My friend gave me a very graphic description of the opening of the
works. The whole was built in a cofferdam, quite dry, and the opening
was a holiday. Every spot within sight was covered with spectators,
for whom the engineer had contrived a surprise. The works used in
keeping the water out of the reservoir, and protecting the new dam,
were undermined, and charged with gunpowder. At a given signal, the
train was fired, and in an instant the whole blew up; and when the
smoke cleared away, the fragments were floating down the Merrimac, and
the canal full of water.
On the left from the point, the egress of water is regulated by
flood-gates of a superior construction. The building crosses the
canal, and contains seven huge gates, which are raised or dropped into
their places by beautiful machinery. To each gate is attached an
immense screw, which stands perpendicularly, twenty feet long and ten
inches in diameter. At its upper end, it passes through a matrix-worm
in the centre of a large cog-wheel, lying horizontally The whole is
set in motion by the slightest turning of a handle; and here I saw the
application of the Turpin Wheel I spoke of before--no engine or
complication, but a wheel fifteen feet in diameter, fixed
horizontally, submerged in the stream, receiving the falling waters,
and thus rapidly revolving, and by a gear, giving motion to the
machinery for raising or lowering the immense gates, stopped or set
going by merely turning a stop-cock, and requiring no more force than
an ordinary water-cistern.
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