Congreve’s System

—A Congreve rocket is guided by a long wooden stick attached to its base. If any cause act to turn it from its proper direction, it will be opposed by resistances equal to its moment of inertia and the lateral action of the air against the stick. The effect of these resistances will be increased by placing the centre of gravity near the head of the rocket, and by increasing the surface of the stick. In signal-rockets, where the case is made of paper, the stick is attached to the side, and there is but one large vent, which is in the centre of the case. In war-rockets the stick is attached to the centre of the base, and the large central vent is replaced by several small ones near its circumference. The former arrangement is not so favorable to accuracy as the latter, inasmuch as rotation will be produced if the force of propulsion and the resistance of the air do not act in the same line.