168 



THE WATT AND THE TREVITHICK ENGINES. 



TRKVJTHICK'S DOLCOATH 76-iKCH CYLINDER PUMPING ENGINE, ERECTED IN 1816, CEASED 



WORKING 1869. 



o, steam-cylinder, 76 inches in diameter, 9-feet stroke; &, steam-jacket; c, steam expansion-valve, 

 11 inches diameter, double beat; the U)per beat 11 inches diameter, the under beat9| inches, valve 

 8 inches long ; d, expansive cam on plug-rod ; e, plug-rod for moving the gear ; /, expansive horn ; 

 g, equilibrium valve, 13 inches in diameter, single beat moved by a tooth-rack and segment ; h, ex- 

 haust-valve, 141 inches in diameter, single beat moved by a lever and link ; i, equilibrium-valve 

 handle; j, exhaust-valve handle ; k, Y-posts for carrying the gear arbors; I, main beam in two plates 

 of cast iron ; m, parallel motion ; r>, feed pump rod ; o, air-pump bucket-rod, the pump, 2 feet 9 inches 

 diameter ; p, the main pump rods. 



t 



CYLINDER, .MAUN BEAM, AND PUMP-ROD OF DOLCUATH 76-iNCH CYLINDER ENGIMK. 



