246 Mr, F, A. Abel, on the Application of Science [April 27^ 



forgings, sufficiently perfect for conversion into cannon, were, however, 

 uniformly attended with failure, excepting in the instance of a very 

 large gun (13 in. calibre), constructed at the Mersey Company's works, 

 which hffs successfully withstood some severe trials, though even this 

 gun is not a perfectly sound forging throughout. This want of suc- 

 cess is ascribed partly to the difficulty of ensuring perfect welds 

 throughout a very large forging, and partly to a change which is 

 gradually effected in the physical structure of the metal, by its repeated 

 exposure to a high temperature, and possibly also, in some measure, by 

 its frequent subjection to powerful concussion. In large masses of 

 wrought iron, which have been built up by welding, the fibrous struc- 

 ture of the metal is always found to have passed over, more or less 

 perfectly, into a lamellar structure, and the strength of the mass thus 

 becomes very considerably diminished. 



While unsuccessful attempts to construct cannon of large masses of 

 malleable iron were still in progress, Mr. Mallet, Captain Blakeley, 

 and others, who had given the subject of the construction of cannon 

 of large size their serious attention, and had applied mathematical 

 reasoning to its elucidation, had arrived at the conclusion that the true 

 system to be followed was that of constructing cannon of several parts, 

 combined in such a manner as to render every portion of the metal 

 available in resisting, by its tenacity and elasticity, the strain exerted 

 upon the gun by the explosion of powder. The method of construction 

 proposed by those gentlemen consisted in preparing, in the first in- 

 stance, cylinders (or rings, to be afterwards braced together), and in 

 shrinking upon these, other rings, of which the internal diameter was 

 somewhat less than the external diameter of the first rings or the 

 cylinder. The latter are thus placed in a state of compression, while 

 the external rings are in a state of tension. Other rings are again 

 shrunk upon the outer ones, according to the size of the gun and the 

 strain which it has to bear. In this way, the whole of the metal com- 

 posing a heavy gun or mortar is arranged in a condition most favour- 

 able to the effectual resistance of a sudden strain applied from the 

 interior. A gun constructed on this plan, by Captain Blakeley, has 

 exhibited very great enduring powers. Two enormous mortars have 

 also been constructed by Mr. Mallet on the same principle ; and, 

 although the trials with one of these were only partially successful, 

 the correctness of the principles above referred to were in no way im- 

 pugned by the results obtained.* 



The methods adopted for the production of the beautiful rifle-gun 

 invented by Sir W. Armstrong, which is rapidly replacing the old 



♦ In referring to some photographic iUustrations of the construction of Mallet's 

 mortar, allusion was made to the very numerous applications which the photo- 

 graphic art now received to military purposes ; being not only employed as the 

 best means of recording the results of experiments, but also furnishing the most 

 ready and effective method of communicating to military authorities at a distance 

 any changes introduced in the nature and arrangements of military equipments, or 

 of giving instruction in points of drill, &c. 



