In order that the commander of any one ship may readily ascertain and preserve his relative position in a fleet when in order of sailing, the ingenious device called the sera/ square, which was invented by Mrs) l'Iloste, may be employed. It consists in tracing upon the quarter deck a great square A B cn (diagrams Nos. 2 and 3), having two sides, A n and a c, parallel to the ship's length ; the diagonals, A c and a D, intersecting each other in E, and the line it r. s being drawn vertically over the ship's keel ; also the point it being towards the head of the ship. Now, if a ship were sailing in the direction n, close-hauled on the starboard tack, as in the cut No. '2, so that 13 n coincides with the plane of the sail, and w E (bisecting the angle II E c) with the direction in which the wind Is blowing; then, after having tacked and become close-hauled upon the port tack, since the directions of the vertical planes passing through the keel and sail make angles with the direction of the wind equal to those which they made before tacking, the line a n, that is, the line on which the ship will be sailing, will coincide with, or be parallel to, the position of 1:C in the diagram. In like manner, if a ship be sailing in the direction a st, close-hauled on the port tack, so that n o coincides with the plane of the sail, and v F. with the direction in which the wind is blowing ; then, after having tacked and become close-hauled on the starboard tack, the liue a 11, on which the ship will be sailing, will coincide with, or be parallel to, the position of E ts in the diagram.
Hence, if a fleet be in three parallel divisions, the ships sailing Armlet of each other, these in each line will be in the direction and the corresponding ships In the different divisions will be in the directions A B or D C. If the fleet sails close-hauled, and, for example, on a starboard tack as In No. 2, the ships in each line will be in a direction coincident with or parallel to a 11, and the corresponding ships in the several lines will be In a direction coincident with, or parallel to, w which is that of the wind. Again, if the fleet is in three divisions, and the ships are sailing in parallel directions not coinciding with those of the divisions; if, for example, the ships should be sailing on the port line of bearing while close-hauled on the starboani tack, as in the subjoined diagram, the ships in each lino will be in the direction of one of the diagonals of the square ; and the corresponding ships in the different divisions will be in that of the other.
The order of battle consists in the ships being drawn up in each other's wake, or in one right line with which the directions of all their keels coincide : they are usually about 50 Lathoms from one another, and are nearly close-hauled. The frigates, store-ships, &e., aro in lines parallel to that of the line-of-battle ships, and on the side opposite the enemy. A line of ships close-hauled is particularly advantageous as an order of battle both for a fleet to windward, and also for that which is to leeward of its opponent. If a windward fleet were in any other state, the enemy might, by manoeuvring, gain the weather-gage, or he might, by being able to approach as near as he pleased, compel the windward fleet to come to an action. By the " weather-gage" is meant the getting between, or the power of getting between, the enemy's fleet and the part of the horizon whence the wind blows. Rodney in 1732, and Nelson at Trafalgar, and other admirals have formed their plans of attack on this ground, because a fleet to leeward has difficulty with a fleet lying to windward, in forcing her to an engagement ; while, on the other hand, a leeward fleet, of inferior force, has a retreat more open to it. To a fleet being to leeward of an
enemy, the only hope of bringing the latter to action is in being able to outsail it, and tack across an enemy's bows ; thus getting what is called the weather-gage. In as close-hauled line, also, the sails are disposed so that the ships remain nearly stationary during the action ; on which account the lino is steadily preserved, and any ship on becoming disabled can be easily replaced by one of those which are in the reserve line.
When the ships of a fleet are in the first or second order of sailing, and it is intended to form the line of battle, it is evident that by simply hauling the wind, or by tacking [Tecsiso) or veering use), as the case may require, the ships may get into each other's wake in any proposed direction of the line. If it be intended to form the lino of battle from the third order, the ships in that wing which is already in a line, in the direction of their keels, must simply haul their wind and get into each other's wake in the proposed direction of the line ; each ship in the other wing is then brought into a position nearly at right angles to the direction of the wind, and, as those of the first wing advance, these fall successively into their wake.
When the line of battle is to be formed from the fourth or fifth order, all the ships being supposed to be close-hauled, the formation may take place upon any one of the divisions ; the ships of this division are then brought to (their motion stopped by bracing some sails HO RR to be taken aback by the wind while others are kept full), and the other ships are made to take up their proper positions in the prolongation of the line thus formed. If, for example, the fleet consists of ships sailing in three divisions close-hauled, and the line is to be formed upon the centre division, as in the subjoined diagram ; then, as soon as this squadron is brought to, the ships in the weather division bear away and steer till they get ahead of the centre, when they haul their wind ; the lee division tacks and sails on till it gets astern of the centre, and when these ships have hauled their wind the line of battle is formed. In this formation the weather division or column has been made to constitute the van, and the lee column the rear of the line ; but it is sometimes thought necessary to make the columns change places, by causing that which is on the weather side of the fleet to become the centre or rear column, or by making the centre or lee column constitute the van of the line. A like interchange of the places of the van, centre, and rear divisions is also, occasionally, made when the fleet is in the order of sailing; and various other evolutions are performed by the ships of a fleet, both while sailing and in the line of battle : the principal of these consist in the several ships tacking, or veering, in succession, and in turning to windward; and there are, besides, the series of movements which are necessary in order to restore the line of battle when disordered in consequence of a shifting of the wind. But the detals of these evolutions can be studied with advan tage only in works which are expressly written on naval tactics.