^P STEAM-ENGINES. ;265 



wards, while the fleam below it, inftead of bein^ aHo'.ved to Extrafi frrm 

 efcape into the atmofphere or applied to any other purpofe, ^i"' Woolf \ 

 will pafs into the larger cylinder above its pifton, which will 

 take its downvvard flroke at the faiTie time that the pifion of 

 the fmaller cylinder is doing the fame thing; and while this 

 goes on, the fteam which lad filled the larger cylinder, in the 

 upward (hoke of the engine, will be paffing into the conden- 

 (er to be condenfed during the downward ftroke. When the 

 piftonsin the fmaller and larger cylinder have thus been made 

 to defcend to the bottom of their refpedlive cylinders, then 

 the fleam from this boiler is to be fliut off from the lop and 

 admitted to the bottom of the fmaller cylinder, and the com- 

 munication between the bottom of the fmaller and the top of 

 the larger cylinder is alfo to be cut off, and the communication 

 to be opened between the top of the fmaller and the bottom 

 of the larger cylinder; the rteam, which in the downward 

 (Irokeof the engine filled the larger cylinder, being now open 

 to the condenfer, an.i the communication between the bottom 

 of the larger cylinder and the condenfer fliut off; and fo on 

 alternately, admitting the fieam to the different (ides of the 

 fmaller piflon, while the fteam lafi admitted into the fmaller 

 cylinder palfes alternately to the different fides of the larger 

 pifton in the larger cylinder, the top and bottom of which are 

 made to communicate alternately with the condenfer. 



^* In an engine working with the improvements which have 

 been juft defcribed, while the fteam is admitted to one (jde of 

 the pifton in the fmaller cylinder, itie fteam on the other fide 

 has room made for its admithon into the larger cylinder, on one 

 fide of its pifton, by the condenfaiion going on on the other 

 fide of the large pilton which is open to the condenfer ; and 

 that wafte of fteam which lakes place in engines worked only 

 by the expanfive force of fteam, from fteam pafting the pifton, 

 is prevented ; tor all fteam thai palles tlie pifton in the fmaller 

 cylinder is received into the larger. 



" In fuch an enjjine, where it may be more convenient for 

 any particular puipofe, the arrangement may be altered, and 

 the top of the fmaller made to commmiicaie with the top 

 of the larger, and the bottom of the hiialler with the bottom 

 of the larger cylinder; in which cafe the only difference will 

 i)e, that when the pifton in the fmaller cylinder defcenUs, that 



