68 ABSORPTION FROM THE AIR. 



Kinds of Soil. ""'^X' 



Carbonate of lime in fine powder, 95.0 



Sandy clay, 94.0 



Stifflsh clay, 91.1 



Stiff clay, 88.6 



Pure clay, 81.7 



Garden earth, 85.1 



Humus, 84.6 



Absorption of moisture from the air. This is a 

 quality of great value, particularly in a hot and dry 

 country, where the amount of rain for several months 

 is very small. It restores to the soil a part of the 

 moisture which has escaped by evaporation. Sir 

 Humphrey Davy deemed this an index to the good 

 quality of land. It will be found, according to M. 

 Schlibler's experiments, that this property of the 

 absorption of moisture from the air is in proportion 

 to the fertility of the earth, since clay and peaty 

 soils possess it most abundantly, and sandy and 

 calcareous lands the least. Schiibler ascertained 

 the following facts by exposing soils to the atmos- 

 phere at the point of saturation with moisture, the 

 temperature being from sixty to sixty-five degrees 

 Fahrenheit. 



" Seventy-seven and one hundred and sixty-five 

 thousandths (77.165) grains of Troy weight of soil 

 spread upon a surface of one hundred and forty- 

 one and forty-eight one hundredths (141.48) square 

 inches, absorbed in twelve, twenty-four, forty-eight, 

 and seventy-two hours respectively, as shown in the 

 following table. 



