ON RIFLED GUNS. 



ciently instructed in its principles and use to avoid the risk, much more the certainty, of 

 failure. We have no such system. Of the principal guns now in use, some have come from 

 individual enterprise at home, while others have been imported from abroad. These guns are 

 various in pattern, and require different modes of treatment, As a system, they are wanting 

 in that degree of uniformity, and consequently in that simplicity which comes from uniformity, 

 essential to efficient concert on the part of large bodies of men of various grades of intelli- 

 gence, that must act together in their use. In the transfer of a gunner from one station to 

 another, he should never be conscious that he has changed his piece, except in its character 

 of gun, howitzer, or mortar; otherwise, just that kind of disaster which has characterized some 

 of our artillery practice during the present war must be expected. 



While the investigation hero proposed is intended to be general, and applicable to all 

 rifled guns, yet, as the object is numerical results, and as these results must vary with the 

 character of the twist, someone class of these guns must be taken as a type. Take those 

 constructed by Mr. P.areott. 



The calibres of these guns vary from two and nine-tenths to' ten inches, and the weights 

 of the missiles range from ten to three hundred pounds. As before remarked, they, like all 

 rifled guns, are subjected to three strains. The first stretches in the direction of the circum- 

 ference, the second in the direction of the length, and the third twists around the axis. The 

 object is to find the second and third in terms of the first. The first being known from 

 experiment, the latter become known. The known shape and dimensions of the guns, and the 

 strength of the material of which they are made, complete the requisite data, and the applica- 

 tion of the formulas will be eas}\ 



LAW OF THE TWIST. 



(1) — The twist is increasing, starting with nothing at or near the bottom of 

 the bore and reaching a maximum at the mouth, and determined in this wise, 

 viz: C A B D represents the development of so much of the cylindrical bore as is 

 G traversed by a single groove on a plane tangent along an element of the cylinder 

 which coincides with the groove where it begins at the bottom. A C is the 

 development of that part of the circumference, at the bottom, into which the 

 entire groove is projected; A N E is a quadrantal arc, described with C as a centre 

 and C A as a radius. The quadrant A N E is divided into any number of equal 

 parts. A B, which is the length of the groove in the direction of the axis of the 

 gun, is divided into the same number of equal parts. Lines are drawn through 

 the points of division on the quadrant, parallel to A B. and through those of A B 

 c p jl parallel to A C; where these lines meet, taken in their order from A, give points 

 in the developed groove. P M and G M are two of such lines, and M is a point on the curve 

 sought. 



EQUATION OF THE DEVELOPED GROOVE. 



">)-Draw the radius C N, and denote the angle A C N by f. Call the radius C A, r; take 

 (314) 



