chubb’s lock.

383

of its own key. The detector is the great andpeculiar feature by which Chubb’s lock is so wellknown.

“ In fig. 173, “ a is the bolt, b the square studrivetted into and forming part of the bolt; c arethe levers, six in number, moving on the centrepin d , placed one over the other, but perfectlyseparate and distinct, so as to allow all of themto be elevated to different heights, e is a dividingspring, forming six separate springs, pressing uponthe ends of the six levers, f is the detector-spring.It will be observed that the bottom lever has atooth near the detector-spring, g is a stud or pin,fixed into and forming part of the bottom lever,and h is the key. Now it will be obvious that thewhole of the levers must be lifted precisely to thedifferent heights required, to allow the square studb to pass through the longitudinal slots of thelevers, so that the bolt may be withdrawn. Thereis no means of telling when any one lever is liftedtoo high, or not high enough, much less can thecombination of the six be ascertained; and if a falsekey should be inserted, and any one of the leversshould be raised beyond its proper position, thedetector-spring/will catch the bottom lever c, andretain it, so as to prevent the bolt from passing;and thus, upon the next application of the truekey, immediate notice will be given of an attempthaving been made to pick the lock, as the true keywill not then at once unlock it. By turning the