E "^11 ] 



per cwt. of calx, and 30 of clay, of which the one-half is argill, 

 it would form one of the richeft forts of marles. The centefimal 

 proportions of this mixture fhould be, 



Silex -ai fciiJi 50 1 14=64. 



Argill - II t 8=19 



: V . Calx .?\^^Y^i\-\o vr 17 



100 



And in the troy pound, fuppofing the water, &c. to amount to 

 100 grains, the quantities will be, 



Silex - - 3622 



.... Argill - - 1075 



-. Calx - - 962 



5659 



O 



The fterility of this mixture feems to proceed from a defedl 

 of calcareous earth. If we fuppofe the marie poorer in that earth 

 the defeft will be ftill greater. The retentive powers of the dif- 

 ferent earths with refped; to water being expreffed by the quan- 

 tities which each can retain without fufFering any to drop, as 

 above faid, and the quantities retained by the mixed mafs of thefe 

 earths being proportional to the refpedlive quantities of each, 



Vol. V. Z it 



