444 



THE STEAM-ENGINE. 



kinds of mills from the reciprocating motion of a steam-engine. He proposed 

 to accomplish this by means of two endless chains passing over pulleys, which 

 should be moved upward and downward by the motion of the engine, in the 

 manner of a window-sash. The joint pins of the links of the two chains 

 worked in teeth at the opposite sides of a cog-wheel, to which they imparted 

 a circular motion, first by one chain, and then by the other, acting alternately 

 on opposite sides of the wheel. One chain impelled it during the descent of 

 the piston, and the other during the ascent ; but one of these chains always 

 passed over its pulleys so as to produce no effect on one side of the cog-wheel, 

 while the other chain worked on the opposite side to turn it round. For 

 this purpose each chain was provided with a catch, to prevent its circulating 

 over its pulleys in one direction, but to allow it free motion in the other. The 

 cog-wheel thus kept in revolution might be applied to the axis of any mill 

 which the engine was required to work. Thus, if it were applied to a flour- 

 mill, the millstone itself would perform the office of a fly-wheel to regulate the 

 intermission of the power, and in other mills a fly-wheel might be added for 

 this purpose. 



The hints obtained by Mr. Stewart from Papin's contrivance, before men- 

 tioned, will not fail to be perceived. In Mr. Stewart's paper he notices indi- 

 rectly the method of obtaining a continued circular motion from a reciprocating 

 motion by means of a crank or winch, which, he says, occurs naturally in 

 theory, but in practice would be impossible, from the nature of the motion of 

 the engine, which depends on the force of the steam, and cannot be ascertained 

 in its length. Therefore, on the first variation, the machine would be either 

 broken in pieces or turned back. Such an opinion, pronounced by a man of 

 considerable mechanical knowledge and ingenuity, against a contrivance which, 

 as will presently appear, proved in practice, not less than in theory, to be the 

 most effectual means of accomplishing the end here pronounced to be impossi- 

 ble, is sufficiently remarkable. It might cast some doubt on the extent of Mr. 

 Stewart's practical knowledge, if it did not happen to be in accordance with a 

 judgment so generally unimpeachable as that of Mr. Smeaton. This paper of 

 Mr. Stewart's was referred by the council of the royal society to Mr. Smeaton, 

 who remarked upon the difficulty arising from the absolute stopping of the 

 whole mass of moving power, whenever the direction of the motion is changed ; 

 and observed, that although a fly-wheel might be applied to regulate the motion, 

 it must be such a large one as would not be readily controlled by the engine 

 itself ; and he considered that the use of such a fly-wheel would be a greater 

 incumbrance to a mill than a water-wheel to be supplied by water pumped up 

 by the engine. This engineer, illustrious as he was, not only fell into the 

 error of Mr. Stewart in respect of the crank, but committed the further blunder 

 of condemning the very expedient which has since rendered the crank effectual. 

 It will presently appear that the combination of the crank and fly-wheel have 

 been the chief means of establishing the dominion of the steam-engine over 

 manufactures. 



In 1779, Mr. Matthew Wasbrough, an engineer at Bristol, took out a patent 

 for the application of a steam-engine to produce a continuous circular motion 

 by means of ratchet-wheels, similar to those previously used by Mr. Oxley, 

 at Hartley colliery ; to which, however, Mr. Wasbrough added a fly-wheel to 

 maintain and regulate the motion. Several machines were constructed under 

 this patent ; and among others, one was erected at Mr. Taylor's saw-mills and 

 block manufactory at Southampton. In 1780, one was erected at Birmingham, 

 where the ratchet-work was found to be subject to such objections, that one 

 of the persons about the works substituted for it the simple crank, which has 

 since been invariably used. A patent was taken out for this application of the 



