PRO

420

PRO

included, is equally broad with the fore-part of the gun-carriage,and about four limes the length ; the fore-part of the slicle-carriqgeis fixed by hinge-bolts I, to the quick-work of the ship below theport, the end lying over the fill, close to the outside-plank, andthe groove reaching to the fore-end; the gudgeon of the gun-carriage, and consequently the trunnions of the gun, are over thefill of the port when the gun is run out; and the port is made ofsuch breadth, with its sides bevelled off within board, that the gunand carriage may range from bow to quarter. The slide-carriageis supported from the deck at the hinder end, by a wedge K, orstep-stool; which being altered at pleasure, and the fore-end turn-ing upon the hinge-bolts, the carriage can be constantly kept uponan horizontal plane, for the more easy and quick working of thegun when the ship lies along. Rifled barrels, till very lately, onlytook place in muskets. But in 1774, Dr. Lind, and CaptainAlexander Blair of the G9th regiment of foot, invented a speciesof rifled field-pieces. They are made of cast-iron; and are notbored like the common pieces, but have the rifles moulded on thecore, after which they are cleaned out, and finished with proper in-struments. Guns ot this construction, which are intended for thefield, ought never to be made to carry a ball of above one or twopounds weight at most; a leaden bullet of that weight being suffi-cient to destroy either man or horse. A pound-gun, of this con-struction, of good metal, need not weigh above 100 pounds, norit's carriage above 100 pounds more. It can therefore be easilytransported from place to place, by a few men; and a couple ofgood horses may transport six of these guns and their carriages, ifput into a cart. The length of the gun, (fig. 9,) being divided intoseven equal parts, the length of the first reinforce AB is two ofthese parts; the second BC, one and fifteen-sixteenths of the dia-meter of the caliber; tbe chase CD, four wanting fifteen-sixteenthsof the diameter of the caliber. The distance from the hind-part ofthe base-ring A to the beginning of the bore, is one caliber, andthree-sixteenths of a caliber. The trunnions TT are each a cali-ber in breadth, and the same in length ; their centres are placedthree-sevenths of the gun’s length from the hind-part of the base-ring, in such a manner that the axis of the trunnions passes throughthe centre-line of the bore, which prevents the gun from kicking,and breaking its carriage. The length of the cascable k one cali-ber, and thirteen-sixteenths of a caliber. The caliber of the gunbeing divided into sixteen equal parts:

The thickness of metal at the base-ring A from the

bore, is... 18-5

At the end of the first reinforce-ring B. 17

At the same place, for the beginning of the second rein-force. 17

At the end of the second reinforce C. 13

At the same place, for the beginning of the chase c . 13-75

At the end of the chase or muzzle, the mouldings «D

excluded. g

At the swelling of the muzzle b . \2

At the muzzle-fillet c . 9-5

At the extreme moulding D... g

Base-ling... 5-5

Ogee next the base-ring d . 5-5

The astragal or half-round... 4-75

Its fillet. 1

Total astragal and fillets at the ventfield e . 4

P'irst reinforce-ring B. 4 3

Second reinforce-ring C. 3-5

Its ogee... 3

Its astragal.;.;. ] y

And its fillet... ]

The muzzle-astragal, and fillet a . 4

Breadth ot.the fillet at the base-ring. 1

Distance of the fillet at the button from the fillet at the

base-ling..... 5

Breadth of the fillet at the button. 1

Diameter of the fillet at the button. 18

Distance of the centre of the button from its fillet. 12

Diameter of the button F....]g

Diameter of its neck...10‘3

I he vent should be placed about half an inch from the hot tom’ofthe chamber or bore. The rifles make onespifal tin'll in the lengthof the bore ; but go no nearer to the breech, in their full size, than

