LOCK, a contrivance for securely fastening the door of a building, the lid of a box, etc. Amongst the early -Egyptians, Greeks, and Romans, locks were used, but their construction evinced little skill, and they were usually made of hard wood; in fact, they were little more than wooden bolts, requiring only the lia»d to unfasten them. The first advance upon this was a. 'remarkable one, invented by the ancientalgyptians; it contained Vie principles of the modern tuinbler-lock; but althou,gh still in use amongst the modern Egyptians and Turks, it has never, in their hands, made any advance. This lock consists of a case, which is nailed to the door; through the case plisses a lave wooden bolt, the end of which enters the staple, whilst the opposite end is left exposed. In the lower part of the bolt is a square groove, which has certain round or square holes. When the bolt is pushed home into the staple, these holes come exactly under corre sponding little cavities in the ease, in each of which is placed au upright wooden pin with a knob, which prevents its falling. too low: these little pins consequently fall into the holes in the bolt when it is pushed far enough, and the door is locked. In order to unlock it, a bar of wood is passed into the groove in the bolt, and on the bar there are the same number of pins of wood placed upright as there are holes in the bolt and loose pins in the chainbers of the case; and these upright pins are placed so as to corre spond exactly in size and position to the holes; therefore, when theyins reach the holes, they slip into them and push up the loose pins into their respective cavities, and the bolt is then easily pulled back by means of the bar or key. This is simple and ingeni ous, but it is very clumsy, and, as usually made in Turkey, is not secure. Nevertheless, it has been in use longer than any other form of lock in existence.
During the middle ages, very complicated and ingenious locks of various kinds were made, and as much artistic taste was expended upon the ornamentation of their exter nal metal work as there was skill in the interior mechanism. Such locks, however, -were not adapted to general use, and they were only found on the caskets of the wealthy. The ordinary ward mad spring locks were the only ones commonly employed up to the beginning of the present century-, even for important purposes, and this kind of lock is still in very common use. It consists of a bolt of metal, to which a spring is attached, and it is moved backward or forward by means of a key, which by raising the bolt com presses the sprino. in the slot, through which it works, and so lets it pass on until out of the range of the tey's action, which turning on a pivot is regulated by the length of its wards and the depth of a curve cut in the under side of the bolt. In order to prevent any key of the same size opening all such locks, little ridges of iron are placed iu circles or parts of circles, and wards are cut in the keys so as to correspond with them; hence, only the key which has openings or wards which will allow the ridges to pass through them can be used. The bolt has at the end opposite to that which enters the staple a small piece slit, bent outwards, and tempered hard; this forms the spring; below are two notches, divided by a curved piece of the bolt; there is another notch, which if the key enters and is turned round it draws the bolt forward or backward in lockino. or unlocking, and the spring makes the end of the bolt either drop into one of the no12.hes or rise up the curve, according to the distance to which it is pulled. The ridges are so placed as to allow the wards of the key to move freely, and to prevent the entrance of another key of different arrangement.
The tumbler-lock is the type of another class, and is an advance upon the last; the two principles are, however, in most cases combined. The principle of the tumbler lock will be readily understood by a lock nearly like the former, to which a description of the simplest form of tumbler has been added. The bolt has neither the string
piece nor the notches and curves on the under side, but it has two notches on the upper side, which are exactly as far apart as the distance moved by the bolt in locking or unlocking. Behind the bolt is the tumbler, a small plate moving on a pivot, and having projecting from its face a small square pin, which when the bolt is locked or unlocked falls exactly, into one or the other of the small notches. There is in the key a notch -which corresponds to the outline of the tumbler. This acts upon the tumbler when the key is turned, and raises it so as to lift the pin out of the notch in the bolt, and allow the latter to be moved freely forward until the other notch comes under the pin, when the latter falls into and imrnediatly stops its further progress, and the action of the key must be reversed in order to relieve it again. This very simple applicatios. of the tumbler is sufficient to explain the principle which may be and is varied to an almost endless extent. Chubb's justly celebrated lock carries it out most fully, the bolt itself being only a series of tumblers, with a notch on the key for each. Braman's lock, patented in 1788, has enjoyed immense reputation, chiefly for cabinets, desks, and other similar applications; it is very different in principle from those before-mentioned, con sisting of a number of movable slides or interior bolts working in an internal cylinder of the lock, and regulated by the pressure upward or downward of the key acting on a spiral spring. For ordinary purposes it is very secure; but when the most perfect security is required, the beautiful lock invented by Mr. Cotterill of Birmingham, and the still more ingenious one of 3Ir. Hobbs of America, must be preferred. These beau tiful and cotnplicated pieces of mechanism cannot be described within the limits of this article; but ample information upon them and others can be found in Mr. Denison's Treatise on Locks, and in The Rudimentary Treatise on the Construction of Loeb, by Charles Tomlinson.
LOCK (ante). An important class of locks are what are called permutation and dial locks, and are used upon burglar-proof safes. One of the principal devices in them is the etnployment of a number of wheels. placed near together, on an axis on which they move independently. These wheels do not interfere with the motion of each other except when certain pins are brou,ght in Contact, the pins being movable at the will of the person adjusting the lock. In this way one having knowledge of the combination may arrange the wheels so that certain slots in their peripheries will not coincide, and can not be made to coincide, by any one not in possession of the arrangement. The person. having such knowledge may, however, readily place the slots imo liue and pass a key through them, by which means alone the bolt of the lock is moved. An ingeniously arranged dial is placed on the ,outside of the safe door, through which a bolt passes attached in the lock to a wheel. This fixed wheel can be turned one way or another, and, being provided with a pin, the first of the movable wheels may be 'turned so that its slot will correspond to any number on the dial. This first movable wheel, being also pro vided with a pin upon its disk, is made to turn the second wheel to a certain position, and so on to the last wheel, when, the slots being all brought iuto line, the key is intro duced. There are a great many varieties of these locks, each possessing various advan tages. As buiglars often compel the person having the knowledge of the combination of a lock to reveal the secret, it is often the practice to employ for bank-vaults locks with a clock-work attachment by means of which the bolt is liberated at a certain hour, until which time, nobody, not even the person possessing a knowledge of the combina ation, can open the lock.