WATER. 



This Table is formed from obfervatioas of a great number 

 of engines of different powers, and making the intermediate 

 fizes to correfpond to the fame law of increafe. Thus, a 

 twenty-horfe engine is always made with a cylinder of 24 

 inches diameter, which is allowing 22.6 fquare inches of the 

 pifton's furface for each horie-power ; but larger engines have 

 a lefs allowance; an eighty-horfe engine has 19.8 fquare 

 inches to each horfe-power, and fmall engines have a much 

 greater allowance ; a ten-horfe engine having 245, and a 

 one-horfe, 28 fquare inches. This difference is to compen- 

 late for the numerous difadvantages which always attend 

 imall machines. 



The proper length of the ftroke for different engines is 

 not at all fettled. Mr. Watt's firfl engines were made 

 much longer than this Table, but of late years they have been 

 made fhorter, and without any adequate reafon which we can 

 perceive ; for it mud be an advantage to a machine to make 

 as few reciprocations as is confillent with a prafticable 

 length of cylinder. Thefe differences in the length of flroke 

 do not affoft the calculation of powers, becaufe if the 

 length of the flroke is altered, the number per minute is alfo 

 changed, and the velocity of the piflon is the fame ; at leall 

 it will be always nearly the fame as the Table for thofe en- 

 gines which work a crank and fly-wheel. But it muil be ob- 

 ferved that thefe engines move with a greater celerity than the 

 engines for pumping water, becaufe it is neceffary to accu- 

 mulate a conliderable velocity in the fly-wheel, or it mull be 

 immenfely heavy if the piflon was to move fo flowly as the 

 pumping engine generally does. 



It is ufual with engine-makers to calculate the velocity 

 of the piftons of engines at 220 feet per minute ; but we 

 liave rarely found them to come up to this in practice, and 

 have therefore calculated them at lefs. In the Table, the 

 preflure upon each fquare inch of the furface of the fteam- 

 piilon is in proportion to the velocities there marked ; and 

 if the velocities are found lefs than the Tabk, as is the cafe 

 with engines for pumping, then the load upon each inch of 

 the piflon mull be increafed in proportion, or elfe the power 

 of the engine will be different, although the cylinder re- 

 mains the fame. 



For inflance, the engine at the Birmingham canal, 

 mentioned in the article SrEA'si-Engiiie, had a twenty- 

 inch cylinder ; and being a lingle engine, fliould, by our 

 Table, be rather more than feven horfes power. How docs 

 this agree ? The weight raifed/cr hour to one foot high was 

 calculated, in the article STiiAM-Engitie, at 13,961,805 lbs.; 

 which divided by 60 gives 232.697 lbs. per minute : divide 

 this by 33,000, the horfe-power, and we have a feven- 

 liorfe power ; fo far it agrees with the Table. But the 

 preffnre on each fquare inch of the piflon was 1 1.7 lbs., and 

 the Table fays the preffurc fhould be 7.1 lbs. This dif- 

 ference is reconciled by the differences of the velocities ; for 

 the piflon of tlie Birmingham engine moved 635 feet per 

 minute, and the velocity in our Table for a fingle engine is 

 98 feet : now as 1 1.7 lbs. is to 7. i lbs., fo is 98 feet to 59^ 

 feet, inflead of 635: ; the difference is very fmall, and may 

 be thus accounted for. The Birmingham engine, although 

 feven horfes power, had only a twenty-inch cylinder, yet, 

 according to our Table, it fhould be 20.6 ; its piflon there- 

 fore required to move rather quicker, in order to make an 

 equal produce. Thus, the area of a twenty-inch cylinder is 

 314 fquare inches ; and of a cylinder 20.6 diameter, it is 332 

 fquare inches: now as 314 fquare inches is to 332 fquare 

 inches, fo is 59^ feet per minute to 63 feet per minute, inflead 

 "f ^37' which the engine attually moved. 



