Читать книгу The Ice Crop: How to Harvest, Store, Ship and Use Ice онлайн

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The center of the dam is provided with a sluiceway large enough to carry off flood waters, and, at the bottom, a pipe or a box well bedded in cement gives a current on the bottom which carries off sediment. It is also useful in taking off air and gases, which, arising from the bottom, form air bubbles in the ice. Some water should always pass over the upper sluiceway.

Dams may be formed entirely of an embankment of earth and stone. Their base should not be less than their height, with increased thickness where pressure from a current has to be resisted. Shallow dams may be formed by driving two rows of plank across the line of the dam, and filling in the inclosed space with rammed clay. Break joints in the planking, and bolt stringers along the top edges to bind them firmly together.

In Changing the Course of Streams, cut the new channel deeper than the old one, to insure the current following it. Straightening or changing the course of a stream will often improve the topography of a farm and drain wet or marsh land.