412 Cttnparifon of Steam-Eiighits. 



that Newcomen and Cawlcy began their trials of improvement of the Hcam-englne with a 

 cylindrical fteam-veflel and pillon dcprcffed by the weight of the atmofphere, by which means 

 they obtained a fafe application of power for raifnig water to heights far beyond any in which 

 the old engine could be trufted, on account of the extreme ftrcngth required in the boiler 

 and ftcam apparatus. This event is probably the caufe why fo little has fincc been done 

 to remedy that leading imperfe6lion, or to adapt the original machine to work itfelf 

 without an attendant. It is certain, however, that the weight of the apparatus, and fric- 

 tions of the parts, in all ftcam engines with a piflon and lever, have prevented their being 

 cxtenfively ufeful in fraall undertakings, fuch as the blowing of fmall furnace-bellows, the 

 drawing of boats and carriages, with numberlefa other operations where forces not exceeding 

 one, two, or three horfcs are wanted. In thefe operations it is highly probable that the 

 engine of Savery would be very ufeful, if it were made to work without an immediate attend- 

 ant ; for Dcfaguliers found the advantage greatly in favour of Savery's engine, on a fmall 

 fcale, compared with Newcomen's lever-engine. He had an engine of the former conftruc- 

 tion in his garden, which raifed ten tons of water an hour, about thirty-eight feet high ; 

 and a friend of his creeled a working model of the lever-engine on the fame fpot. The 

 boiler of this laft was exa£lly of the fame fize as that of Defaguliers, and his cylinder was 

 fix inches bore and about two feet in length. It raifed four tons per hour into the fame 

 ciftern. It coft three hundred pounds -, but the engine on Savery's conftrudion, having all 

 copper pipes, coft but eighty pounds. 



It muft not be overlooked, however, that this account affords no ftatement of the quan- 

 tity of fuel confumed under each boiler. It might perhaps have been the cafe, that Savery's 

 boiler could have fed a larger cylinder. But at all events there is no doubt of the fad, 

 that the beft lever-engines cannot be advantageoufly ufcd when linaller than a determinate 

 fize ; and that, on account of the charge of attendance to open and fhut the cocks, no trials 

 have been made to fliew upon how fmall a fcale Savery's engine might be rendered ufeful. 



An engine upon Savery's principle, with various judicious improvements, was ere£led four 

 years ago by Mr. Kier, at his manufadory of coach axle-trees near Pancras, where it has 

 almoft conftantly been worked without repair. It is perhaps on too large a fcale to afford 

 much information refpeCling this qucftion -, but is certainly of confiderable value, not only 

 becaufe it works without an attendant, and regulates its own motions, but alfo becaufe, as 

 might naturally be expeQed, the wear and tear is altogether inconfiderable. He has per- 

 mitted me to give an account of this engine. 



The (ketch Fig. 2. Plate XVII. reprefents this engine, without extreme pretenfions to ac- 

 curacy, but upon 2, fcale of a quarter of an inch to a foot. R reprefents an oval boiler 

 feven' feet long, five inches wide, and five deep. The proprietor confiders it as being of di- 

 menGons fufficicnt to work a larger engine ; a circuniftance which muft, in a certain degree, 

 diminilh the effccls of the prefent. It feeds itfelf in the ufual manner, with water conveyed 

 through a pipe at the end of which is a valve. This valve docs not open until the fall of 

 the water within the boiler has fuffered a float to fubfide, which by its adual weiglit allifts 

 to draw it open, but by its tendency upwards, as the water in the boiler rifes, fcrvcs effec- 

 tually to clofe it. The boiler, therefore, remains conftantly at or near the fame degree of 

 fullnef'.. The fteam is conveyed by a pipe TAV to a box B, through which, by tlie open- 

 ing and fliuiting of a valve, it can be conveyed to the working chamber E. The axis C 

 6 fervcs 



