e structure. Two and a half million feet of lumber were used in
building the forms.

Usable dimensions of the lock are 640 feet long, 75 feet wide, and 30
feet (at minimum low water of the river) deep.

The top of the lock is 20 feet above the natural ground surface and 6
feet above the highest stage of the Mississippi River on record. To the
top the ground will be sloped on a 150-foot series of terraces. This
will brace the walls against the pressure of water within the monolith.
It will be developed to a beautiful park. Heavy anchor-columns of
concrete will hold the walls against the pressure of these artificial
hills when the lock is empty.

Traffic crosses the canal here by a steel bascule bridge 65 feet wide,
with two railroad and two street car tracks, two vehicle roadways, and
two ways for pedestrians. Concrete viaducts lead to the bridge.

Gas and water mains, sewer pipes and telephone, telegraph and electric
wires pass under the lock in conduits cast in the living concrete.

Water is admitted into and drained from the lock by culverts cast in
the base. These are 8 by 10 feet, narrowing at the opening to 8 by 8
feet, and closed by 8 sluice gates, each operated by a 52-horsepower
electric motor. It will be possible to fill or empty the lock in ten
minutes.

There are five sets of gates to the lock. They are built of steel
plates and rolled shapes, four and a half feet thick and weighing 200
tons each. And there is an emergency dam weighing 720 tons, which in
case of necessity can be used as a gate.

Four pairs of the gates are of 55-foot size; one of 42-foot. Each gate
is operated by a 52-horsepower electric motor. When open, the gates fit
flush into the walls of the locks.

In the emergency dam is the refinement of precaution--designed as it
was to save the city from overflow in the remote event of the lock
gates failing to work during high water, and to insure the
uninterrupted operation of the lock in normal times, if the gates
should be sprung by a ship, or otherwise put out of commission.

This dam consists of eight girders or sections, 80 feet long, 3 feet
wide and 6 feet high. They weigh 90 tons each. They are kept on a
platform near the river end of the lock. Nearby is the crane with a
300-horsepower motor, that picks up these girders and drops them into
the slots in the walls of the lock. To set this emergency dam is the
work of an hour.

A ship passing through the lock will not proceed under