Lock

(lok.) [A. S. loc.] (Mech.) A contrivance for securely fastening the door of a building, the lid of a box, L.are of various forms,but the principle on which they are all constructed is the application of a lever (the key) to an interior bolt, by means of a communication from without; and the security of L. depends upon the impediments (wards) which maybe interposed betwixt this lever and the bolt, and the impediments to the movement of the bolt (tumblers, .), which are to be thrown out of action by the key. L. are known to be of great antiquity, because sculptures of what are similar to those now used in Egypt have been discovered on the great temple of Karnac, whence Denon infers they were known in Egypt about 4,000 years since. (Inland Navig.) The barrier or works of a canal, which confine the water where the change of level takes place; it is furnished with gates at each end, which separate the higher from the lower level. When a boat pa es up the canal, the lower gates are opened, and the boat pa es into the L., after which the gates are shut. A sluice, communicating with the upper part of the canal, is then opened, and the L. rapidly fills with water, elevating the boat on its surface. As soon as the L. is filled to the highest water-level, the upper gates are opened, and the boat, being now on the level of the upper part of the canal, pa es on its way. The reverse of this proce is performed when the boat is descending the canal. The amount of elevation and descent made by the L. of a canal is termed the lock age. -(Gun.) That part of a musket or fowling-piece which contains the apparatus for igniting the charge by percu ion. [s. 551]