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of the principle; but, to my great admiration, it turned out a complete inſtrument of ſecurity; and gave the cleareſt demonſtration, that the principle was certain and infallible.
SPECIFICATION.
Plate the firſt.—The lines, which croſs the face of the Lock, repreſent ſix levers, which are united in a joint, and turn on a common axis, at the point A. Each lever reſts on a ſeparate ſpring, of ſufficient ſtrength to ſuſtain its weight, or, if depreſſed by a ſuperior force, to reſtore it to its proper poſition, when that force is withdrawn. The curve B repreſents a frame, through which the levers are carried by ſeparate grooves, or paſſages; theſe grooves are exactly fitted in their width, to the thickneſs of the levers, but are of ſufficient length, to allow them a free motion, in a perpendicular direction,
