Page:A Dissertation on the Construction of Locks (1785).pdf/42

 whether lifted by the elaſtic power of the ſprings, on which they reſt; or ſunk by the preſſure of a ſuperior weight from above. The part, which projects from the oppoſite ſide of the joint, or carriage, A, and inſerts its extreme point in the bolt, at C, is a lever of a different form, which acts in ſubordination to thoſe above deſcribed; to this lever, two offices are aſſigned, the one to keep the bolt in a fixed, and immoveable poſition, in the abſence of the key;—the other to give it its proper motion, when the key is applied. The joint, or carriage of the levers, and the ſprings on which the levers bear, are fixed on a circular platform, D, which turns on a center; and in its motion impels the bolt, in either direction, by means of the lever, which is projected from the joint A.—To give this machine the property of inviolable ſecurity, it was neceſſary to ſubject its motion to ſome reſtraint, which the key only could remove. This power is lodged in the part