dr. Andrews’ (a.merica) lock.

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withdrawing of the bolt. The owner can, however,before the fixing of the bolt, adopt any arrangementof tumblers and hits which he may choose. Butthough the tumblers cannot be actually re-arrangedin any new order within the lock while the latteris fixed, yet by an ingenious contrivance the tum-blers can be so acted upon as to render the lockpractically different from its former self. The pur-chaser receives with his lock a series of small steelrings, each ring corresponds in thickness with thethickness of some one of the bits of the key; sothat, by suitable adjustment, any one of the hitsmay be removed from the key, and a ring be sub-stituted in its place. The effect of this substitutionis, that the particular tumbler which correspondswith the ring is not raised by it; it is drawn outwith the bolt, as if it were part of the bolt itself.Supposing the lock to he locked by this means, theoriginal key would not now unlock it; for one ofthe tumblers has now been displaced, and can onlybe re-adjusted by the same ring which displaced it.If an attempt he made to open the lock by theoriginal key, or by the key in its original adjust-ment, a detector is set in action, which indicatesthat a false key or other instrument has been putinto the lock. One, or more than one, of the bitsmay be removed from the key, and rings be sub-stituted, and consequently one or more of thetumblers may be disturbed in this peculiar way;so that the lock may change its character in all