LOCK

(Saxon, loc.) An instrument composed of springs and bolts, used to fasten doors, drawers, chests, . A good lock is the masterpiece in smithery, and requires much art and delicacy in contriving and varying the wards, springs, bolts, and other parts whereof it is composed, so as to adjust them to the places where they are serviceable, nnd to the various occasions of their use. The structure of locks is so varied, and the number of inventions of different sorts so extended,that we cannot attempt to enumerate them. Those placed on outer doors are called stock locks, those on chamber doors spring locks, and such as are hidden in the thickne of the doors to which they are applied are called mortise locks. The padlock is too well known to need description. We here add the conditions which, to Mr. Nicholson, appear nece ary in a lock of the most perfect kind: 1. That certain parts of the lock should be variable in position through a great number of combinations, one only of which shall allow the lock to be opened or shut. 2. That this last mentioned combination should be variable at the pleasure of the po e or. 3. That it should not be po ible, after the lock is closed and the combination disturbed, for any one, not even the maker of the lock, to discover, by any examination, what may be the proper situations of the parts required to open the lock. 4. That trials of this kind shall not be capable of injuring the works. 5. That it shall require no key; 6. And be as easily opened in the dark as in tlie light 7. That the opening nnd shutting should be done by a proce as simple as that of a common lock. 8. That it should open without a key, or with one, at pleasure. 9. That the keyhole be concealed, defended, or inacce ible. 10. That the key may be used by a stranger, without his knowing oi [s. 690]