ant in the construction of the large military rocket, and will be found Sully treated in Captain Boxer's ' Treatise on Gunnery, p. 67, chapter on Rockets.
The rod serves to guide the rocket in its flight : for the common centre of gravity of the rocket and rod being a little below the top of the latter (in the one-pound rocket it is 2 feet from the upper ex tremity of the rocket, or 7 feet from the lower extremity of the rod); if wo suppose the rocket to be fired vertically upwards, and a vibration should take place about the centre of gravity by any excess of pressure on one side arising from an irregularity in the burning of the com position, the resistance of the air against the long portion of the rod below that centre, lice a force acting on the longer arm of a lever, will exceed the force by which the vibration is produced, since the latter force acts on the rocket and the upper part of the rod which constitutes the shorter arm of the lever ; and thus the vibration is checked or prevented, and the rocket is enabled to ascend steadily. But, in pro portion as the composition burns out, the common centre of gravity approaches nearer the middle of the whole length of the rocket and rod ; and the resistance of the air acting at length nearly equally above and below that centre, it can no longer counteract any inequality in the burning of the composition. Thus, in falling, the top of the rocket, or the rocket end of the rod, is downwards.
The rod performs a similar service when the rocket is impelled horizontally or obliquely ; for, while the force of projection is great enough to carry the rocket forward, and the centre of gravity of the whole is near the rocket end of the rod, the resistance of the air against the tail of the latter will nearly prevent any vibration ; but, when the centre of gravity has got near the middle of the length, the head of the rocket begins to droop, and at length the whole conies obliquely to the ground. It has happened however, from the rod being too short or too light, that the weight of the rocket, when the latter had been projected with a small elevation, has so much in curveted the line of its path before the composition has burnt out, that the rod has turned over it, and the whole bee been driven to the ground in a direction tending towards the place from whence it was projected. In signal rockets), the stick is fixed to the aide of the cylinder, a very defective arrangement, as shown by Captain Boxer in his chapter on Rockets.
Rockets whose diameters vary from 1 to 2 inches have been found to ascend vertically to the height of about 500 yards; and those whose diameters vary from 2 to 3 inches, have ascended to the height of 1200 yards. The distances at which rockets can be seen vary from 35 to 40 miles; and the times of ascent from 7 to 10 seconds. (Robin's ' Tracts,' vol. ii.) Rockets, to be employed as military projectiles, were invented by Sir William Congreve, and, in the British artillery service, a body of men, called the rocket troop, was organised expressly for their manage ment. Sir William caused the rockets to be made with strong iron cases of cylindrical forms, and terminating at the head with • paraboloid or cone ; and he attached the rod so that its axis should coincide in direction with that of the rocket, Five classes of rockets were first made, namely, 3, 6, 12, 24, and 32 pounders. The 32 pounders have now however been abolished.
The paraboloid head is hollow, and ern be used as a shell by filling it with powder, or as a shot by leaving it empty. The 12 and 24 pounders can also be used as carcasses by substituting a couical carcass head with four vents for the paraboloid head. the shell is fitted with • faze fixed in the base, that is, nearest the rocket com position. It also has a small hole at the apex, through which the bursting charge is introduced. Through this hold the boring bit is introduced when it is necessary to bore out any fuze composition for short ranges. When the ranges are very short, it is necessary to bore out seine of the rocket composition also. But this is a dangerous operation and hardly repays the trouble. The stick is screwed into the bottom of the ease, an iron disk, and round it are five yenta for the escape of the gas. In order that the direction of their flight may be more certain, military rockets are, in general, fired from tubes fixed in stands in such a manner as to be adjustable to any elevation, and raised sufficiently above the ground to keep the stick off it ; and the proper elevation, at least for the smaller rockets, is about one degree for each hundred yards in the required range. From their form they penetrate to a considerable depth when fired against timber or earth : 12 pounder rockets, after a range of 1260 yards, have been found to enter the ground obliquely as far as 22 feet. The principal inconvenience attending rocket practice Is the powerful action of the wind when it blows in a direction perpendicular, and even oblique, to the intended line of flight. The effect is very peculiar, for the wind acting on the tail, a long lever, drives the head up Into the wind. Tho rocket elionhl therefore be laid to leeward.
Rockets, being much lighter than any other kind of ordnance, and capable of being used with or without carriages, are well adapted for conveyance in mountainous countries. When fired in volleys against troupe, their effect Is likely to create much disorder; and those which act as carcasses, when fired against buildings, will almost certainly cause their destruction. Besides being employed in the siege of Copenhagen, rockets were used at the bombardment of Hushing (1809); and in 1813 the Britiah rocket-troop rendered considerable service at the battle of Leipzig. The advance of a French column against an inferior force of British troops was checked by a well directed fire of rockets at the passage of the Adour in the last mentioned year ; and it is said that the explosion of the powder magazine which in 1840 produced such disastrous effects at Acre, was caused by the fall of a rocket on the building. Rockets were used both by the French and English before Sebastopool. A rocket was invented by Mr. Hale a few years ago to be used without a stick ; the rocket was something similar to the Congreve rocket, but at the base, which is iu form like the frustum of a cone, besides a large vent hole in the axis there were five smaller holes cut obliquely through the exterior surface of the conical part. These holes, termed "tangential holes," are made with the object of giving a rotatory movement to the rocket to keep it point foremost. [Mem] The rocket was restrained by a spring in the tube till it had obtained sufficient initial velocity to prevent its drooping.
ROD. [Felten.]