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. Empty
casks, and other floating bodies, may be substituted in place of logs in
the construction of rafts.

For examples of the use of rafts in the construction of military
bridges, we would refer to the passage of the Seine in 1465 by Count
Charolais; the passage of the Meuse in 1579, by Alexander Farnese; the
passage of the Vistula in 1704, the Borysthenese in 1709, and the Sound
in 1718, by Charles XII.; the passage of the Adige in 1796; the passage
of the Po in 1807; and the subsequent military operations in the Spanish
Peninsula.

Military bridges are frequently made of _boats_, and the ordinary
river-craft found in the vicinity of the intended passage. Flat-bottomed
boats are the most suitable for this purpose, but if these cannot be
obtained, keel boats will serve as a substitute. When these water-craft
are of very unequal sizes, (as is frequently the case,) two smaller
ones may be lashed together to form a single support; they can be
brought to the same level by means of stone ballast. The gunwales must
be suitably arranged for supporting the balks, or else frameworks should
be erected for this purpose from the centre of the boat. The arrangement
of the roadway, anchors, &c., is the same as before.

A _bridge-equipage_ made to follow an army in its movements in the
field, is generally composed of light skiffs or batteaux, and the
necessary timbers, planks, anchors, &c., for forming the roadway, and
keeping the bridge in its position. All these articles are constructed
especially for this purpose. All the wood-work should be of tough and
well-seasoned timber, so as to impose no unnecessary weight on the wagon
trains. The bateaux should also be made of strong and light materials.
For convenience in transportation, these boats are sometimes made with
hinges so as to fold up. The ribs are usually of oak, and the sides and
bottom of pine. Instead of plank, a covering of tin, copper,
India-rubber, &c., has sometimes been substituted. Floating supports of
this character are often made in compartments, so as to prevent their
sinking when injured by the enemy's projectiles. Indian-rubber pontons
may be folded up into a small space, and their slight weight renders
them convenient for