hy the Mud of the Nile. 5*7 



both more in Number and of a greater Length than thofe that 

 are recorded by Herodotm% the Difference in the Meafure, 

 will give us the Difference in the Height of the Soil. Or, in 

 otherWords; if, m Herodotus" sT'nnQy fihcQn Grecian Cubits, at 

 /eafl, of Water, were required to prepare the Land for Til- 

 lage ; and twenty at kaB^ of much longer Cubits, are re- 

 ;quired at prefent ; the Land muft have received an Acceflion 

 of Soil in Proportion. Let us take then the Length of the 

 Cubit, made ufe of at prefent, to be xxi. Inches, or xxviii. 

 Digits only, inftead of (perhaps, what it will one Time or o- 

 ther be found to confift of,) fo many Inches. Yet even, upon 

 this low Computation, Egypt, by requiring at prefent cl. In- 

 ches more of Water to overflow it, than in the Time of Hero- 

 dotus, muft have gained, fmce that Time, the like additional 

 Height in if s Soil. 



But it is ftill obje6led, by this Author, (p. 15-1.) that no xherequi- 

 Computation can he ?nade how much the Soil has rifen, fromthl mTdocs 

 con/ider'mg how inuch the^'Ao, ought to rife for the Benefit of%ox,^^x?%^- 

 the Country. And this is fupported by alledging, that all this^^"^^^^' 

 defends on the Openings and Outlets there are for the Water ; 

 on their Breadth and their Depths ; on their being kept clean 

 or neglected. Now, in Anfwer to this, it may be obferved of 

 thefe Canals and their Outlets, in general ; that all they have 

 or can be fuppofed to have to do, at any Period of Time, or 

 upon any Occafion, is either to attend the Motion and to keep 

 up a conftant Height and Pace with the main Stream ; or elfe 

 by damming up their Mouths, they are to ferve for fo many 

 Bafons or Refervoirs, when the Inundation is over. When 

 therefore theWater, in thefe Canals, begins to ftagnate ; either 

 by being dammed up, or by being forfaken by the main Stream ; 

 (for the Beds of the Canals, by the eafier fubliding there of 

 the Mud, become frequently higher, if they are not kept 

 clean, than the Bed of the main Stream ;) in thefe Cafes, and 

 upon fuch Revolutions and Accidents, the Kile is no further 

 concerned ; it's Operation and Influence, at leaft with Regard 

 to thefe Canals, ceafe ; and Art and Labour begin then to take 

 Place. If then thefe Canals fhould or had at any Time been 

 too many in Number, or of too great Capacity, fo as to drain 

 off too much Water from the main Stream ; the Height of 



P Water, 



