THEORY AND PRACTICE

TRACT 37.

present ease, 1600 = 1500, or 16*/^- = 15; hence

2 e 15 , 2e 15* 225 e 225 l „ 4

^ b ~ 16» aDC * i ■" 16* = 256* ° r b 312 2 28 °* 9 near "

ly; that is, the charge of powder must be almost ^ of theball’s weight, to give it 1500 feet velocity. So, if the ball bean 18-pounder, the charge will be 8lb nearly. But, for a24-pounder, the charge will be almost 10].lb.

PROBLEM XIT.

To assign the Elevation necessary to give a Piece, dischargedwith a given Velocity, so as to hit an Object placed at a givenDistance.

101. This is a very useful problem in the practice of ar-tillery. For, it is obvious, and a circumstance well known,that to hit an object at some distance from the piece, it isnecessary to point the piece rather above the visual line ofthe object, on account of the descent of the shot during thetime of its flight, by its natural gravity or weight. For,were the shot discharged exactly in the line of the object, itwould be sure, in consequence of its natural descent, to falltoo low, and miss the mark. The practice is therefore toelevate and point the piece to a place as much above the ob-ject as the ball is supposed to drop in the course of its flight,so that it may just meet the object when it has arrived at theknown distance. The quantity of this elevation however isusually a very vague and uncertain degree, being taken with-out any kind of rule, and only guessed at, more or less, ac-cording to the various notions of every practitioner. It isobvious then that this way must at the best afford but a veryuncertain result, even when the shot is supposed to be pro-jected exactly in the line the piece is pointed in, which how-ever is commonly far from being the case, on account ofseveral causes of irregularity in the usual practice.

102. One of these causes is, the quantity of windage, bythe balls being mostly too small for the bore of the piece: