386 



Mr. Mallet on the Physical Conditions 



Committee in that city, was cut from the wall of the chamber, lengthwise of the fibre : its 

 position is shown at g, in Fig. 1. For the purpose of comparison, the same member of 

 the Committee was furnished, by Messrs. Ward and Co., with two bars of iron taken from 

 the same parcel, and supposed to be of the same quality as that used in the construction 

 of the gun. 



" The following is a Report of the experiments and observations made with these bars 

 in Boston, so far as they have an immediate bearing on the questions to which the Com- 

 mittee are restricted. It should be recollected, that they were made by one of the members 

 of the Committee, and without a knowledge of the results obtained in Philadelphia by 

 the other members. 



" 'The bar cut from the body of the gun was reduced, in a planing-machine, to the 

 size of 2 inches square, and was subjected to a transverse strain, supported at both sides 

 on knife-edges 20 inches apart, and the weight applied in the middle. The different 

 weights applied, with the deflections, and the permanent set caused thereby, were as 

 follows : — 



" ' The bar endured this strain without exhibiting any cracks, or other indications of 

 approaching rupture. One of the original bars, having the same dimensions, was tried in 

 like manner, and gave similar results. 



" ' By these trials it appears, that so far as respects the quality of stiffness, the iron has 

 undergone no change in the process of forging the gun. 



" ' To determine the tensile strength of the iron, or its power to resist being torn asun- 

 der by a force applied in the direction of the length of a bar, three specimens, taken from 

 each bar, were reduced to a suitable form for breaking by tension, in a turning-lathe, in 

 order to have the material in the same state as it existed in the bars, undisturbed by any 

 heating or hammering. The third specimen from each bar was drawn down under a 

 welding heat, at a common smith's forge. All of them were reduced, in the part where 

 the fracture would occur, to a uniform diameter of six-tenths of an inch. 



" ' The following results were obtained : — 



" ' 1. — From the original bars, representing the quality of the iron before welding the 

 gun:— 



