LOCK, a mechanical appliance used for fastening doors, chests, etc., generally opened by a key; or more broadly speaking, a lock is a bolt guarded by an obstacle, and controlled by a key. The bolt may be pivoted or rotary, but usually slides; the key generally rotates, but may act by sliding or pushing; the obsta cle, which in order to operate the bolt must be overcome by the key, may be of the warded (fixed) or of the tumbler (movable) types.
The history of the art of the locksmith is probably as old as the history of civilization, and references to it are found in the early literature of every nation. Wood was undoubtedly the first material used in construction, but the Egyptians appear to have, at an early date, employed brass and iron also. The Hebrews and Greeks used crooked keys, with ivory or wooden handles, for the purpose of bolting or unbolting doors. Some of the modern Greeks still em ploy the primitive method of closing doors from the inside by a wooden or metallic bar, attached to the door by means of leather strings or small iron chains; wood or iron keys, made in the shape of hooks, were in serted through a hole in the door and by turning lifted up the bar on the inside. The similarity of these primitive locks rendered access to the house easy and soon led to an improvement upon the method, resulting in the so-called Lacedemonian lock. This too was improved, but of the workings of this lock no description has come down to us.
Among the nations of antiquity lock-mak ing made little progress in advance of what had been done by the Egyptians. Even the Romans, who excelled the other nations of the world in iron-work, used very simple locks, resembling those of the modern Greek. The tumbler lock was next in suc cession, and was probably first invented and used by the Chinese. In this lock a lever or slide entered a notch in the bolt, which could not be moved till the tumbler was lifted by the key. The warded lock, used by the Etrus cans, was the next form of lock which came into general use. While the Roman locks belong to the same description, they were dis tinctly different. In locking and unloCking the keys did not make a complete revolution and consequently were identical with the spring locks of modern days. After the
downfall of the Roman Empire, lock-making took on an unprecedented impulse, owing to the increased danger of robbery, and human in genuity was taxed to the limit to provide means for the safe-keeping of valuables. About 1650 a fourth type of lock, the letter or dial lock, was invented by M. Regnier, director of the Music d'Artillerie at Paris, and these four types form the basis for the majority of our modern locks.
Locks were first manufactured in England during the reign of Alfred (A.D. 871-901), but no substantial improvement in their con struction was made till the latter part of the 18th century. These improved locks were the Barron, first patented in 1778, the Bramah lock, patented in 1784; these were followed in 1818 by the Chubb, and later by the American Pavautopic lock of Day and Newell. Of those then manufactured, this latter lock became the most generally used for safes because it presented the least possibility of being picked, but this lock finally succumbed to the skill of Linas Yale, Jr., an American inventor (b. 1821; d. 1868). Yale had for a number of years been interested in and had patented locks of diverse types and ingenious construction. The modern combination lock was then un known, and Yale's earlier inventions related to locks operated by keys, but great security was obtained by making the "bit' of the key changeable at will and also detachable from the handle, so that, as the latter was rotated in the lock, the former was detached and carried away from the key-hole to a remote part of the lock, and there brought into contact with the tumblers to set them in position to permit the bolt to move, the continued rota tion of the key handle then operating the bolt and returning the "bit' to the key-hole for re moval. Yale then perfected the dial lock, the improved form of which is now in universal use in America for safes and vaults, and which, as now made, is proof against picking by any methods thus far discovered.