(105.) Papin, to whom the credit of discovering the method of producing a vacuum by the condensation of steam is due, was the earliest and most remarkable of those projectors. With very limited powers of practical application, he was, nevertheless, peculiarly happy in his mechanical conceptions; and had his experience and opportunities been proportionate to the clearsighted character of his mind, he would doubtless have anticipated some of the most memorable of his successors in the progressive improvement of the steam engine. In his work already cited, after describing his method of imparting an alternate motion to a piston by the atmospheric [Pg179] pressure acting against a vacuum produced by the condensation of steam, he stated that his invention, besides being applicable to pumping water, could be available for rowing vessels against wind and tide, which he proposed to accomplish in the following manner. Paddle-wheels, such as have since been brought into general use, were to be placed at the sides, and attached to a shaft extending across the vessel. Within the vessel, and under this shaft, he proposed to place several cylinders supplied with pistons, to be worked by the atmospheric pressure. On the piston-rods were to be constructed racks furnished with teeth: these teeth were to work in the teeth of wheels or pinions, placed on the shaft of the paddle-wheels. These pinions were not to be fixed on the shaft, but to be connected with it by a ratchet; so that when they turned in one direction, they would revolve without causing the shaft to revolve; but when driven in the other direction, the catch of the ratchet-wheel would act upon the shaft so as to compel the shaft and paddle-wheels to revolve with the motion of the pinion or wheel upon it. By this arrangement, whenever the piston of any cylinder was forced down by the atmospheric pressure, the rack descending would cause the corresponding pinion of the paddle-shaft to revolve; and the catch of the ratchet wheel, being thus in operation, would cause the paddle-shaft and paddle-wheels also to revolve; but whenever the piston would rise, the rack driving the pinion in the opposite direction, the catch of the ratchet wheel would merely fall from tooth to tooth, without driving the paddle-shaft.