After the ship has been made
secure by means of wedges, the frame is drawn up by chains that
wind round fixed windlasses. These apparatus are established upon a
horizontal surface 25.5 feet above low-water mark so as to give the
necessary slope, and at which terminate the tracks. They may, moreover,
be removed after the ships have been taken off, and be put down again
for launching. For 136 feet of their length the lower part of the
sliding ways is permanent, and fixed first upon rubble masonry and then
upon the earth.
Fig. 1 gives a general view of the arrangement. The eight sliding ways
of the central part are usually reserved for the largest vessels. The
two extreme ones comprise, one of them 7, and the other 6, tracks only,
and are maneuvered by means of the same windlasses as the others. A
track, FF, is laid parallel with the river, in order to facilitate,
through lorries, the loading and unloading of the traction chains. These
latter are 3/4 inch in diameter, while those that pass around the hulls
are 1 inch.
The motive power is furnished by a 10 H.P. steam engine, which serves at
the same time for actuating the machine tools employed in construction
or repairs.
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