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. The amount of turn to be given must be considered with relation to the charges intended to be used and the length of the gun, but should be as quick as possible, since the extent of true steady flight, in the case of a long projectile, depends on the rotation given to it For a great range, length of gun is requisite, as it provides for the consumption of large charges of powder, but the quick turn, which is so desirable, limits the length that can be used. The best combinations and proportions can only be arrived at after careful experiment. I would observe, before concluding this paper, that it has been drawn up rather with the view of offering some reply to many inquiries, than with the intention of giving a detailed account of what has been done, or of presenting a complete treatise on the subject. NOTE. It is right to state that, from the time I first undertook, at the solicitation of the Government, to render what assistance I could in the improvement of rifled arms; I have always devoted my time and attention to them, without any remuneration whatever, even for personal expenses. The sums required have been advanced by myself; periodical accounts are sent in to the Government, and the advances have been repaid at its convenience. New York, Philadelphia, Baltimore, Pittsburgh, Buffalo, 1. Number of establishments visited. 3. Locality of Works-Beam engines. 4. River steamers for shallow waters. 6. Caloric engine. |