175 D R IN KING POOL S. 7, 



of the valley (between the heights and the 

 morelandsj and winds alcng the (ide of the 

 oppofite fvvell to fome more elevated fonrce. 



If, when he arrive on the moreland hills 

 (orbv an obfervationfrom the top of the pre- 

 cipice) he firid that nature does not furnifli 

 the requiiite quantity of water high enough 

 to give the neceflary fall, the work is of 

 courfe impradlicable. 



In executing an artificial rill, opening a 

 ihallow channel, of a width proportioned to 

 the quantity of water to be conduced, is the 

 main operation. In mnkingflagnani pools we 

 have found that much art is necefTary to 

 make them retentive ; but in forming the 

 bed of a rill no fuch art is requiiite. It is 

 the nature of nintimz ''boater's to render the 

 furr'ace on which they run firm and retentive. 

 Sand is, I believe, the chief material ufed in 

 forming the channels of thcfc rills ; and this 

 only in places where an open rock or other 

 porou=i ftratum is croiied. 



Fvluch however depends on the quantity of 

 yVr//and the quantity of water. If the fall be 

 but little, and the quamity of water at the 

 fourcc be fuch as r.o': to admit of much wafle, 



great 



