MECHANICS AND USEFUL ARTS. 113 



bolt is pushed back, and may be unlocked. If any one turnbler_ is 

 lifted up too far, or not far enough, it will bar the passage of the pin, 

 and the lock cannot be opened. The right key is so shaped that, 

 when turned, its bits perform the duty of lifting these tumblers. 

 When a person skilled in the art, for so it may be termed, attempts to 

 pick such a lock, he first, by some means, (a sharp-pointed, crooked 

 wire, for instance, introduced through the key-hole,) shoves the bolt 

 back until the pin bears forcibly against the faces of the tumblers. 

 By means of another wire, he then shoves up or moves each tumbler 

 separately until the sense of feeling tells him that the notch therein is 

 opposite the pin. An increased facility of motion in the tumbler is 

 one certain guide of this point being reached ; or if the tumblers be 

 weak and the pressure on the bolt strong, a click will be heard, and 

 the tumbler may remain resting precisely at the proper point. As 

 the proper position of each tumbler is ascertained, it is carefully 

 measured and noted down. When all the positions are discovered, 

 each tumbler is lifted and held at the right height, and the bolt is 

 moved, the pin enters the slits and the lock flies open. This opera- 

 tion as described may seem easy, and it is so to those who, to a deli- 

 cate touch and mechanical dexterity, add perfect knowledge not only 

 of the principles of locks, but also of the construction of the precise 

 kind of lock they intend to pick. Those who undertake to pick a 

 lock without these requisites will find their task not only difficult, but 

 absolutely unacconiplishable. 



Another lock patented is powder-proof, and may be loaded through 

 the key hole and fired until the burglar is tired of his fruitless work, 

 or fears that the report of his explosions will bring to view his expe- 

 riments more witnesses than he desires. 



In it the pin on the bolt does not abut against the tumblers, but 

 against other sliding pieces which cannot be reached through the key- 

 hole, having between it and them strong steel partitions. These pieces 

 may be termed secondary tumblers, and are furnished with slits 

 like the tumblers first named in this section. These secondary tum- 

 blers are connected with the true tumblers, through the agency of 

 slender springs, in such manner that the true tumblers will raise the 

 secondary just as they themselves are lifted, when no obstacle ob- 

 structs the movement of the secondary tumblers. Now if the lock 

 be locked, and the proper key applied and turned, it first lifts the true 

 tumblers to the proper height ; these, while being raised, lift the sec- 

 ondaries by the springs until their slits are at the proper height, 

 when the pin enters, and the bolt is retracted by the further turning 

 of the key. If the lock be locked, and an attempt is made to pick it, 

 the bolt is first forcibly shoved back until its pin strikes the edges of 

 the secondary tumblers ; its pressure upon these prevents the light 

 springs from moving them, and the burglar may move the true tum- 

 blers up and down, amusing himself as long as he desires, without 

 altering at all the position of the secondary tumblers, or obtaining any 

 indication as to the locality in which they must be placed before the 

 bolt can be moved. The partitions above named prevent any direct 