The allowance for fuel in this Table is as fmall as it will 

 ever be found to be in aftual pradicc ; the conlumptiou of 



fuel is not in dirccl proportion to the power of the engine, 

 becaufe fmall engines lofe more heat, and have more friftion 

 in proportion than large ones, and the reciprocations of the 

 motion are more frequent. We have taken the effeft of the 

 twenty-horfe engine at twenty millions of pounds of water 

 per minute, raifed one foot with each buflicl of coals weigh- 

 ing 84 lbs. ; this makes the confumptiou of fuch an engine 

 very near two bufhels per hour ; an eight-horfe burns one 

 bulliel. We have alfo taken the performance of the engine 

 of ICO horfes at 30 millions, and made all the intermediate 

 fizcs by a regular lav/ of increafe ; the refult agrees fo well 

 with feveral engines which we have obferved, that we con- 

 fidered the Table as very correct. The quantities of coal 

 are the fmallefl ; fcarcely any engines will do with lefs fuel 

 when they are working with their full load ; but many en- 

 gines will req\iire more. Engines vvill be conflantly found 

 which are of the dimenfions marked in our Table, and are 

 called fo many horfe-power, although they are working with 

 either a greater or leffer power than the Table expreffes ; 

 in fuch cafes, allowance of fuel mufl be altered in proportion. 



We have n«w gone through the defcription of thofe ma- 

 chines for r.iifmg water which are adluated by the mechani- 

 cal force of animals, or water or fleam afting externally by 

 means of levers and other connefting mcchanifm ; but there 

 are fome machines in which a current or a column of water 

 is made to operate within clofe veflels, and raife water to a 

 confiderable height : thefe are the Chremnitz fountain, the 

 fypho interruptus, and the hydraulic ram. Thefe are moil 

 admirable machines, particularly the lail, becaufe they are 

 fo hmplc, and having fcarcely any moving parts, are not 

 liable to decay and injury ; and they do not waite the motive 

 power in unnecefTary friftion and refiflance. 



The original fleam-engines of the marquis of Worcefter 

 and Savery, which are all of this clafs, are fully defcribed 

 under the article STSAM-Engine. The wafle of fuel in thefe 

 engines is fo great, that they fall very far below other en- 

 gines. We have mentioned the engine made by Mr. Kier, 

 which by a calculation will be found to raife only 2^ millions 

 of pounds of water one foot high with each bufhel of coals, 

 and the power of ilic engine is 25 horfes. An engine of the 

 fame kind, of five horfes power, which Mr. Smeaton calcu- 

 lated raifed 5 j millions, ^nd this is perhaps the utmofl of this 

 kind of engines. Another engine of 2f horfe-power, raifed 

 5-5 millions. The befl engine on Newcomen'a principle will 

 raife 10 m.illions ; Mr. Walt's 30 millions ; and Mr. Woolf '3 

 50 millions. From this ftatement, it is clear that the expence 

 of fuel m Savery's engines is lo great as to counterbalance 

 any advantages ariling from their fimplicity. 



The Chremnitz Maehine. — In this a column of water, de- 

 fcending from an elevated refervoir, is made to raife up an- 

 other column of water from a confiderable depth, and air is 

 introduced as the medium for communicating the preffure of 

 the motive column to that column which is to be raifed. 

 This machine is not a new invention ; its principle is fully 

 defcribed in the Italian book, "Le Machine," by Brancas 

 of Rome, 1629. A machine at Chremnitz, in Hungary, 

 is fo celebrated as to have given a name to this invention 

 from its lize, and the moll extraordinary formation of 

 ice and fnow by the working of it, befides that it is the 

 only one of the kind which had been applied to large works. 

 An account was given to the Royal Academy at Paris by 

 their correfpondent M. Jars, which is inferted in their me- 

 moirs for the year 1768 ; and Dr. Wolfe has alfo defcribed 

 it. The machine was executed by father Hell, a profeffor 

 of aftronomy at Vienna, in the year i 755 ; it is ufed to raife 

 the water in a Ihaft named Anialie, in the mines at Schrem- 

 nitz, or Chremnitz, in Hungary; fig. 14. Plate Wa- 

 ter- 



