THE bridges which are conƒtructed by an army for paƒƒing canals, rivers, &c. being comprehended under the name of artillery, we ƒhall here give an account of what concerns them.
        Theƒe bridges are made with boats, which are placed at ƒmall diƒtances from each other, the whole width of the river, parallel to their lengths, and covered with planks, which reƒt on pieces of wood called poutrelles, or joiƒts, firmly fixed to the boats.
        There are bridges of boats of many ƒorts; ƒome are conƒtructed with copper boats, which in artillery are called pontons, and which are carried with an army upon carts or drays, made for that purpoƒe; others are conƒtructed with the common boats found on the rivers which are to be paƒƒed.
        To conƒtruct a bridge of boats, the boats are bound together with ƒtrong ropes, as is repreƒented in fig. 1, 2, of pl. XV. A-croƒs theƒe boats are laid the poutrelles, and upon them ƒtrong planks of deal, which are firmly nailed on; fir planks are preferred, becauƒe that wood is lighter and leƒs brittle than oak.
        When the river over which the bridge is to be laid is very rapid, anchors are let down from the cord or cable to which all the boats are faƒtened; theƒe anchors are firƒt caƒt into the river, and the cord is then drawn as tight as poƒƒible, that the boats may be more ƒecurely fixt; theƒe cords, or cables, are called in artillery cinquenelles, and are generally one inch and an half in diameter, and 100 fathom long.
        The boats have alƒo anchors, by means of which their ƒituation is rendered more ƒteady and ƒecure, and capable of making a ƒtronger reƒiƒtance to the tide or motion of the water.
        Fig. 1. in Plate XV. ƒhows part of a bridge of boats, which is not entirely covered with planks, that the arrangement and diƒpoƒition of the poutrelles may appear. The ƒame method is obƒerved in the bridge of boats repreƒented by fig. 2. in the ƒame plate. This bridge is only for paƒƒing ƒmall rivers.
        Fig. 3. in Plate XV. ƒhows a ponton mounted on its carriage or cart.
        M. St Remy obƒerves, in his Memoirs, that the pontons which were in uƒe before the time of M. the marquis de la Frezeliere, lieutenant-general of the artillery (which poƒt he filled with great diƒtinction) not being capable of tranƒporting twenty-four pounders over large rivers, without danger of ƒinking, becauƒe they lay ƒo near the water's edge, he contrived others longer and higher, which were capable of tranƒporting the heavieƒt pieces of artillery over any river, without danger of the like inconveniency. The principal dimenƒions of theƒe boats, according to this author, are as follow:
        Their height is 2 feet 9 inches.
        Their width 5 feet 6 inches.
        Their length 18 feet 6 inches.
        The poutrelles, which are of firr, [sic] as well as the planks with which they are covered, are 22 feet long, 4 feet and an half wide, and 5 feet thick.
        The planks are 14 feet long, 13 inches wide, and 2 inches thick.
        The diƒtance between each boat, or ponton, ought to be 9 feet.
        Beƒides the bridges already mentioned, which are moƒt common, there are yet others, called ponts volants, or flying bridges. Theƒe are ƒometimes boats, joined together by ƒtrong ropes, and frequently with chains, upon which a ƒufficient number of madriers, or planks, are diƒpoƒed, ƒo as to make a platform proper to receive cannon, and on which they may be fired, either to oppoƒe or favour the paƒƒage of a river. An epaulment is alƒo made musket proof, to cover the men who occupy this bridge, and play the cannon.
        The pont volant is alƒo ƒometimes a bridge made of one great boat, or ƒeveral leƒƒer boats, which floating, is drawn croƒs a river, by means of ƒome machines, or cords, which communicate with the oppoƒite ƒide.
        A bridge is alƒo called a pont volant, which is made over ƒmall rivulets 4 or 5 fathoms wide, and compoƒed of two bridges, laid the one on the other, in ƒuch manner as that the upper one may be thrown forward by means of cords and pullies properly diƒpoƒed in the lower. Theƒe bridges can never be large, becauƒe the weight of the upper bridge, when it runs out, or is thrown forward, wou'd, if not very ƒmall, break all its faƒtening to the under bridge, and ƒo the whole machine would be rendered uƒeleƒs ; and for this reaƒon they are never uƒed but for paƒƒing ditches, ƒoffes, or rivulets not wider than 4 or 5 fathom.
        Beƒides theƒe there is another ƒort of pont volant, made uƒe of in war on ƒeveral occaƒions, called a raft, or float. This is made of many rafters, or pieces of timber, which together form a kind of floor; theƒe are covered with planks, or ƒtrong madriers, and a certain number of empty casks are made faƒt to the ends of the rafters, the better to ƒupport the float, and whatever is placed upon it. Theƒe floats are uƒed to tranfport troops, cannon, &c. over rivers.