WATER. 



cubic feet. Or, taking into the account the mtereft of 

 333,000/., the original expenfe of ereftion, which ij five 

 times as great as the annual expenfe, 1 1 cubic feet, which is 

 67 gallons, will coft three half-pence, or at the rate of a 

 farthing for 1 1 gallons. 



This is the account of it given by Belidor in his fecond 

 volume. 



Rannequin, the inventor, was an ingenious praftical mecha- 

 nic, but no mathematician or philofopher. In feveral pofi- 

 tions, the moving forces aft unneceflarily obliquely, which oc- 

 cafions a great lofs of power, and renders the machine lefs 

 effeftual. A great proportion of the whole moving power of 

 fome of the water-wheels is employed in giving a reciprocating 

 motion to the fets of rods and chains, which extend from 

 the wheels to the ciftern, nearly two-fifths of a mile diftant, 

 where they work a fet of pumps. 



As this machine is continually quoted as the moft power- 

 ful of all machines, we will compare its power with fome of 

 the large fteam-engines in England. The quantity of water 

 is (8484 -;- 60 = ) 141 cubic feet per minute x by 535 feet, 

 the height to which it is raifed, = 75649 cubic feet per 

 minute Kfted one foot high. Divide this by 528 cubic feet, 

 which is the quantity that can be lifted one loot per minute, 

 by what is called a horfe -power in fteam-engines = 143 

 horfe-power ; but as the machine afts by 14 water-wheels, 

 each one will be fcarcely lOj horfe-power. The horfe- 

 power is one-third greater than the average of horfes, and 

 we therefore eftimate that 215 horfes working together, 

 would do as much work as this machine ever did, or 15 

 horfes to each wheel ; but as the horfes could only work 

 eight hours /"i-r day, three fets mull be kept to continue 

 conilantly. 



M. Montgolfier informs us that the fupply of water to 

 the wheels is 138000 cubic feet per minute, and the fall is 

 45 feet ; this gives a power 8f times as great as the effeft 

 produced. Montgolfier found 22 j times when he tried it. 



The whole work is now in a very ruinous ftate, and many 

 projefts have been formed for a reftoration of the machine 

 on better principles. 



It is probable Rannequin thought his moving force would 

 not be fufficient to raife the water to the height of 535 feet 

 at once ; and this is agreeable to the praftice of more mo- 

 dern engineers. 



If the machinery was conftrufted in caft iron, in the fame 

 manner as fteam-engines are now made, the force of one 

 crank would be more than iufficient to raife a cylinder of 

 water of that altitude, and above eight inches in diameter, 

 without any complication ; but the pipes would require very 

 great ftrength. This is proved by a machine that has been 

 lately erefted at Marly, in place of one of the old water- 

 wheels. 



Even according to the original conftruftion, the water 

 might be raifed in one jet to the fecond refervoir. This ap- 

 pears from two experiments, one made in 1738, and the 

 other in 1775. In the firft, M. Camus endeavoured to make 

 the water rife in one jet to the tower ; his attempt was not 

 attended with fucccfs, but he made the water rife to the 

 foot of the tower, which is confiderably higher than the fe- 

 cond refervoir. During this experiment the machine was 

 fo much ftraincd, that it was found neceflary to fecure 

 fome parts of it with chains. 



The objeft of the fecond trial, made in 1775, was to 

 raife the water at once to the fecond lift, 346 feet. It did 

 afcend thither at different times, and in great plenty, but 

 the pipes were exceedingly ftrained at the bottom, fo 

 that feveral of them burft, and it was neceflary to fufpend 

 Vol. XXXVIII. 



and recommence the experiment feveral times. Thi» arofe 

 from, a fault which might eafily have been remedied ; vix. 

 from the age of the tubes and their want of ftrength ; 

 therefore it refults from this trial, that the chains which pro- 

 ceed from the river to the firft lift might be fuppreffed, to- 

 gether with the firft well itfelf : and this perhaps is all'that 

 is to be expefted without a complete change in the 

 machinery. 



Ruksfor calculating the Dimenfions of Pumps. — The quan- 

 tity of water defivered by any pump will be in the joint pro- 

 portion of the furface or bafe of the pifton and its velocity ; 

 for this meafures the capacity of that part of the working 

 barrel which the pifton paftes through ; and the fame is true 

 of feftor pumps, or rotative pumps : but as pumps with 

 ftraight cylindrical barrels are the only kind in general ufe, 

 it will be fufficient to give the rule for calculating the con- 

 tent of a cylinder, which is fimply to multiply the area of 

 the bafe by the length ; thus, take the diameter of the barrel 

 in inches, and the length of the ftroke in feet. 



Square the diameter in inches, and divide by 183.3 • multi- 

 ply this by the length of theflroke in feet, and it gives the con- 

 tent of the cylinder in cubic feet. 



Example — How many cubic feet of water will be raifed 

 in an hour by a pump 8^ inches diameter, and 3I feet 

 ftroke, which makes 18 ftrokes /ii;r minute ? 



Diameter 8.5 inches x 8.5 = 72.25 circular inches : di- 

 vide it by 183.3, wliich is the number of circular inches in 

 a fquare foot, and it gives .394 fquare feet for the area of 

 the barrel x 3.5 feet in length = 1.379 cubic feet; the 

 content of the barrel x 18 ftrokes ^^r minute = 24.822 

 cubic feet of water raifed /fr minute x 60 minutes = 1489 

 cubic feet per hour. 



If it is required to know the quantity which a pump will 

 raife in ale gallons, it is obtained by the following rule : 

 take the diameter of the barrel in inches, and the length of 

 the ftroke in feet. 



Square the diameter in inches ; multiply by the length in feet, 

 and divide by 30. 



This ftiould give the content of the barrel in ale gallons 

 of 282 cubic inches each ; but the rule is not perfeftly cor- 

 reft, for it affumes the gallon to be 282|-. 



Example of the fame Pump as above. — The fquare of the 

 diameter is 72.25 x 3.5 feet in length =: 252.875 -^ 30 = 

 8.429 ale gallons for the content of the barrel. The 

 true mcafure in this cafe is 8.45 gallons, which is very 

 near. 



To find the force rcquifite to work any pump, take the • 

 diameter of the barrel in inches, and the perpendicular height 

 of the column of water in feet. 



Square the iliameter in inches; multiply by .T^^ decimal, and 

 multiply by the height of the column in feet. 



This gives the force in pounds avoirdupois. It is ufual 

 to add one-fifth to this weight, on account of friftion and 

 refinance. 



Example. — Suppofe the above pump lifts the water 64 

 feet in the whole, what force will it take to draw up the 

 pifton ? 



The fquare of the diameter is 72.25 x .34lbs. =: 

 24.565 lbs., which is the weight of one foot high of tlie 

 column x 64 feet .— 1572 lbs., tho weight of the whole 

 column. Add 4th of this, wV.. 314 lbs. ..-r 1886 lbs. the 

 weight required to draw up the pifton and give it a proper 

 velocity. 



In conftrufting pumps, care niuft be taken to avoid all 

 unncceffary contraftions in the v.ilvcs or pipes which convey 

 the water. If the water-way is too fmall, the water will 



H be 



