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The Dortmund-Ems Canal, destined to connect the heart of German industry with the sea, was formally dedicated on April 1, and partially opened to commerce. After its completion, German coal will be transported to the harbors of the Ems at the same cost as the English coal which has hitherto forced back the treasures of our soil; our black diamonds will then be sold in the markets of the world, and the Kaiser Wilhelm Canal will enable the western part of the empire to exchange its coal and iron for the grain and wood of the East.
Many difficulties were encountered in cutting the canal, owing partly to the vast network of railroads in the coal region of Westphalia, but chiefly due to the insufficiency of moisture in the highlands, the latter not containing enough water to supply the many necessary sluices, at which it could be easily foreseen considerable traffic would occur.
[Illustration: The lock of the Dortmund-ems canal at Henrichenburg.]
For the modern engineer there are, however, no insurmountable obstacles. Instead of a line of ordinary locks, a single structure was 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.