[ 2' 2 ] 



bottom In a fubterraneous paiTage, marked 

 N, and flows out at O, where it appears a 

 common river, falling into the Irwe//, at P. 



The fubterraneous palTage N, was made 

 of that length, for a very material reafon ; 

 at O , is a communication between the end 

 of the paiTage and the furface of the water 

 above, in the nature of a fmalier well, but 

 the mouth plugged up; this is made with 

 deiign to clear the paiTage of all mud or 

 rubbiih that might accumulate in time at 

 the bottom of the well M, by drawing the 

 plug, and letting down a heavy fall of water, 

 to drive out fuch rubbiih at the mouth O. 



The reafon why the wear was made of 

 this form, was to command a greater line 

 of extent, within a fmalier general fpace 

 than if it was a plain circle, fquare, or other 

 iimple form. The circumference is three 

 hundred and fixty-iix yards, which was ne- 

 cefTarv for the quantity of water to be car- 

 ried off; now a circle of that circumference 

 could not be contained within the outward 

 bounds of the enlarged river, and at the fame 

 time leave fpace enough for a body of water 

 around it. 



The lines in the plan, marked R, R, de- 

 note a fubterraneous paflage, to drain off all 

 fuperfluous water at ibme houfes and ware- 

 houfes at S, S, and alfo from the above- 

 mentioned one at F. At T is a well and 

 plug, as before defcribed at Q^, for the 

 fame purpole of cleanfing the palf.ige from 



mud 



