WATER. 



this at the fame time renders the valve lighter in the water, 

 and gives it a convex furface on the lower lide, which, when 

 tlie valve is opened, corrcfponds in curvature witli the in- 

 terior concave furface of the fpherical end ot the head of 

 the ram. The feat of the valve is compofed of a fliort 

 cyhnder or pipe, of which the opening is much greater than 

 the tranfverfe feftion of the body of the ram. This fhort 

 cylinder is fcrewed by its flanch into the opening in the 

 upper furface of the head qf the ram. This flanch of the 

 feat is fo formed as to liave an inverted cup round the upper 

 part of the fhort cylinder, that is, a circular channel or an- 

 nular fpace within the head of the ram, which will contain 

 air, and from which the air cannot efcape when the water 

 compreffes. The air in this channel is called the air- 

 matrafs. 



The fnifting-valve is at the end of a fmall pipe, which 

 leads from the annular fpace or matrafs to the open air. 

 The fnifting-valve opens inwards, in order to admit the air 

 to enter into the matrafs ; but to prevent its return, there is 

 another fmall valve in the fame pipe, which opens outwards : 

 the office of this is to admit a certain quantity of air into 

 the matrafs, and then to fhut and prevent any farther en- 

 trance. 



On the outfide of the feat of the ftop-valve that is over 

 the aperture in the liead of the ram, where the water ifTues, 

 another ftop-valve is applied, which is fimilar to the internal 

 valve before mentioned, but Ihuts down on the outfide of 

 the feat. Its ufe will be hereafter explained. 



The upper part of the pipe or head of the ram is made 

 flat at the part near the end where it enlarges to a fphere ; 

 and this flat furface on the top of the pipe has feveral nar- 

 row openings acrofs it, which are covered by as many flap- 

 valves of leather, to allow water to pafs out from the main 

 pipe, but to prevent its return. And on each fide of the 

 iiead of the ram, at the part oppofite to thefe flap-valves, is 

 a hollow enlargement, in form of a fegment of a horizontal 

 circle ; and the two enlargements taken together form a 

 circular bafon, through the centre of which the pipe of the 

 ram paffes ; but, as before ftated, the pipe, inflead of being 

 circular, is flat at top at that part, to form the feats for the 

 flap-valves. This circular bafon is covered by a cylindrical 

 air-veflel, fcrewed down by means of a flanch at the edge, 

 fo that tlie circular bafon forms the bottom of the fpace in 

 the air-veflel ; the flap-valves being covered by the_ air-veflel 

 are therefore within the veflel. 



In confequence of this arrangement, all the water which 

 idues from the body of the ram through the flap-valves will 

 flow off on each fide, and be received in the bafon ; but as 

 the circular bafon or bottom of the air-veffel is divided into 

 two parts, by the pipe of the ram which pafles through it, 

 there i.s a paifage communicating from one of the enlarge- 

 ments to the other ; for which purpofe, it curves down 

 and dcfcer.ds beneath the pipe of the ram ; and the afcend- 

 ing pipe that carries away the water which the machine 

 raifes, proceeds either from this curved paflage or from 

 fome other part of the bafon, fo that it may receive the 

 water which has paflcd from the body of the ram through 

 the flap-valves and the air-velTel into tlie bafon, at each fide 

 of the pipe. 



The aclion of this hydraulic ram is nearly the fame as the 

 preceding. Snppofc the pipe or body of the ram is full of 

 water, if the internal ftop-valve is opened, the water from 

 the refervoir will flow through the body of the ram, and 

 iffue through the opening at the end, it will lift up the ex- 

 ternal ftop-valve and efcape ; but the current having con- 

 tinued until the water has acquired a certain velocity, the 

 force of the current buoys up the internal valve, and clofes 

 Vol. XXXVIII. 



the paflage. The motion of the water contained in the ram 

 will thus be fuddenly arretted, and by its -vis inertia, or 

 moving force, will exert a fudden prefl"ure againft the ftop- 

 valve, and againft all the interior parts of the ram. The 

 fmall quantity of air contained in the fpace around the 

 interior ftop-valve, which is called the air-matrafs, is com- 

 prefled into a fmaller fpace, and, by its elafticity, takes off 

 the violence of the fliock or blow which would otherwife be 

 produced. This prefl'ure opens the flap-valves on the top 

 of the pipe, which are within the air-veffel, and a portion of 

 the water will be driven into the air-veffel, which is fup- 

 pofed to be fuU of air, compreffed or condenfed, till its 

 elafticity equals the preffure of the column of water which 

 is to be raifed up the afcending pipe by the atlion of the 

 machine. 



The water which is forced into the air-veffel caufes the air 

 therein to be condenfed, and to exert a greater degree of elafti- 

 city, until it will exceed the preffure of the column of water 

 in the afcending-pipe ; by degrees this air will therefore 

 force through the faid pipe all the water which was injefted 

 through the flap-valves, and caufe that quantity of water to 

 iffue from the upper extremity of that pipe. 



The moving force, or vis inertia of the mafs of water, 

 which was in motion in the body of the ram, having expend- 

 ed itfelf by forcing a portion of water into the air-veffel, and 

 making a ftill greater compreffion of the contained air, a re- 

 coil of the water in the body will take place with a flight 

 motion from the valve towards the open end of the body ; 

 this arifes from the reaflion or elafticity of the air contained 

 in the air-matrafs, and alfo of the metal of which the tube 

 is compofed. 



The flap-valves within the air-veflel ftiut, and prevent the 

 return of the water which has been forced into the air- 

 veffel. This recoil of the water in the body towards the 

 open end caufes a flight afpiration within the whole body of 

 the ram, and the external ftop-valve defcends by its weight, 

 and prevents the water with which it is covered from enter- 

 ing through it ; but the air paffes through the fmall pipe, 

 leading from the open air to tlie annular fpace or air-ma- 

 trafs, and opens the fnifting-valve, and a fmall quantity of 

 air is fucked into the matrafs ; but this is a very fmall 

 quantity, becaufe the external air-valve clofes as foon as the 

 air flows with a rapid current through the pipe and fnifting- 

 valve. 



During the recoil, the internal ftop-valve having nothing 

 to fuftain falls by its weight, and opens the paffage ; and as 

 foon as the force of the recoil has expended itfelf in afting 

 againft the column of water contained in the refervoir at the 

 open end of the body, the water begins again to flow 

 through the body in its original direction, and repeats the 

 aftion before defcribed. 



It fhuts the internal ftop-valve when it has acquired the 

 intended velocity, and being thus ftopped, the efflux of the 

 vis iiieylits condenfes the air-matrafs, and opening the flap- 

 valves, forces a quantity of water into the air-veffel, from 

 which the reaflion of the contained air will drive it up the 

 afccnding-pipe. 



The vis inerlin of the moving column of water being thus 

 expended, the recoil commences by the readlion of the air in 

 the matrafs, the flap-valves fhut, and tlie external ftop- 

 valve likevs'ife ; the afpiration produced by the recoil draws 

 fome air through the fnifting-valve, and it joins the air in the 

 matrafs. The internal ftop-valve falls open by its weight 

 and opens the paffage, fo that the water in the pipe can re- 

 fume its motion when the recoil has exhauftcd itfelf. 



The fmall quantity of air which is drawn into the ma- 

 chine through the air-valve, at each afpiration, caufes an acr 

 iK cumulation 



