her end of a
chain hung over large pulleys above. As one caisson descended the other
rose, and the apparatus was worked by putting about a ton more water in
the descending caisson than in the ascending one. At Anderton a lift was
erected in 1875 to connect the Weaver navigation with the Trent and
Mersey canal, which at that point is 50 ft. higher than the river. The
lift is a double one, and can deal with barges up to 100 tons. The
change is made while the vessels are floating in 5 ft. of water
contained in a wrought iron caisson, 75 ft. long and 15-1/2 ft. wide. An
hydraulic ram 3 ft. in diameter supports each caisson, the bottom of
which is strengthened so as to transfer the weight to the side girders.
The descending caisson falls owing to being filled with 6 in. greater
depth of water than the ascending one, the weight on the rams (240 tons)
being otherwise constant, since the barge displaces its own weight of
water; an hydraulic accumulator is used to overcome the loss of weight
in the descending caisson when it begins to be immersed in the lower
level of the river. The two presses in which the rams work are connected
by a 5-in. pipe, so that the descent of one caisson effects the raising
of the other. A similar lift, completed in 1888 at Fontinettes on the
Neuffosse canal in France, can accommodate vessels of 250 tons, a total
weight of 785 tons being lifted 43 ft.; and a still larger example on
the Canal du Centre at La Louviere in Belgium has a rise of 50 ft., with
caissons that will admit vessels up to 400 tons, the total weight lifted
amounting to over 1000 tons. This lift, with three others of the same
character, overcomes the rise of 217 ft., which occurs in this canal in
the course of 4-1/3 m.

Animal power.

_Haulage._--The horse or mule walking along a tow-path and drawing or
"tracking" a boat or barge by means of a towing rope, still remains the
typical method of conducting traffic on the smaller canals; on
ship-canals vessels proceed under their own steam or are aided by tugs.
Horse traction is very slow. The maximum speed on a narrow canal is
about 3-1/2 m. an hour, and the average speed, which, of course, depends
largely on the number of locks to be passed through, very much less. It
has been calculated that in England on the average one horse hauls one
narrow canal boat about 2 m. an hour loaded or 3 m. empty, or two narrow
canal boats 1-1/2 m. loaded and 2-1/2 m. empty. Efforts have
accordingly