DRAW-Bridge, a bridge made after the manner of a
float, to draw up or let down, as occasions serve, be-
fore the gate of a town or castle. See BRIDGE.
A draw-bridge may be made after several different
ways; but the most common are made with plyers, twice
the length of the gate, and a foot in diameter. The
inner square is traversed with a cross, which serves for
a counterpoise; and the chains which hang from the
extremities of the plyers to lift up or let down the
bridge are of iron or brass.
In navigable rivers it is sometimes necessary to make
the middle arch of bridges with two moveable plat-
forms, to be raised occasionally, in order to let the
masts and rigging of ships pass through. This kind
of draw-bridge is represented in Plate CLXVIII. where
AB is the width of the middle arch; AL and BL,
the two piers that support the draw-bridge NO, one
of the platforms of which is raised, and the other let
down, having the beam PQ for its pleyer. To NO
are suspended two moveable braces EH, EH; which
resting on the support E, press against the bracket M,
and thereby strengthen the draw-bridge. These braces
are conducted to the rest by means of the weight S,
pulling the chain SLF.