erected sufficient for the needs of the entire region. This lock is
situated at Henrichenburg, near Dortmund, and our illustration
pictures it with its lock-chamber half raised.

The lock, which serves to overcome a difference in level of fifty-nine
feet, raises vessels of 1,000 tons capacity with a velocity of 0.3 to
0.7 foot per second, and has been constructed after a new and
astonishingly simple system.

The lock chamber, designed for the reception of the various vessels,
is 229.60 feet in length and 28.864 feet in breadth and normally
contains 8.2 feet of water. Under the sluice in a line with the long
axis are five wells filled with water in which cylindrical floats are
placed, connected to the bottom of the chamber by means of iron
trellis-work. The floats are placed so deeply that, in their highest
position, their upper edges are always submerged; they are, moreover,
of such size that by means of their upward impulsion the chamber is
held in equilibrium. Irrespective of the small differences of pressure
which arise from the varying immersion of the framework, the lock will
in all positions be in equilibrium. Since a vessel which enters the
lock displaces a volume of water whose weight is equal to the weight
of the vessel, a constant equilibrium will always be maintained and
only a minimum force required to raise or lower the chamber. In order
to move the lock-chamber up and down and to sustain it constantly in a
horizontal position, nuts have been fixed to strong crossbeams,
through which powerful screw-rods work.

These rods are held in place by a massive framework of iron and are
turned to the left or to the right by means of a small steam engine,
placed at one side of the lock, which engine, by means of a