ike original Invention of the Steum-Engini. 42 1 



allowable for a philofoplier to conclude that the experiments of another are falfe or impoffi- 

 blc, becaufe they do not ngree with his own. I fuppofe Defaguliers made his experiments 

 witli more wine andmore heat than Savery ; and if I were difpofed to reafon againft the 

 relation of a pcfitive faft, I fliould be inclined to doubt the proje£lion of the fia{k againfl: 

 the ceiling by an exertion of atmofpherical prelfure, which mud have been as ftrong on the 

 outer as on the inner furfacc of the veflel. And in this doubt I Ihould be ftill more fettled, 

 from having myfcif very often repeated the experiment without any fuch refult. But the 

 integrity of Dsfa;^uliers forbids any fuch infinuatiou. Under certain circumftances the 

 flaik might have been beaten out of his hand -, but it does not follow that thofe circum- 

 ftances were prefent in Captain Savery 's experiment. 



The Marquis of Worcefter was the firft inventor of the fteam-engine. Savery was either 

 the fecond inventor, or he had the ingenuity to difcern a valuable invention in the midtl of" 

 loofe hints, and to give it-organization and efFedl. 



We do not know how the Marquis of Worcefter condenfed his fteam, or, indeed, whe- 

 ther he condenfed it at all ; for it certainly does not require condenfation unlefs for what is- 

 called fucking. It is faid, that the condenfation in the firft engines was effefted by water on 

 the outfide of the veflt;l ; but in Savery's engines it was performed within the vefltil. Seve- 

 ral of his engines were made with only one fteam-yeflel, and Defaguliers found by experiment, 

 that this kind is confiderably better than fuch as have two ; becaufe the action of the fteara 

 is rendered more ludden, and the chemical condenfation during the procefs of forcing is 

 lefs. This excellent philofopher and pradlical engineer made feveral other improvements 

 in this engine and its parts, which may be feen in his work laft quoted : but the fubfequent 

 invention of the fteam engine with a pifton and lever, and the improvements which have been 

 made therein, feem to have greatly retarded the progrefs of the original fimple machine. 



Dr. Papin, well known for his invention of the digeftor, was bufied in experiments on 

 fteam. Prony, in his ArchiteiSlure HydrauHque, i. 5(16, mentions a work of his, printed at 

 Caflel in 1 707, under the title of Notivetle Maniere d'elever PEau par la Force de Feu, in which 

 a fleam-engine is defcribed which differs from that of Savery, but may equally accord with the 

 defcription of the Marquis of Worcefter. From the engraving, fig. 268, in his fecond vo- 

 lume, it appears to have confifted of a fpheroidal boiler, a cylindrical fteam^vefli;! into which 

 was fitted a float or pifton, and an airveflel which received the water from each ftroke 

 previous to its being forced by re-a£lion to a greater height. The water flowed through a pipe 

 ■with a valve opening downwards, whence it pafled beneath the pifton which floated upon it. 

 The defcent of the pifton was effefted by the fteam, and its afcent byjthe af^ion of the wa- 

 ter from the original ftock ; at which period the fteara was fuftered to efcape into the air by 

 means of a cock, and the communication between the boiler was fhut off. 



In thefc engines it may readily be apprehended that the adion of the dircifl; fteam on 

 any definite furface, fuch, for example, as a fquarc inch, will be accurately equal to the re- 

 a£tion of the water which is forced up; and confcqucntly, that Savery's engine will require 

 fleam more elaftic than the air of the atmofphere, in every cafe except that wherein the 

 water is raifed by fu£lion, and afterwards fuftered to flow out of the bottom of the vefl'el 

 into a clianncl or ciftcrn. But if this aflion of fteam be, by the intervention of fome me- 

 chanifm, tranfmitttd to the place where it is intended it ftiall operate, it will be pi^flible to 

 regulate the proportions in any defircd manner. It wus very early in the pre&nt century 

 I that 



