Congreve Rockets are of four different natures—viz., 24 pounders, 12 pounders, 6 pounders, and 3 pounders. The cases are of wrought iron, and the rockets are driven upon the same principle as Signal rockets. Congreve rockets may be used either as shot or shell-rockets, and the shell may be made to burst either at long or short ranges. Each rocket is fitted with a fuze screwed into the base of the shell; this fuze is as long as the size of the shell will admit of, so as to leave sufficient space between the end of it and the inner surface of the shell, for putting in the bursting powder, and the end of the fuze is capped to serve as a guide in the insertion of the boring-bit. There is a hole in the apex of the shell, secured by a screw metal plug, for putting in the bursting powder, and for boring, according to the different ranges at which it may be required to burst the shell.
ON FIRING ROCKETS.
If the Rocket is to be used as a Shot-rocket, the only thing to be attended to, is to take care that there is no powder in the shells, and that the plug is secured in the plug-hole. If the rocket is to be used as a shell-rocket at the longest range, the plug is to be taken out, and the shell filled, the fuze left at its full length, and the plug replaced. If at the shortest range, the fuze is to be entirely bored through, and the rocket composition bored to within an inch and a half of the top of the cone in the 24 pounder rocket, and to within one inch in the 12, 6, and 3 pounder rockets. The distances from the surface of the shell to the top of the cone, and from the surface of the shell to the end of the fuze, and also, the length of the fuze being fixed and known, the place on the boring-bit at which to screw the stopper, whether for various lengths of fuzes, or lengths of rocket composition to be left over the cone, is easily determined; these distances are marked on the brass scales for each nature of rocket, and the length of rocket composition available for boring into, and the lengths of fuze, are also set off and subdivided into tenths of an inch.
ELEVATIONS, RANGES, AND LENGTHS OF FUZE.
The 24 pounder and 12 pounder rockets are very destructive against troops from 800 to 1000 yards; against buildings, &c., from 500 to 600 yards: with 6 pounders about 300 yards, and never at a greater range than 600 or 700 yards.
The range and elevation of a 12 pounder rocket is 10 degrees of elevation for 600 yards, and 1 degree more is given for each additional 100 yards, as far as 1250 yards, the elevation for which will be 16 degrees.
The range and elevation of a 6 pounder rocket is 7¾ degrees for 400 yards, and as far as 700 yards 1 degree for each 100 yards; and from 700 to 1250 yards, half a degree increases the range about 100 yards.
24 pounders.—If the whole length of fuze is left in the shell, the rocket may be expected to burst at from 3300 to 3700 yards; elevation, 47 degrees.
If the whole of the fuze composition is bored out, and the rocket composition left entire, the shell may be expected to burst at about 2000 yards; elevation, 27 degrees.
If the rocket composition be bored to within 1·5 inch of the top of the cone, the shell may be expected to burst at about 700 yards; elevation, 17 degrees.