The tracks of these planes were made of wood. Steel rails, however, had
been brought for the cars, along with the cables and the metallic parts of
the windlass; but all else was made upon the spot, including all the
wooden pulleys for transmitting motion from the wheel to the windlasses.
This excavation reached bottom at a depth of 16 meters. The second touched
bottom at about 10 meters, and gave access to a subterranean canal, which
was followed for about 20 meters. The extraction of sand was effected here
by an inclined plane moved by a Gramme machine. The generatrix had to make
1,500 revolutions, and be set in motion by an overshot wheel. As time was
wanting, it became necessary to diminish to as great a degree as possible
the number of parts to be employed in the transmission of motion, and
since there was an abundance of water, a velocity of 15 revolutions was
accepted for the wheel, which, with a total fall of 4.8 meters, had to
give a power of eight horses. A three meter pulley was placed upon the
shaft of the wheel. This was made of freshly cut wood that had been
exposed to the sun. In order to give it sufficient stability and prevent
its warping, it was placed against the wheel in such a way as to rest upon
the latter's spokes.
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