WATER. 



and when the valve fhuts again, the water falls with it, and 

 gives a fudden blow againft all the lides of the pipe. By 

 the lateral preffure, this force afts in a direftion perpen- 

 dicular to the fides of the pipe, vrith the weight of a pillar 

 of water whofe bafe is the feftion of the pipe, at the place 

 of the ftroke, and the height is equal to the whole height of 

 the water above that place ; and it llrikes with the fan:ie 

 velocity that the valve falls. Now if the firft ftroke of this 

 water makes the lead fwell outwards but the looth part of 

 an inch, the lead having no elafticity, will remain in that 

 pofition, and not (brink back; then fuppofe the next ftroke 

 fweUs the lead outwards the looth part of an inch more, the 

 diameter of the pipe will become fo much larger and remain (o. 

 The next ftroke will ftill make it jwider, and fo on for many 

 ftrokes, till at laft the lead becomes fo thin that it muft 

 break. This is inevitable if the force is great enough to 

 begin the enlargement, for after every ftroke the force of 

 the water ftriking will be greater than the preceding, in 

 confequence of the enlargement, and will foon burft the pipe. 

 An iron pipe is beft to be ufed, for even if it were in itfelf 

 as weak as the lead, it would not be liable to be enlarged, 

 although each ftroke ftiould make it yield, but by the 

 elafticity of the metal it would return again to its own 

 dimenfion after every ftroke. The fame will happen in 

 pipes of copper or wood, becaufe thofe fubftances are 

 elaftic. 



Wood pipes are made of elm or oak, bored through the 

 middle with a fucceffion of augres, increafing in fize until 

 the defired bore is attained. Behdor fays a man can bore 

 39 feet of elm pipe, two inches diameter, in a day, but only 

 65 feet of oak pipe. The manner of laying and joining 

 pipes is fully explained in our article Pipe. 



Care muft always be taken that wood pipes are bored in 

 the heart of the wood, and that the heart is of fufficient 

 thicknefs about the bore of the pipe. Elm pipes of nine 

 inches bore, that are from 80 to 140 feet beneath the fur- 

 face of the water in the refervoir, muft have the heart of 

 elm three inches thick after it is bored : therefore, a tree 

 muft be chofen of no lefs than 18 inches diameter in the 

 fmalleft part. For a depth from 60 to 80 feet, the heart 

 muft be 2i inches thick, which a tree of 17 inches in dia- 

 meter will afford ; for a depth of from 30 to 60 feet, the 

 heart mufl be two inches thick, and the tree 16 inches in 

 diameter ; and for any height under 30 feet, the heart need 

 be but \\ inch thick, for which a tree of i/), inches will 

 fufBce. ' 



From thefe proportions it may be determined what thick- 

 nefs the heart of elm fhould be for pipes of lefs bore at the 

 fame depths, taking it thinner in proportion to the diameter. 



Behdor recommends, in laying wooden pipes, to ufe a 

 compofition of mutton fat beaten in a mortar with powder of 

 brick -duft, fo as to make a fort of wax. When there are 

 cracks in the wood, fmall wedges wrapped with tow, and 

 covered with this compofition, are to be driven in to ftop 

 them. 



Earthen Pipes — M. Belidor ftates, that the beft kinds in 

 France are made at Savigny, near Beanvais ; they are in 

 lengths of two feet, which enter three inches into one an- 

 other, and are made of all diameters, from two to fix inches ; 

 when the pottery is feven lines thick, they will bear a co- 

 lumn of twenty -five feet of water. The joints are made of 

 a compofition of pitch, afties, and brick-duft with mutton 

 fat : this is applied hot ; but for larger pipes, a cement of 

 lime is ufed. 



One of the lengths of the pipes for the fupply of Edin- 

 burgh is made of pottery. 



Iron Pipes. — The methods of joining and laying iron 

 pipes will be found in our article Pipe ; but we ftiall 

 give a 



Table of the Weight of Iron Pipes caft at Carron Iron- 

 Works in 1769, being their Standard for dried Sand 

 Caftings, allowiog every 36 Cubic Inches of Caft Iron 

 to be equal to 10 lbs. 



It was afterwards found that, in a long courfe of praAice, 

 it was better to make iron pipes rather thicker ; becaufe in 

 moulding there is fome uncertainty if the metal is equally 

 thick all round. 



Water, Jets of, fountains were formerly the ornaments 

 of all garden and pleafure-grounds ; but are now fo far out 

 of faftvion, that we only iind them in the gardens of the 

 greateft palaces. | 



The moft celebrated are thofe of Verfailles and St. Cloud 

 in France, Frafcati, near Rome, and Peterhoff in RuiHa. 

 The fubjeft of the latter is the conteft of Jupiter with the 

 Titans ; it contains a column of nine inches diameter, which 

 fpouts fixty feet high. , 



The fountains of Verfailles, which are very numerous and 

 magnificent, are fully defcribed by Belidor. 



They confift of four grand pieces, which contain excellent 

 bronze ftatues, reprefenting fome fubjeft of the mythology, 

 befides a great number of jets for the ornament of fmalJer 

 pieces of fculpture. The bafon of Latona confifts of many 

 jets, which throw up water obliquely 30 feet high, into three 

 large bafons, from which it pours down in cafcades. The 

 water-piece of Neptune and Amphitrite eonfifts principally 

 of perpendicular jets, which are very numerous. The bafon 

 of Apollo contains the god in his chariot, drawn by four 

 horfes ; the great jets of this piece rife 57 feet, and the fmaller 

 jets 47 feet. The baths of Apollo contain moft excellent 

 fculpture, and large ftieets of water in cafcade. There are 

 alfo the pyramids of water, mountains of water, alleys of 

 water, theatre of water, &c. 



We have no room left for treating this fubjeft, which is 

 of fome intricacy, and (hall conclude with Mr Mariot's 

 table, which (hews the altitude of a refervoir necelTary to 

 produce a jet of a certain height ; and alfo the quantify ne- 

 ceffary to fupply jets of a certain bore, meafured in Paris 

 feet and Paris pints, 42.36 of which are equal to a cubic 

 foot Engh(h. 



