If the first line makes a flank or central change of position, the second must make a change also on such point as will bring it into its relative situation.
The march of the second line in front, is regulated by its own division or battalion of direction, which moves relatively to that of the first line. In forming in line it will march upon its own points which are parallel to, and ascertained in consequence of those of the first.
When the lines break into columns to the front, the second will generally follow those of the first. When the march is to the flanks, the second line will compose a separate column, or columns. When the march is to the rear, the second line will lead in columns.
The distance betwixt the lines, may be in general supposed equal to the front of one or two battalions, and an interval.
The second lines are seldom composed of as many battalions as the first: they are often divided into distinct bodies, covering separate parts of the first line, and consequently preserving a relative parallelism and distance.
Second lines should not always remain extended, they may often be formed in column of battalions, or of greater numbers, ready to be moved to any point where their assistance is necessary.
Whenever the first line breaks, and manœuvres by its right to face to the left, or by its left to face to the right: the movements of the second line are free and unembarrassed, and it may turn round the manœuvring flank of the first line, and take its new position behind it, by extending itself parallel to that direction, how oblique soever it may be.
The central movement generally required from the second line to conform to that of the first, is equivalent to that line marching in two columns of platoons, from near the centre obliquely to the front, and from that situation forming to both flanks.
The movements of the central columns being well understood, those of the battalions of the wings, are similar in two lines.
The officer commanding the second line, must always be properly informed of the nature of the change to be made by the first, that he may readily determine his corresponding movements.