transportation.

On navigable streams a part of the bridge resting on one or two bateaux
should be so arranged that it can be shipped out of its place, forming a
_draw_ for the passage of river-craft. Indeed, it would be well, even
where the river is not navigable, to form a draw for the passage of
trees, and other floating bodies, sent down by the enemy against the
bridge.

An ordinary bridge-equipage of bateaux, or light pontons, for crossing a
river of from three to four hundred yards in width, and of moderate
current, will require a train of from sixty to eighty wagons.[46] Under
favorable circumstances, and with a well-instructed corps of pontoniers,
the bridge may be thrown across the river, and prepared for the passage
of an army in a few hours at most.[47] After the troops have passed
over, the bridge may be taken up, and replaced on the wagons in from a
quarter to half an hour.

[Footnote 46: The number of wagons in a ponton train will be greatly
diminished if it be found that Indian-rubber boats may be used as
supports for the bridge. The engineer department of our army are making
experiments to determine this point.]

[Footnote 47: In 1746, three bridges of bateaux were thrown across the
Po, near Placentia, each fifteen hundred feet in length, and entirely
completed in eight hours. In 1757, two bridges of bateaux were thrown
across the Rhine, at Wesel, in half an hour; again, in the same year, a
third bridge was thrown across this river near Dusseldorf, in six hours.
In 1841, Col. Birago, of the Austrian army, arrived on the bank of the
Weisgerben arm of the Danube, with his bridge-equipage, at a round trot,
and immediately began the construction of his bridge, without any
previous preparation or examination. In less than three-quarters of an
hour the bridge was completed, and three loaded four-horse wagons passed
over on a trot, followed by a column of infantry.]

The following examples will serve to illustrate the use of different
kinds of boat-bridges in military operations:--the passage of the Rhine,
in 1702, by Villars; the passage of the Dnieper and the Bog, in 1739, by
the Russians; the passage of the Danube, in 1740, by Marshal Saxe; the
passage of the Rhine, near Cologne, in 1758, by the Prince of Clermont;
the passage of the Rhine, in 1795, by Jourdan; the passage of the Rhine,
at Kehl, in 1796, by Moreau; and again the same year, at Weissenthurn,
and at Neuwied, by Jourdan; the bridges across