A more substantial form may be given to the bridge by substituting for the trestles, piles, or the ordinary framed supports so much used in the newer parts of our country.
For examples of the use of bridges of this description we would refer to Caesar's celebrated bridge across the Rhine; the passage of the Scheldt in 1588 by the Spaniards; the passage of the Lech in 1631 by Gustavus Adolphus; the passage of the Danube in 1740 by Marshal Saxe; the great bridge across the Var during Napoleon's Italian campaigns; the passage of the Lech in 1800 by Lecourbe; the bridges across the Piava, the Isonso, &c., in the subsequent operations of the army in Italy; the celebrated passage of the Danube at the island of Lobau in 1809; the passage of the Agueda in 1811 by the English; the passages of the Dwina, the Moscowa, the Dneiper, the Beresina, &c., in the campaign of 1812; the repairing of the bridge near Dresden, and the passage of the Elbe in 1813, &c.
_Rafts_ formed of timbers, casks, barrels, &c., are frequently used as military bridges.

They may be made to bear almost any weight, and will answer for the passage of rivers of any depth and width, provided the current be not rapid.
Where the bridge is to be supported by rafts made of solid timbers, these timbers should be first placed in the water, to ascertain their natural position of stability, and then the larger ends cut away on the under side, so as to present the least possible resistance to the action of the current.

They are afterwards lashed together by strong rope or withe lashing, or fastened by cross-pieces let into the timbers, and held firm by bolts, or wooden pins.

These rafts are kept in place by anchors and cables placed up and down stream.

The roadway is formed in nearly the same manner as for a bridge supported on trestles.