Motion compound, (mouvement composé, Fr.) is the motion of one body impelled by two different powers.
Motion of projection, (mouvement de projection, Fr.) that by which bodies are impelled through the air, or through any other fluid. A shell which is forced out of a mortar by means of inflammable gunpowder has a motion of projection.
Motion of vibration, or vibrating motion, (mouvement de vibration, Fr.) is the circular motion of a body, which is generally round or spherical.
Motion of undulation, or undulating motion, (mouvement d’ondulation, Fr.) a circular motion which is perceptible in water, when any hard substance is thrown into it.
Motions of an enemy, (mouvemens d’un ennemi, Fr.) The different marches, positions, &c. which an enemy takes are so called.
To watch the MOTIONS of an enemy, (guétter un ennemi, Fr.) To keep a good look out by means of a regular communication between head-quarters, and the outposts of your army. On a large scale, the business of an army of observation is chiefly confined to this species of service. On a more limited one, the duty is frequently entrusted to partisans and light troops.
Motion of a bomb or ball. The progress which a bomb or ball makes through the air may be said to consist of three sorts, after it has been delivered out of the mortar, or emitted from a gun or musquet. These are:—
The violent MOTION, or first explosion, when the powder has worked its effect upon the ball, so far as the bomb or ball may be supposed to move in a right line.
The mixed MOTION, or yielding impulse, when the natural weight of the bomb or ball begins to overcome the force which was given by the gunpowder.
The natural MOTION, or exhaustion of the first impulse. This occurs when the bomb or ball is falling to the ground.