[ 122] 
The fift and laft Part treats of the Pipes that are to con- 
vey Water, and of the Strength neceffary thereunto, and 
confifts of 3 Dilcourfbs, the firil whereof fhews the fize of 
Pipes requifite for the feveral expences of Water, proving 
that in fmall Pipes emptying the fame Water, the Water 
running fafter, has more fridion and is con (equently more 
retarded ; to avoid which this Rule is given, that the 
Squares of the Diameters of tlie Pipes be as the quantity of 
Water to be expended, in which cafe the W ater will run 
in all alike faft, and the friction be the fame; and when a 
great Pipe branches into feveral fmaller , diftributed to 
differing Jets , the fquare of the Diameter of the main 
Pipe muft be proportioned to the fum of all the Expen- 
ces of its Branches; and for a Foundation of a Calculm of the 
moft commodious fize of Pipes, 'tis laid down that for a 
Refervatory of 52 fuot high , whofe ishalfinlnch 
Diameter, the Pipe ought to be 3 Inches Diameter. The 
fecond Difcourfe Treats of the flrength of Pipes requifite for 
beating the weight of the Water, where are feveral pretty 
Experiments of the refiftance of Solides. The lafl of all 
gives amethodofdiftributing Water by Pipes into a City, 
and fhews how thofe Pipes are to be cleanfed from Mud,by 
leaving Apertures to let ,out the Water in thofe places 
where the pipes lie loweft ; and from Air, by the like Aper- 
tures left on the tops of thofe eminences where the 
Pipes pafs. 
N.B. That the Paris foot Meafure is to the London foot 
as 1 279, to 1 200, uiz. 79 Qentefmes of an Inch greater ; fo 
that to reduce the Experiments here produced,, "'tis to be no- 
ted that 14 Paris Pints, or 14 parts of 35 of the Cube of the 
Paris foot, is equal to J gall, 5 fints^ or 29 fints London 
Meafiire ; and fo much was evacuated in a minute through 
aBoreofaP^w Inch diameter, juft under the Surface of 
the Water ; but a Bore of a London Inda fo placed, will pais 
but,3 gall. I \ pint or 25 pints our Meafure in a minute 
at which rate near 7J Hogsheads will run through fuch a 
Bore in a Day. The 
