d 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.

I cannot leave this interesting spot without an attempt to describe
the beautiful scene. A little to the right, the river widens into a
sort of bay, with several fine islands covered with wood; in front,
across the stream, as far as the eye can reach, are the forests of New
Hampshire, with occasional headlands of greensward. In the autumn, it
has exactly the appearance of a gigantic flower-garden--the trees
being of every imaginable colour. 'Ah!' said my friend, 'this is an
interesting spot: it was the favourite residence and hunting-ground of
the Chippewas. The Indians, like your monks of old in Europe, always
chose the most beautiful and picturesque sites for their dwellings;
but they have retired before the advance of a civilisation they could
not share or appreciate.' Talking in this way, as we returned, he
called my attention to a singular phenomenon in the river. At some
remote period there was, and it remains to the present moment, a rock
standing in the middle of the stream, about twelve feet in diameter at
the top, of an irregular form, and of the hardest granite. By the
action of the water, a mass of granite had been thrown on the top,
where it lodged. At high-w