MECHANICS AND USEFUL ARTS. 91 



eDipse, or, as it may be otherwise termed, an elliptical twist. No draw- 

 ing can well give a fair illustration of the peculiarity involved in this form 

 of bore. A knowledge of its essential features may, perhaps, be best 

 obtained by the reader, by the aid of a roll or tube of paper. Let him for 

 instance, roll up a sheet of paper, in the form of a plain cylinder, then 

 applying slight lateral pressure to the yielding tube, he will give it an elliptical 

 transverse section. Still holding the tube in this condition, a slight twist 

 must be given to it round the axial line of the bore as a center. This, then, 

 is the " Lancaster" bore, amounting to a two-grooved rifle with very wide 

 grooves. The diametrical measurement across the transverse axis of the 

 ellipse coincides with that line which in the common rifle would be compre- 

 hended between the bottoms of two opposite grooves ; while a line taken 

 across the conjugate axis, answers to the measurement of the plain surface 

 bore of the ordinary arm. Hence there are no angularities in this bore ; what 

 are, in reality, the rifle-grooves, are formed so as to sweep gradually and 

 smoothly by a symmetrical curvature into the projecting or plain surface of 

 the bore. The great object here carried out is the getting rid of all angles in 

 the bore, and the ellipse is the most convenient form for attaining this result, 

 although it is obvious that many other sections of bore might be used for a 

 similar purpose. Any of the common forms of balls may be used in cannon 

 of this class, provided the sectional figure corresponds in its bearing part to 

 the ellipse of the barrel, the cylindro-conoid being clearly the best suited for 

 this, as for smooth bores, or common rifles. Mr. Lancaster has also adopted 

 a new form of percussion explosive action, for use in his guns. He uses a 

 piece of copper tube, surrounded at its lower end with leather, molded to fit 

 the fire-aperture of the breach. The lower portion of this tube is filled with 

 gunpowder, while the external upper part is supplied with a detonating com- 

 pound. On the barrel, or plug, of the gun, is a projecting piece, standing 

 somewhat below the uncovered portion of the detonating tube, so that when 

 the hammer strikes the tube the projecting stop offers a resistance to the blow, 

 and causes an explosion of the detonating substance. Many of the Lancaster 

 guns used hi the Crimea have burst in a most destructive way ; whether 

 there is too little metal in the guns for their charge and weight of ball, or 

 whether the great tendency of the ball to go straight forward, and thus 

 wedge itself hi attempting to over-ride the very gradual curve of the rifled 

 bore, is not yet a settled point. Lond. Prac. Mechanic's Journal. 



Notwithstanding then- immense range, the Lancaster guns have been found 

 in the Crimea to have little precision hi their aim, and to be enormously ex- 

 pensive, each charge costing 20 ($100). 



IMPROVEMENTS IX THE FABRICATION OF ARMS AT THE 

 TLNTTED STATES ARMORIES. 



Within the last few years, the superiority of the rifle barrel has been made 

 greatly manifest. It has also been so modified and unproved as to adapt it to 

 the use of infantry arms. The improvements concentrated in the " Minie" 

 invention have abundantly illustrated these facts ; and seizing upon them as 



