THE STEAM-ENGINE. 



459 



the steam ; and they are kept shut by the working-gear. We have erected an 

 engine at Messrs. Goodwyne and Cp.'s brewery, East Smithfield, London." 



By the contrivance which has been explained above, the force of the piston 

 in ascending and descending would be conveyed to the working end of the 

 beam ; and the next problem which Watt had to solve was, to produce by the 

 force exerted by the working end of the beam in ascending and descending a 

 continuous motion of rotation. In the first instance he proposed to accomplish 

 this by a crank placed upon the axle to which rotation was to be imparted, and 

 driven by a rod connecting it with the working end of the beam. Let K, fig. 19, 



Fig. 19. 



be the centre, to which motion is to be imparted by the working end H of 

 the beam. On the axle K suppose a short lever K I to be fixed, so that when 

 K I is turned round the centre K, the axle must turn with it. Let an iron rod, 

 the weight of which shall balance the piston and piston-rod at the other end 

 of the beam, be connected by joints with the working end H of the beam, and 

 the extremity I of the lever K I. As the end H of the beam is moved upward 

 and downward, the lever K I will be turned round the centre K, taking suc- 

 cessively the positions represented by faint lines in the figure ; and thus a mo- jl 

 tion of continued rotation will be imparted to the axle K. 



