ROCKET, a cylindrical case of paste board or metal, attached to one extremity of a light wooden rod, and containing a composition which, being fired, shoots the whole of the arrangement through the air, by that principle that an unbalanced reaction from the heated gases which is sue from openings in fireworks gives them motion in the opposite direction. As sig nals between persons who were unable to communicate with each other on ac count of darkness or some other cause, rockets have long been employed. They were also used for the important service of determining the difference of longitude between two places.
The force by which a rocket ascends is similar to that by which a gun recoils when it is fired. The rod serves to guide the rocket in its flight, the common cen ter of gravity of the rocket and rod being a little below the top of the latter. The distance at which signal rockets can be seen varies between 35 and 40 miles; and the times of ascent from 7 to 10 sec onds. At the beginning of the 19th cen
tury Sir William Congreve converted the rocket into a terrible projectile of war, with ranges which no ordnance of that day could attain. Discarding the small sizes, he made 12, 18 and 32-pound roc kets which he charged with canister-shot, bullets, and other missiles. The stick for a 32-pound rocket is 18 feet in length, and the maximum range 3,500 yards. The range can be also increased by discharg ing the rocket from a cannon, with a time fuse to ignite it at the cannon's utmost range, when the rocket commences its own course. The Congreve rockets were first tried in actual service, and with fatal effect, at the attack on Copenhagen in 1807. A rocket is also a piece of wood employed to blunt the end of a lance in a tourney, to prevent it from doing hurt.
In the World War rockets were used by the different combatants as signals, but more often bombs discharging colored lights.