Page:A Dissertation on the Construction of Locks (1815).pdf/40

 The cap or covering plate, m, screws down to the external plate of the Lock, q, limiting the upward pressure of the sliders, and protecting all the operative parts. When the barrel, i, i, is moved round, the bolt, r, is thrown forward by a process which will be hereafter explained.

To give this machine, the property of inviolable curity, it was necessary to subject its motion to some restraint which the key only could remove, a power that is lodged in the thin plate, Fig. 4. This plate, as applied at n, n, Fig. 3, serves either to check or guide the motion of the machine, and these opposite offices the following will explain: on the edge of the plate which grasps the barrel are cut eight notches, into which the sliders, l, l, project; whilst they are thus confined, the motion of the machine is totally suspended, and the bolt so fixed as to defy every effort of art to move it. The sliders are upheld in their respective grooves by the elastic power of the spring on which they rest, till a pressure superior to that power is applied, and are again restored to their station by the re-action of the spring when the weight which depressed it is removed. All these sliders, as before observed, have a notch on the outer edge, disposed as irregularly as possible, and