e locks upward and another flight of
three locks downward. The passage of both flights of locks is not
expected to occupy more than three hours, and ships should complete the
transit of the Isthmus--a distance of about fifty miles--within twelve
hours at most. The design of the work offers nothing that is new in
principle to engineering science. Dams, cuttings, and locks are
familiar contrivances. But they are on an immensely larger scale than
anything which has previously been attempted. The area of the lake of
impounded water will be 164 square miles, and it has been doubted
whether the damming of so large a mass of water, to a height of 85
feet, could safely be undertaken. But this portion of Central America
is apparently not liable to earthquakes. And the dam is so large as to
be a feature of the earth's surface. It is nearly half a mile broad
across its base, so that although its crest is 105 feet above sea-level
its slope is not very perceptible. Its core is formed of a mixture of
sand and clay, poured in from above by hydraulic processes. This has
set hard, and is believed to be quite impervious to water at a much
higher pressure than that to which it will be subjected. In the center
of the river valley--a mile and a half broad--across which the dam has
been flung, there very fortunately arose a low rocky hill. This is
included in the dam, and across its summit has been constructed the
escape or spill-way. During seasons of heavy rain the surplus discharge
of river water will be very heavy, and a cataract will pour over the
spill-way. But it will rush across a bed of rock, and will be unable to
erode its channel. And it will be employed to generate electrical power
which will open and shut the lock-gates and generally operate the Canal
machinery. The river Chagres will energize the Canal as well as fill
it.

The locks are gigantic constructions of concrete. Standing within them
one is impressed as by the mass of the Pyramids. The gates are hollow
structures of steel, 7 feet thick. Their lower portions are
water-tight, so that their buoyancy in the water will relieve the
stress upon the bearings which hinge them to the lock-wall. Along the
top of each lock-wall there runs an electric railway; four small
electric locomotives will be coupled to a vessel as it enters the lock
approach, and will tow it to its place. The vessel will not use its own
steam. This will lessen the risk of its getting out of hand and ramming