■'2^4 IMPROVEMENT IN THE CONSTRUCTION 



tlon of whicli, the following extrad is made, which will be 

 fufficiently inlUuftive to thofe who are acquainted with thie 

 ful)jea. 

 Extrafl; from " l^ 'he engine be conflrii61ed originally with the inten- 



Mr Woolf's (Ion of adopting my faid improvement, it ought to have two 

 * *' fleam veflels of different dimenfions, according to the tem- 



perature or the expanfive force determined to be communi- 

 cated to the fieam made ufe of in working the engine; for the 

 fmaller fleam vefTel or cylinder mud be a meafiire for the 

 larger. For example, if fleam of forty pc^unds t))e Iquare 

 inch is fixed on, then the fmaller fleam veflel ihould beat leaft 

 one fortieth part the contents of the larger one; each fleam 

 vcfTel fliotild be furnitlied with a piflon, and the Imaller cylin- 

 der Qiould have a communication both at its top and bottom 

 (top and bottom being here employed merely as relative terms, 

 for the cylinders may be worked m a horizontal or any other 

 required pofition, as well as vertical) : the fmall cylinder, I 

 fay, tlioiild have a communication both at its top and bottom 

 with the boiler which fupplies the fleam, which communica- 

 llons, by means of cocks or valves of any conftruction adapted 

 to the ufe, are to be alternately opened and fliut during the 

 working of the engine. The top of the fmall cylinder (bould 

 have a communication with the bottom of the larger cylinder, 

 and the bottom of the fmaller one with the top of the larger, 

 with proper means to open and fliut thefe alternately by corks, 

 valves, or any other well-known contrivance. And both the 

 top and bottom of the larger cylinder or fleam veflel, fliould, 

 while the engine is at work, communicate alternately with a 

 condenfing velTel, into which a jet of water is admitted to 

 liaflen the condenfation, or the condenfing veffel may be cooled 

 by any other means calculated to produce that effedt. Things 

 being thus arranged, when the engine is at work, fleam of high 

 temperature is admitted frorn the boiler to a6l by its elaftic 

 force on one fide of the fmaller. piflon, while the fl'cam which 

 bad laft moved it has a communication with the larger fleam 

 veifel or cylinder, where it follows the larger piflon now moving 

 towards that end of its cylinder which is open to the condenf- 

 ing velfel. Let both piftonsend their flroke at one time, and 

 Jet us now fuppofe them both at the top of their refpedtive cy- 

 linders, ready todefcend; then the fleam of forty pounds the 

 ffjuare inch entering above the fmaller piflon will carry it down- 

 wards. 



