442 



THE STEAM-ENGINE. 



In his work, after describing bis method of imparting an alternate motion to 

 a piston by the atmospheric 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 pis- 

 ton-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 com- 

 pel 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 pad- 

 dle-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. 



It is evident that by such an arrangement a single cylinder and piston would 

 give an intermitting motion to the paddle-shaft, the motion of the wheel being 

 continued only during the descent of the piston ; but if several cylinders were 

 provided, then their motion might be so managed, that when one would be per- 

 forming its ascending stroke, and therefore giving no motion to the paddle-shaft, 

 another should be performing its descending stroke, and therefore driving the 

 paddle-shaft. As the interval between the arrival of the piston at the bottom 

 of the cylinder and the commencement of its next descent would have been, 

 in the imperfect machine conceived by Papin, much longer than the time of 

 the descent, it was evident that more than two cylinders would be necessary to 

 insure a constantly-acting force on the paddle-shaft, and, accordingly, Papin 

 proposed to use several cylinders. 



. In addition to this, Papin proposed to construct a boiler having a fireplace 

 surrounded on every side by water, so that the heat might be imparted to the 

 water with such increased rapidity as to enable the piston to make four strokes 

 per minute. These projects were promulged in 1690, but it does not appear 

 that they were ever reduced to experiment. 



Savery proposed, in his original patent, in 1698, to apply his steam-engine 

 as a general prime mover for all sorts of machinery, by causing it to raise water 

 to make an artificial fall, by which overshot water-wheels might be driven. 

 This proposal was not acted on during the lifetime of Savery, but it was at a 

 subsequent period partially carried into eftbct. Mr. Joshua Rigley erected 

 several steam-engines on this principle at Manchester, and other parts of Lan- 

 cashire, to impel the machinery of some of the earliest manufactories and 

 cotton mills in that district. The engines usually raised the water from sixteen 

 to twenty feet high, whence it was conveyed to an overshot wheel, to which 

 it gave motion. The same water was repeatedly elevated by the engine, so 

 that, no other supply was necessary, save what was sufficient to make good the 

 waste. These engines continued in use for some years, until superseded by 

 improved machines.* 



* Farey, Treatise on the Steam-Engine, p. 122. 



