A battery is ordinarily composed of six pieces, two of them being howitzers. The lighter batteries would, in our service, be formed of six-pounder guns and twelve-pounder howitzers; and the heavier of twelve-pounder guns and twenty-four-pounder howitzers. These heavy batteries would usually form the reserve. Each piece being attended by its caisson, this formation would give twelve carriages to each battery, six for the guns and six for the caissons. The extra caissons form a part of the reserve, and move with the train. In some foreign services a battery is composed of eight pieces with their caissons. This arm admits of three formations--_in column, in battle_, and _in battery_. In column it ordinarily moves by sections of two pieces, each piece being followed or preceded by its caisson. Columns of half-batteries are sometimes formed, and also columns of single pieces; but the latter ought never to be employed except in cases of necessity in passing a narrow defile, and at a distance from the enemy. In order of battle, the pieces are drawn up in line, their caissons forming a second line, at the distance of a few paces. When in order of battery, the pieces are formed in the same way as for battle, except that the guns are directed towards the enemy and prepared for firing. The movements and manoeuvres of foot artillery correspond with those of infantry, and of mounted artillery with those of cavalry, a battery being regarded as a battalion or squadron, of which the pieces form the platoons. Mounted batteries can seldom move with greater rapidity than the trot, except in cases of emergency, and even then the gallop can be kept up only for a very short time; but this is of no great importance, as the batteries never accompany cavalry in the charge. The French and German writers discuss artillery as employed in battle, under two distinct heads--1st, as an arm of preparation, and 2d, as an arm of succor. I. As an arm of preparation it serves, 1st, to protect the deploying of the other troops; 2d, to disorganize the enemy's masses, and to facilitate the action of infantry and cavalry, by weakening the intended points of attack; 3d, to force an enemy to evacuate a position by overthrowing obstacles with which he has covered himself; 4th, to keep up the action till the other troops can be prepared to strike the decisive blow.