[ ^68 ] 



So lands that have a retentive or impermeable fubfoil fhould 

 be differently conflituted from thofe that have one lefs retentive 

 or more permeable. The time of the year in which rain moft 

 abundantly falls may alfo be w^orthy of notice. 



These circumftances muft undoubtedly modify the conclufions 

 that may be drawn from the experiments I fliall now relate. 



Analyfts of a fertile Soil in a very rainy Climate. 



Mr. Giobert has communicated to the public the analyfis 

 of a fertile foil in the vicinity of Turin, where it rains yearly 

 above 40 inches on the fquare foot. He found lib. of it to con- 

 tain from 20 to 30 grains of extradtive matter which flamed 

 and burned, and therefore was a coal foluble in water ; 26 lb. 

 of it contained 1808 grains of water. The fimple earths were in 

 the following proportion per cwt *. 



Hence the pound fhould contain f, 



grs. 

 Carbonic matter — — 25 



Water — — — 7° 



Silex, 



* Encyclop. Vegetation, 276. 



f The Turin medicinal pound is divided like the Troy, and contains the fame num- 

 ber of grains. 



