436

ON LOCKS AND KEYS.

Fig. 216 represents the next improvement bywhich the previous faults were corrected, inasmuchas the levers are vertical and slide up by the actionof the key, and are forced downwards by thesprings acting on their tops.

It must be particularly noticed that Mr. Parsonsintroduced an improvement into the two-sided lockswhich has never been improved upon or followedby other makers. It consisted in putting into suchlocks two drill-pins—one on each side of the lock—and consequently each set of levers were differentlygated, and the keyhole on each side of the lockbeing in a different position, prevented a directaperture through the lock.

By this method the same amount of security isobtained in a two-sided lock as in a single-sidedone. In all other two-sided locks the security isin the proportion of one to ten between them andone-sided, or the regular locks.

This plan effectually prevents the key-pin frombeing seen on either side of the door, and conse-quently is a certain guard against the lock beingopened by means of nippers being applied to theend of the key-pin, as was the case in Liverpooland other places a short time ago, by a gang ofAmerican thieves, who succeeded in unlocking thedoors of the chambers of commercial men, androbbing their pockets or portmanteaus of the con-vertible contents. We understand that the lockson the chamber doors in France are constructed