WATER. 



riments have led authors to think, that the prefTure, exerted 

 by fpouting water, was equal to the weight of a cylinder 

 of the fame diameter with the vein, and of the height of the 

 ■water above the hole. The ingenious author remarks that 

 he fpeaks only of Cngle veins of water, the whole of which 

 are received by the planes upon which they prefs ; for as to 

 the preffures exerted by fluids furrounding the bodies they 

 prefs upon, as the wind, or a river, the cafe is different, 

 though confounded with the former by writers on this fub- 

 jeft. Hydrodynamica, feci. 13. p. 289. 



M. Bernouilli endeavours to confirm his theory by a dif- 

 fertation in the eighth volume of the Afta Petropolitana ; 

 where he obferves, that the experiments formerly made be- 

 fore the Academy of Sciences at Paris, to eilablifh the 

 quantity of the prefTure exerted by a vein of fpouting 

 water, are very far from proving the truth of the rule they 

 are brought to eilablifh. For inflance, in one of thofe ex- 

 periments, the height of the water in the vefTel above the 

 hole from whence the vein fpouted was two feet Paris mea- 

 fure ; the diameter of the circular hole, which was cut in 

 the horizontal bottom of the vefTel, was four lines ; and the 

 force of the vein of water was obferved to be one ounce 

 and three-quarters. But the weight of a cylinder of water 

 of the diameter of the hole, and of the height of the water 

 in the veflel, is fcarce equal to one ounce and three -eighths. 

 The difference, therefore, is at leall three-eighths of an ounce, 

 which is about three-elevenths of the whole weight of the 

 before-mentioned cylinder of water. So that it is furprif- 

 ing, that this difference fhould have been afcribed to the re- 

 moval of the plane, receiving the impulfe, to fomc dillance 

 from the hole ; for this caufe, fuppofing the plane removed 

 to the diftance of two inches, could not produce an increafe 

 of one-fixtecnth of an ounce. It appears, therefore, that 

 the common opinion is rather overturned than confirmed by 

 experience. Du-Hamel, Hifl. Acad. Paris, ann. 1679, 

 feft. 3. cap. 5. 



M. Bernouilli, on the other hand, thinks his Own theory 

 fufficiently eftablifhed by the experiments he relates ; for 

 the particulars of which, we refer to the Afta Petropoli- 

 tana, vol. cit. p. 122, feq. 



This ingenious author thinks that his theory of the quan- 

 tity of the force of repulfion, exerted by a vein of fpouting 

 water, might be ufefully applied to move fhips by pumping ; 

 and he thinks the motion produced by this repulfive force 

 would fall little, if at all, fhort of that produced by rowing. 

 He has given his reafons and computations at length in his 

 Hydrodynamica, p. 293 to 302. 



The fcience of the preffures exerted by water, or other 

 fluids in motion, is what M. BernouilH calls hydraulico-Jlatka. 

 This fcience differs from hydroflatics, which confiders only 

 the prefTure of water and other fluids at refl ; but hydrau- 

 lico-flatics confiders the prefTure of water in motion. Thus 

 the prefTure exerted by water, moving through pipes, upon 

 the fides of thofe pipes, is an hydraulico-flatical confidera- 

 tion, and has been erroneoufly determined by many, who 

 have given no other rules in thefe cafes, but fuch as are ap- 

 plicable only to the prcffure of fluids at refl. See Hydro- 

 dynam. feft. 12. p. 256. feq. 



Water, Ra'ifing of. Machines for this purpofe are 

 fo numerous, that a minute dtfcription of fuch hydraulic 

 machines as are in common ufe would fill a volume ; and 

 a fcientific account of their principles, with the maxims 

 neceffary to be obferved in their conflruftion, would 

 form a very complete body of mechanical fcience : this is 

 far beyond the limits of an article like the prefent, in which 

 %vt can only introduce the moft flriking machines which 



have not already been explained in difl^erent articles of this 

 work ; and for others, we mufl refer to the original works 

 in which they are defcribed. 



The moft complete coUeftion of hydrauhc machines is 

 that of Jacob Leopold, entitled " Theatrum Machinarum 

 Hydraulicarum," publiflied at Leipzic, in 1724 and 1725, 

 in 2 vols, folio ; thefe form part of his voluminous " Thealii 

 Machinarum," which maybe confidered as containing all that 

 was known in mechanics at that period. 



M. Behdor, in his " Architefture Hydraulique," 1737, 

 has defcribed many machines which were invented fince the 

 date of Leopold's work. This eminent engineer was a 

 good mathematician, and his work may be confidered as a 

 ftandard for the theory of the hydrauhc machines of which 

 it treats. The " Experimental Philofophy" of Defagu- 

 liers contains fome chapters on hydraulic machinery, in 

 which he generally follows Belidor very clofely, but has 

 tranflated the mathematieal inveftigations of the former into 

 the ordinary procefTes of arithmetic, to adapt them to the 

 comprehenfion of mechanics ; and in this point of view, the 

 works of Defaguliers have been of great ufe. On the 

 other hand, M. Prony publifhed a modern edition of Beli- 

 dor's work in 1790, in which, in moll cafes, he has tran- 

 fcribcd the procefTes of the original into the modern modes 

 of analyfis ; but on the whole, he has added little to our 

 real knowledge, except his defcriptions and fuperb plates of 

 Mr. Watt's fleam-engine. 



We do not recoiled any complete coUeftion of machines 

 for raifing water fince Belidor, although the inventions of 

 the lafl century are both numerous and important. Much 

 information relative to them may be derived from Gregory's 

 " Mechanics," in 2 vols. 8vo. ; Dr. Robifon's Works, and 

 his excellent articles Hydrodynamics, Pump, and Water- 

 works, in the Encyclopaedia Britannica ; and from various 

 mifcellaneous publications, fuch as the Repertory of Arts, 

 and the Tranfaftions of different learned Societies ; alfo the 

 coUeftion of Mr. Smeaton's Reports, in 3 vols. 4to. It 

 is much to be regretted, that this excellent engineer never 

 completed a defign which he formed, to publifh a com- 

 plete coUeftion of praftical hydraulic machines founded 

 on his own experience. Among his manufcript papers which 

 have been lent to us by fir Jofeph Banks, we find an outline 

 for this work, of which we have availed ourfelves in this article. 



In confidering machines for raifing water, they may be 

 clafTed under two heads : 



Firft, thofe machines which aAuate fome kind of 

 bucket or vefTel adapted to contain water, which vefTel is 

 raifed up when full of water, and difcharges its contents 

 into an elevated refervoir, then defcends empty in order 

 to repeat its adlion : of this fpecies are, the buckets for 

 wells, fcoops, Perfian and Chinefe wheels, chaplets or 

 chains of buckets, the Noira, and the fcrew of Archimedes. 

 It is evident from the nature of all this clafs, that they are 

 incapable of raifing water to a greater height than that to 

 which the machine is elevated, or provided with tlie means 

 of drawing up the buckets or other vefTels ; and further, 

 that they cannot raife conflant ftreams of water, but that 

 the water mufl be given out by a fuccefliqn of difcharges 

 from the different buckets or vefTels. 



The fecond clafs comprifes thofe machines which aft by 

 means of valves and pillons moving in cyhnders, or other 

 equivalent contrivances, and force the water to afcend 

 through pipes or tubes : thefe machines have the advantage 

 of raifing the water to very great heights above the place 

 where the machine is placed. The greater part of thefe 

 machines we hafe already defcribed uiider the article Pump, 

 E Z anci 



