In many ingenious locks of this character the same object is attained by the use of solid tumblers, carrying studs which pass through open ings in the bolt. In a luck of this description invented by Mr. Sower furl, one of the tumblers is drawn downwards by the key while the others are raised, thus introducing a new complication which greatly increases the difficulty of picking, without adding materially to the cost of the lock.
Chubb's detector lock, the original patent for which was obtained in 1513. is one of the most celebrated locks in fie on the principle above dee-Jibed. Its peculiar merit consists in the addition of a lever, called the dernaor, which is so fixed that, while it does not affect the bolt under ordinary circumstances, it cannot fail to move so as to drop a catch int J the bolt if any one of the tumblers be lifted a little too high, as some of them must inevitably be by any attempt at picking. By thus fixing the bolt immoveably, it not only renders useless any further attempt at picking the lock, but also gives notice of the attempt which has been made, when the proper key is next applied.
In Dramatis lock, which was invented and patented about 17S1, the priliciple of tumblers is applied in a very different manner to that above described, and the use of wards is entirely abandoned. The ordinary mode of shooting the bolt, by the action of the bit of the key, is abandoned ; the oMee of the end of the bit being performed by a stud attached to the end of a cylindrical barrel mounted in the lock, and which contains all its essential plate. fig. 13 represents this barrel, of the actual size, drawn from a street-door latch-lock. In this cut a represents the stud by which, when the barrel is caused to re volve on its axis, the bolt is moved as by the bit of an ordinary key. This revolving motion is imparted to the barrel by the insertion of the 11274 VW 8C1 oar. TOG. T.
end of the key as applied to bring the sliders into the required position for allowing the barrel to turn ; and Fig. 16 represents, at a in pro file, and at 6 in an end view, the key itself separately. The severs. figures, aided by the foregoing description, will show the mode in which' this ingenious lock acts. The whole of the apparatus is securely enclosed in a turned brass box, so that even the ends of the sliders are only visible at the farther extremity of the deep and very small key hole. To prevent the sliders from working too loose, or from dropp ng too far into the barrel, they are made of a thin piece of metal doubled, as shown at c, F g.16; so that their inner ends, having an inclination to spring open, press with sufficient force against the sites of the grooves in which they slide to keep them in position until the pressure of the key is withdrawn. and they are expose I to the counter pressure of the
helical spring. The two additional small notches represented in the tumblers of Fig. 15 and 16, add greatly to the security of this kind of lock.
The variety attainable in the arrangement of locks on this principle forms one of its great recommendations. Our illustrations refer to one of its simplest forms; but even in this form the variety attainable, without any difference in the size of the key. is very great. By the use, however, of more sliders, the number of different locks, each of which may have the same external appearance, but can be opened only by its own proper key, is increased almost to infinity. Bram th showed that if twelve sliders were employed, the number of changes which might be produced by simply varying their relative positions would amount to 479,001,500 ; while by aiding one more slider the number would be increased to 6,227,019,300. In the event of a key being lost, or the owner desiring to have a lock altered, it is possible to change the relative positions of the sliders, so as to render the old key useless. Mager-Ivy, may also be made by constructing a suit of locks alike In everything but the position of their notches, and then applying to each of them in succession the master-key, which mnst have notches differ cut to any c-t the ordinary keys, and cutting additional notch.. in the sliders to suit it.
Owing to the small sire of the protecting apparatus, the liramah lock has been applied to many ingenious purposes for which other kinds of locks are leas suitable, among which we may notice the locking of liqnor-cocks. Mr. Itorelan afterwards Invented what he calls a " lock ," which is, in fact a shield, adapted to cover the key-hole, and sing in its centre a minute lock with seven sliders. By applying this to a key-hole on the outside of a dour, and turning its key a quarter tonne. two lancet-shaped pieces of steel are projected front a little box. in such a manner as to dig into the wood on the opposite sides of the key-bole, and to hold the shield so firmly in its place that nothing abort (.1 the application of violence can remove it, until. by a fresh application of the little key, the blades are withdrawn. A lock was invested by Mr. Kemp, in 1818, in which the peculiarities of both ltarron's and Bratnalie locks are combined in .}.1. a way as to afford, in the inventor's opinion, greater security than can be attained by ' either alone.