two calibers; and then terminate with a gentle slope in half a cali-ber more, so as not to prevent the cartridge with the powder frombeing easily sent home to the bottom of the gun, which w ouldotherwise constantly happen with the flannel-cartridges, and evensometimes with paper ones, if not made to enter very loosely.The shape of the rifles is semicircular, their breadth being equal tothe diameter, which is three-sixteenths of a caliber, and their depthequal to the semidiameter, or 15-sixteenths of a caliber. To hitthe mark with greater certainty than can be done in the commonrandom method, these guns are furnished with a sector, the prin-cipal parts of which are, 1. The limb, which is divided in such amanner as to shew’elevations to 15 o or20°. The length of the ra-dius is five inches and an half, and its nonius is so divided as toshew minutes of a degree. 2 . The telescope, AB, (fig. 18,) anachromatic refractor, is seven inches in length (such as is used onHadley’s quadrants, that are fitted for taking distances of the moonfrom the sun or stars, in order to obtain the longitude at sea), havingcross-hairs in it. 3. The parallel c.ylindric bar, CD, is -f s of aninchin diameter, having two rectangular ends EF, each half aninch square and an inch long. On one side of the end next thelimb of the sector, is a mark corresponding to a similar one in thehinder cock of the gun, with which it must always coincide whenplaced on the gun. The length of the parallel bar, together withits ends, is seven inches. This bar is fixed to the sector by meansof two hollow cylinders, G,'H, which allow the sector amotionround the bar. There is a fingerscrew, a, upon the hollow cy-linder G, which is slit, in order to tighten it at pleasure upon thebar. 4. The circular level I, (fig. 18, 19,) for setting the planeof the sector always perpendicular when placed upon the gun, is| of an inch in diameter. There is a small screw, a, to adjust thelevel at right angles to the plane of the sector. 5. Thu finger-screw,b, for fixing the index of the sector at any particular degree of ele-vation proposed. The line of collimation (that is, the line of vi-sion cut by the intersecting point of the two cross-hairs in the tele-scope) must be adjusted truly parallel to the bar of the sector whenat 0 degrees. This is done by placing the sector so that the verti-cal hair may exactly cover some very distant perpendicular line.If it again covers it when the sector is inverted, by turning it halfround upon the bar, which has all the while been kept steady andfirm, that hair is correct; if not, correct half tin: error by meansof the small screws, ode, (fig. 18, and 20,) at the eye-, nd of thetelescope, and the other half by moving the bar; place it again tocover the perpendicular line, and repeat the above operation tillthe hair covers it in both positions of the sector. Then turn thesector, till the horizontal hair cover the same perpendicular line;and turning the sector half round on its bar, correct it, il wrong,in the same manner as you did the vertical hair. Of the four smallscrews at the eye-end of the telescope, those at the right and left-hand move whatever hair is vertical, and those at top or under-neath move whatever hair is horizontal. On the side of the gunupon the first reinforce, are cast two knobs, F, (fig. 9, ami 21,)having their middle part distant from each other six inches, forfixing on the brass-cocks, A, (fig. 21 and 16,) which receive the rec-tangular ends of the parallel cylindric bar of the sector, when plac-ed on the gun. The next adjustment is to make the parallel bar,and line of collimation of the telescope, when set at 0 degrees, pa-rallel to the bore of the gun, and consequently to the direc-tion of the shot. The gun being loaded, the cartridge prick-ed, and the gun primed, place the sector in the cocks of (hegun ; and having first set the sector to what elevation youjudge necessary, bring the intersection of the cross-hairs in thetelescope upon the centre of the mark, the limb of the sector beingset vertical by means of the circular level, and then take off thesector without moving the gun. Fire the gun : and if the bullethits any where in the perpendicular line, passing through the cen-tre of the mark, the line of collimation of the telescope and direc-tion of the shot agree. But if it hit to the right of the mark somuch do they differ. In order to correct which, bring the gun in-to the same position it was in before firing, and secure it there.I he,11 file away as much of the forecock, on (beside next the gun,as will let the intersection of the cross-hair fall somewhere on theline passing perpendicularly through the point where Hie shot fell;and it is then adjusted in that position, so much being filed off (heside of the coVik at u, (fig. 21, and 17,) as will allow the side h to liescrewed closer, that the ends of the parallel bar may have no shake

in