradually increasing pull, — the latter exhibited a fibrous structure, without 

 the appearance of a single crystal; while the other was pronounced, by a workman, to be 

 the fracture of a piece of inferior crystalline iron. It also appears, from the experiments 

 of the Committee, that although the fibrous fracture indicates a considerable degree of 

 ductility, it can, by no means, be relied on as an indication of the tenacity of the metal. 

 In one case, two pieces of remarkably soft and pliable iron, which exhibited a perfectly 

 fibrous texture when pulled apart, were found to possess about four-fifths of the tenacity 

 (i.e. ultimate cohesion) of a piece of iron which exhibited, under the same circumstances, 

 a granular texture. 



" The Committee, however, are convinced, that when the fractures are produced in 

 the same manner as by means of a sudden transverse force, the appearance of the surfaces 



