Meafurement of a Bafe on Hounflow-Heath. 415 
order two fuch pipes to be provided, about fix feet in length 
each, and one foot in diameter, with a bore of four inches in 
the uppermofl end, for the depth of two feet, and crofs-arms 
near the Iowermoft end, in the file of the common warping 
pofts. As an improvement on this idea, Mr. Mylne very 
judicioufly propofed that, inftead of the crofs-arms, the lower 
ends of the pipes fhould pafs through the nave of an old 
coach-wheel, and then be fecured by a bolt underneath. This 
alteration was approved of ; and the machines, thus executed, 
were lent foon after by water to Hampton. 
The plan and feflion of one of thefe wheels, with the 
difhed fide downwards, are reprefented towards the left-hand 
in tab. XVIII. where it will be perceived, that by means of 
four knee-pieces, made of crooked oak, the pipe is firmly 
bolted to the wheel, and thereby kept at right-angles to its 
plane. The top of the pipe is alfo fecured exteriorly by an 
iron hoop, and has a cafl-iron box driven into it, whofe inner 
diameter is four inches, anfwering to that of the bore. Four 
oak piles for each wheel were prepared to be driven into the 
bottoms of the pits dug for their reception, which were fix feet 
in diameter, and the fame in depth. The foil near Hampton 
Poor-houfe being of a loofe fandy nature, there the piles were 
eafily driven into the bottom, until their tops were on the fame 
level. The flat of the fellies of the wheel being then laid on 
the piles, the earth was filled in and well rammed around the 
pipe, quite up to the furface, with which its mouth is even. 
But the foil at King’s Arbour, being a hard-bound gravel, the 
piles could not be driven into the bottom of that pit ; where- 
fore, the flat of the wheel refs there on the gravel only. 
The brafs cup, formerly defcribed, was from the firfl in- 
tended to be placed in the pipes, for which purpofe it has two 
Vol, LXXV. I i i lids ; 
