Permstatioa Leda Of these, the simplest is a kind of padlock termed a puede lock, which opens without a key, but Is regarded rather as an ingenious toy than as an available substitute for locks. In the commonest form a bar, with square or other projections, is slipped through a series of circular discs, each of which is capable of being turned round upon it as an axis. The apertures through the centre of, these discs are so formed that unless the whole of them are turned round to the exact position they occupied when the bar was slipped in, it cannot be withdrawn. To provide for bringing the rings to this position the periphery of each is marked with a series of letters or numbers, a certain predetermined combination of which must be brought into a straight line by turning the several rings round with the thumb and finger. As the number of combinations which may be effected, like the number of changes in the relative positions of the sliders of a Bramah's lock, is almost infinite, while only one combine thin will amble a person to open the lock, a high degree of security may thus be attained. Many varieties of this lock have been invented. One, by Mr. Mackinnon. is a tumbler lock, in which each tumbler is numbered, and a corresponding number is stamped upon each of a series of small plates, which, when put together upon an axis at the end of the shank of the key, as represented in 11** 17, constitute a bit resembling that of the key of an ordinary tumbler lock. Each bit is pierced with two holes, one of such a form as to fit upon the pear shaped end of the shank, while the other is round, to receive a pin which is attached to the uppermost or end member of the bit, and which passes through all the others, as indicated by the dotted lines in a. A small bole in the end of the shank serves to receive a screw by which all the parts of the bit are kept firmly in their place. The end division of the bit, at bleb is not numbered, in that intended to shoot the bolt; others, marked 1, 2, 3, 4, and 5, may be varied in position at pleasure, ao as to correspond with similar changes in the positions of the tumblers, or so as to unfit the key for opening the lock. In some locks increased complexity is obtained by the use of two distinct sots of tumblers, capable of impediog each other's motion except when rightly acted upon.
Some locks have been made in which the action depends on the key being a powerful magnet. In others the difficulty of opening is in ert-steed by requiring a peculiar method or applying the key. In 'swoon'. lock there is a sliding curtain, by which, it is stated, " the key hole is so perfectly closed during the act of unlocking, that it would be Impossible to move the bolt while a pick retnaina in the aperture." In Gottlieb'. lock, • piece of paper is so placed that no key can be put In wifhout perforating it, and that it cannot be removed excepting by an application of the proper key. In Itutherford's lock, tb"re is a seep-plate to the bolt. rendering it Impossible to open the lock with its own key until, by the action of clockwork within or con nected with the lock, the stop-plate should be brought into a certain position. Many contrivances have been effected for attaching an alarum to locks by which the Introduction of a false key should rings bell or ire a pistol. The compound locks generally used fur the doers of iron sofas, and for ssimiLar purposes, though ponderous and compll. attest In spimanutee, are, In reality, of simple constniction. Although they often throw out bolts on each side, and towards the t .p and bottom of the door, these are usually but so many branches of four massless pieces of Imo, capable of being simultaneously projected or retracted by a handle in the centre of the door ; the actual lock being but small, and merely intended to move an apparatus by which the great bolts are themselves locked; so that the key may be small in proportion to the bolts by which the door is secured. Among the
useful inventions relating to street-door locks is Chubb's combination latch, which combines the simple lifting action of the ordinary French latch, or that which opens with a handle inside the door, and with a key from without, with much of the security of a tumbler-lock.
In the above description of the three principal classes into which locks may be grouped, wo have only noticed a few examples in each class to illustrate the general principle. Our limits will not permit more detailed treatment. The number of patents relating to locks is immense, and every year is adding to it. In mentioning such cele brated makers as Chubb and Bramah, we hare adverted chiefly to the original patents on which their locks were constructed ; but numerous patents have subsequently been obtained by the same makers, which, though adhering pretty nearly to the some principle, exhibit wide diversities in detail. The earlier patents, too, have long since run out; and many other makers now construct locks involving the essential principles of the earlier Chubb and Brsmeh locks, though known by other names.
A very remarkable stimulus was given both to the invention and the manufacture of locks by occurrences which arose out of the Great Exhibition of 1851. Until that year, American locks were little known in England ; but it then became known that great ingenuity had been displayed in this art beyond the Atlantic; and also, that the factory system. aided by machinery, was adopted to an extent far a-head of that followed by the lock.makera of En ,land. Stausbury's lock, one of the American inventions, is a modification of the Egyptian lock. Yale's lock bears some resemblance to the Brantah ; but it has two concentric cylinders working ono within another. Andrcws'a bank lock is constructed on the principle of changing the interior mechanism at pleasure, and adapting the moveable bits of the key to suit it, so as to produce a comparatively new lock by every change. Andrews's snail. wheel lock has a series of revolving discs to take the place of tumblers. Newell's lock, like Andrew's bank-lock, has a provision for altering the tumblers and key at pleasure without removing the lock from the door, or essentially altering its mechanism ; but this is brought about by the use of two sets of tumblers, the one to receive motion from the other, and having different offices to fill ; namely, the key to act upon the first series, and the second series to act upon the bolt. The American parautoptie (secret) bank-lock, invented by Mr. Newell when he found that his former lock was not proof against picking, coutaius a very elaborate series of primary and secondary tumblers, the positions of which aro subject to curious changes by tho action of the key itself ; the owner can change the arrangement of the bits of the key at pleasure ; these bits re-arrange the tumblers in the act of lock ing; and then the lock cannot be opened with the former arrangement of bits in tho key. This lock obtained a high reputation in America and on the continent ; and in 1851 Messrs. Day and Newell took out an English patent for it. Mr. Hobbs afterwards produced his pro tector-lock, a cheaper and more generally useful variety ; it is a modification of the six-tumbler lock, and contains a small piece called a moveable stump, which resists the withdrawal of the bolt until acted upon by the proper key. Another lock by Hobbs has for its the absolute closing of the key-hole during the process of locking, which is effected in a most curious but complicated manner.