burthen, with cargo on board, are lifted out of the water for repairs,
and the heaviest bodies raised and moved, without any other expense of
human labor beyond the management of the engine.

The tubes on the Anglesea side were raised first. The presses in the
Britannia tower were each capable of raising a weight of 1250 tons; that
in the Anglesea tower, larger than the others, 1800 tons, or the whole
weight of the tube. These presses were worked by two steam engines of 40
horse power each, which forced the water into the cylinders, through a
tube half an inch in diameter. These steam engines were placed in the
Britannia and Anglesea piers. The press in the Anglesea pier is thus
described, the others being constructed in the same manner. The
hydraulic press stands on massive beams of wrought iron plates
constructed on the principle of the arch, placed in the tower above the
points where the tubes rest. The press consists of a huge cylinder, 9
feet 2 inches in length, 3 feet 6 inches outside diameter, and the ram 1
foot 8 inches in diameter, making the sides and bottom of the cylinder
11 inches thick; it was calculated that it would resist a pressure of
8000 or 9000 pounds to the square inch. The ram or piston was attached
to an exceedingly thick and heavy beam of cast iron, called the
cross-head, strengthened with bars of wrought iron. To the cross-head
were attached the huge chains that descended to the tubes far below, to
which they were secured, so that, as the ram was forced up 6 feet at
each stroke, the tube was raised the same distance. "The power of the
press is exerted on the tube by aid of chains, the links of which are 6
feet in length, bolted together in sets of eight or nine links
alternately.--The ram raises the cross-head 6 feet at each stroke, and
with it the tube, when that height is attained, a lower set of chains on
the beams grip the next set of links, and thus prevent them from
slipping down, whilst the clamps on the cross-heads are unscrewed, the