1858.] on some Improvements in fjocks. 477 



equal to the best locks of 1851, are now sold by him at 27*. a 

 dozen, and by Mr. Tucker, and perhaps other makers, at about the 

 same price. It may be as well to mention that the piece called the 

 " detector," by which the Chubb lock gained so much of its cele- 

 brity, is of no use whatever towards the prevention of picking by 

 the method which is now generally connected with Mr. Hobbs's 

 name ; though it is in reality much older, and been actually pub- 

 lished in a former edition of the Encyclopcudia Britannica, 30 

 years ago, as applicable to the Bramah lock as first made, without 

 false notches ; only no one had ever thought of applying it to 

 tumbler locks, which were invariably made without false notches 

 before 1851, with the single exception of Strutt's lock, which was 

 invented in 1819, but never came into general use. 



It should be observed that the mere variety of locks of different 

 constructions, and the same outward aspect, is to a certain extent 

 a source of security. Formerly, a thief knew almost by looking at 

 the key-hole, of whose make and of what construction a lock was ; 

 but there are now so many locks and keys, all of the same general 

 appearance, that you can no longer tell by the mere look of the 

 outside what kind of machinery you have to deal with inside ; any 

 more than Mr. Hobbs knew, when he accepted a challenge to 

 pick one of Mr. Cotterill's locks, that it contained an additional 

 contrivance not to be found in those locks as generally made and 

 sold, and therefore of course he failed, though the Cotterill locks 

 commonly sold are quite as easy to pick as Bramah's, and in just 

 the same way. 



The principle of all locks above the rank of the common 

 warded locks, whatever may be the details of their arrangement, is 

 this : — There are a number of similar pieces (which may have the 

 name of tumblers, levers, sliders, discs, rings, or pins, according to 

 circumstances), each with a notch in it at a different place ; and 

 until all these notches are brought together into one given position, 

 the pieces in question, or some of them, prevent the passage of 

 another piece in the lock, on which its opening depends. Mr. 

 Denison exhibited a model, made not to resemble any particular 

 lock, but to illustrate this general principle of them all ; and he 

 showed on it the application of the "tentative" mode of picking 

 by applying pressure to the bolt, and then gently moving each of 

 the tumblers or sliders, &c., in succession, on which any pressure is 

 felt, until all their notches come under the piece which has to enter 

 them, and then the bolt yields to the pressure, and goes back 



As soon as the vincibility of all the best English locks by this 

 method had been demonstrated in 1851, the makers of tumbler 

 locks began re-inventing several old contrivances, and especially 

 the false notches of Strutt's lock of 1819, or it may be said, of 

 Bramah's lock of 1817 ; for all the good Bramah locks (includ- 

 ing the very one on which Mr. Hobbs won the 200 guineas) 

 had been made with false notches since that time ; and tumbler 



