A very simple system of fastening has been devised for keeping the
bridge in a stationary position when raised. When it reaches the end of
its upward travel, four bolts engage with an aperture in the suspension
rod and prevent it from descending. These bolts are set in motion by
two connecting rods carried by a longitudinal shaft and maneuvered by a
lever at the end of the windlass.
At the lower part the bridge rests upon iron plates set into sills. It
is guided in its descent longitudinally by iron plates that have an
inclination which is reproduced at the extremities of the bridge
girders, and transversely by two inclined angle irons into which fit the
external edges of the bottoms of the extreme girders.
[Illustration: FIG. 2.--ELEVATION AND PLAN.]
The total weight of the bridge is, as we have said, 44,000 pounds, which
is much less than would have been that of a revolving bridge of the same
span. The maneuvering of the bridge is performed with the greatest ease
and requires about two minutes.
This system has been in operation at the market station of La Vilette
since the year 1868, and has required but insignificant repairs. We
think the adoption of it might be recommended for all cases in which a
slight difference between the level of a railroad and that of a water
course would not permit of the establishment of a revolving bridge.
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