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one, without falling into the other. And a very little thought on the ſubject, convinced me, that my ſucceſs would depend on the application of a principle, as diſſimilar as poſſible, to that, by which other projectors had in vain ſought to attain perfection, in the art of Lock-making. And as nothing can be more oppoſite in principle to fixed Wards, than a Lock which derives its properties, from the motion of all its parts, I determined, that the conſtruction of ſuch a Lock, ſhould be the ſubject of my experiment.—In the proſecution of my purpoſe, various models were conſtructed; and I had the ſatisfaction to receive from the leaſt perfect of them, the cleareſt demonſtration of the truth, and certainty of my principle. The excluſion of wards, made it neceſſary to cut off all communication between the key and the bolt; as, the ſame paſſage, which (in a Lock ſimply conſtructed,) would admit the key, might give admiſſion likewiſe to other
