

VELOCITY. 309 



less velocity, they met with less resistance or reaction, and 

 consequently, their original elongated shape being less altered, 

 they penetrated furthest of all 



" We have here a beautiful and very instructive illustra- 

 tion of the law of action and reaction, as also of the doctrine 

 of inertia, which deserves a passing comment. Bodies in 

 motion continue in motion from the inertia of motion; 

 bodies at rest continue at rest from the inertia of rest; that 

 is, bodies which move do move, bodies at rest are at rest. This 

 is all. The idea receives colouring from two very important 

 facts. First, the progressive motion of a mass is in propor- 

 tion to the force impressed, and takes place after a lapse of 

 time from the application of the force to the atoms of the 

 body. There is needed time for the force to be diffused 

 among the atoms by atomic motion, before consentaneous or 

 progressive motion is induced. The other fact is, that in most 

 cases force in moving bodies is gradually applied. Thus a 

 ball fired horizontally over water, with a very small charge, 

 will enter the water when it first touches it ; for it can, as it 

 were, await the tardy resolution of the atoms of the water 

 into progressive motion to give it place. But when the ball 

 is fired with a full charge, it is deflected, or ricochets. Its 

 velocity is so great that it cannot transfer its force; for 

 it would take many instants for the particles of water, 

 moving with the same velocity with the bullet, to travel 

 through their atomic space, arid to induce progressive motion 

 of the column necessary to be moved for the passage of the 

 ball through the water. 



"So it is with sand, wood, iron, &c., for the destruction of 

 velocity is in all cases gradual, and the time employed will 

 depend most materially on the nature of the substance on 

 which the bullet impinges. The force which the ignited gun- 

 powder generates after having put a bullet in motion and 

 produced its full effect remains, as it were, inclosed in the 

 bullet; and the joint product of the velocity and of the 

 quantity of matter in the bullet represents the result. This 

 joint product is termed the momentum of the bullet. In 

 order, therefore, that the shot should produce the greatest 

 effect, we must move the muzzle of the piece near to the 

 object aimed at; and the nearer we move it the greater the 



