296 Further Particulars respecting Woolf's Sleam-Engine. 



A, the large cylinder, B the little cylinder, each in its steam' 

 case. The steam is admitted from the hoiler into the steam- 

 case of the large cylinder by a communication at C, and there 

 is a communication between this steam-case and that of the 

 small cylinder, so that both of the steam -cases become part of 

 the communication between the boiler and the little cylinder. 

 D furnishes a communication for carrying back to the boiler any 

 water that may be produced by condensation in the steam-case, 

 before the engine is got up to her proper temperature. 



E is the pipe from the steam-case to the esigine, with its 

 regulating valve. F the valve-box; the spindle of the one valve 

 working through that of the other. The passage for the steam 

 from the case into the small cylinder is between the two valves, 

 G is the valve that opens the communication !)etvveen tl\e bottom 

 of the small cylinder B and the toj) of the large cylinder A. 



H is the valve that returns the steam from above to below 

 the large piston; and I is the exhaustion valve. 



When the engine makes its stroke, the upper valve at F suf- 

 fers the steam to pass from the boiler (through the steans case) 

 upon the small piston; the valve G at the same time allows the 

 steam to pass from the underside of the small to the upper side 

 of the large piston, and the valve I opens to the condenser. 

 These three valves open at the same instant of time. 



When both pistons arrive at the bottom these valves shut, and 

 the lower valve at F opens to return the steam from above to, 

 below the small piston ; the valve H doing the same to the large 

 one, and the engine returns in equilibrium : but the upper 

 valve at F can be shut off at any part of the stroke, according 

 to the load of the engine. 



Those who are conversant with steam-engines will perceive, 

 from the passing of the steam as above described from the upper- 

 to the lower side of each of the pistons respectively, that the 

 engines at Wheal Var and Wheal Abraham are at present work- 

 ing single. Were these engines working double, the steam 

 would on the down stroke be made to pass from the under side 

 of the small to the upper side of the large piston, steam in the 

 mean time coming in upon the small piston and the under side 

 cf the laige being open to the condenser ; and on the up -stroke 

 steam would pass from the top of the small under the large pis- 

 ton, while steam was received from the boiler under the small 

 piston, and the top of the large cylinder open to the condenser. 



Fig. 2 represents another method of arranging and ajjplying 

 the power of WooF's engine ; for the arrangement admits of 

 great variety of modification. The valves will be understood 

 from the foregoing description of those of fig. 1 ; but the mode 

 of working the engine fig, 2 is different. In this the steam is 



made 



