I 178 ] 



it fhould feem that in fertile foils, where the fall of rain is from 

 20 to 30 inches, this power fhould not exceed 70 nor fall fliort 

 of 50 per cent. It were of great confequence to fettle this point 

 with precifion, but to do this would require more numerous ex- 

 periments. To explain my meaning I fhall give one example. 



Of the retentive Power of the fertile Soil mentioned by 

 Mr. Bergman. 



This foil contains, as we have already feen, Silex - 56 



Argill - 14 



Calx - 3,0 



Now the retentive power of 100 parts Silex = 25 



Argill =250 



Calx = 50 



Confequently the retentive power of 56 parts Silex =13 



14 — Argill=35 



30 — Calx =15 



63 



The conftitution of the Irifli fertile foils has not been afcer- 

 taincd, nor has the average annual quantity of rain been deter- 

 min;ed here ; indeed the folution of the queftion propofed by the 

 Academy does not ftridtly require it fhould, not having been 

 limited to any particular country ; but I fhould fuppofe its befl 



foil 



