Page:Miscellaneous Papers on Mechanical Subjects.djvu/97

 which it is capable of giving are required, a proportionally greater strain will be put upon the piece on account of the elongated form of the shot, and more strength is therefore required.

The mode of making large iron guns, by casting them in solid masses (as at present), is highly objectionable, and is certainly not suitable for bearing the full strain of a rifled gun. It is well known that if iron be cast in large masses, great irregularities will be produced in the metal during the process of cooling; and, beyond a certain limit, little or no increase of strength is gained by increasing its thickness.

Improved modes of construction can, however, be adopted, which will admit of the gun being loaded at the breech when required, and will give all the strength necessary for as large a charge of powder as can be consumed with the projectile intended for the piece. It is clear that every gun should have that amount of strength as a minimum standard.

In the construction of rifle cannon many things have to be considered in relation, and often in antagonism to each other, as the weight and length of the piece,—the diameter and weight of the projectile, the charge, the amount of rifling turn, and it sometimes happens that an advantage in one respect can only be gained by submitting to disadvantage in another.