nal comes along the Irwell, and the stone aqueduct must be turned into
a swing bridge, or how is any ship to pass?

'Very well,' said the owners of the Bridgewater Canal, 'but you must not
let much of our water be lost, for we have little to spare.'

And this is how Mr. Leader Williams, the engineer, got over the
difficulty. He built an island in the middle of the Ship Canal for the
iron bridge to turn upon, leaving the two ends free. The bridge itself
he made in the form of a long tank, nineteen feet wide and seven feet
deep, the two ends being hinged so that they would open and close like
doors. Strengthening iron girders, rising to a height of some twenty
feet, form the sides of the bridge, while cross-girders close in the
top. The two ends of the canal proper where it reaches the entrance to
the bridge, are also provided with watertight doors. When the bridge is
in position there is a narrow gap between its two ends and the canal.
This is filled up and made watertight by a ponderous wedge, weighing
twelve tons and shaped like a U, its sides and lower part thus
corresponding in outline with those of the tank and canal. The wedge is
further padded on each side with indiarubber which, when squeezed into
place, effectually prevents any leakage. As soon as a ship is signalled
on the Manchester canal, the doors at each end of the tank-bridge are
closed, together with those at the ends of the canal. Then the U wedge
is lifted from between them, and the bridge (weighing, with the water it
contains, sixteen hundred tons) is swung round on its island pivot till
the channels are open on either side. The ship passes by and the bridge
is swung back to its original position. The towing-path (for all craft
on the Duke of Bridgewater's canal are drawn by horses) is carried
across the bridge on an iron shelf, nine feet above the water.

Beyond Barton the Salford docks are reached, and after passing one more
lock, we sail triumphantly into the magnificent docks of Manchester to
which this thread of silver leads.

[Illustration: Barton Swing Bridge and Aqueduct. A huge Crane at Work.]

[Illustration: The Barton Aqueduct. Coming through the Aqueduct.]

When first the canal was opened Manchester seemed to be taken by
surprise, and hardly knew how to perform the part of a seaport; but that
is all changed now. The docks are growing fast, and only in 1905 their
Majesties the King and Queen opened a new dock two thousand seven
hundred