Page:A Dissertation on the Construction of Locks (1785).pdf/19

 their labours. Locks have been conſtructed, and are at preſent much uſed, and held in great eſteem; from which the picklock is effectually excluded; but the admiſſion of falſe keys is an imperfection for which no lockſmith has ever found a corrective; nor can this imperfection be remedied whilſt the protection of the bolt is wholly confided to. For, if a Lock of any given ſize be furniſhed with wards in as curious and complete a manner as it can be; thoſe wards being neceſſarily expreſſed on what is termed by lockſmiths the bit or web of the key, do not admit of a greater number of variations than can be expreſſed on that bit or web; when therefore as many Locks have been completed of the given ſize as will include all the variations which the ſurface of the bit will contain, every future Lock muſt be the counterpart of ſome former one, and the ſame key which opens the one will of courſe unlock the other. It hence follows, that