COFFER-DAM

In Architecture, and Bridge-building, a case of piling, water-tight, fixed in the bed of a river for the purpose of laying the bottom dry for a space large enough to build the pier on. Coffer-dams are formed in various ways, either by a single inclosure or a double one, with clay or chalk rammed in between the two to prevent the water from coming through the sides. They are also made either with piles only, driven close together, and sometimes notched or dovetailed into one another; or, if the water is not very deep, by piles driven at a distance of five or six feet from each other, and grooved in the sides with boards let down between them in the grooves, lu order to build in coffer-dams a very good natural 243 COHESION. bottom of solid earth or clay is required; for though the sides be made water-tight, if the bed of the river be of a loose consistence, the water will ooze up through it in too great a quantity to permit the operations to be carried on. It is almost needle to remark that the sides must be very strong, and well braced in the inside to resist the pre ure of the ambient water. (Hutton's Tracts vol.i.) COGNIZANCE, Conmance. In Law, an acknowledgment of a fine, of taking a distre , . It also signifies the power which a court has to hear and determine a particular species of suit. [s. 256]