56 PRINCIPLES OF GARDENING. [CH. II. 



M. Schluber has more recently published experi- 

 ments upon this subject, and their results confirm 

 those of M. Humboldt. No earth, in the follo"«ing 

 table, absorbed any oxygen from the air in which they 

 were confined, so long as they were dr>'' ; but when 

 moist, and confined in a similar bulk of atmospheric 

 air for thirty days, they had absorbed its oxygen in 



the following proportions : 



Per cent. 



Siliceous sand l.G 



Calcareous sand 5.6 



Gypsum in powder . . . . 2.7 



Sandy clay 9.3 



Loamy clay 11.0 



Stiff" clay or brick earth . . . 13.6 



Grey pure clay 15.3 



Fine lime 10.8 



Magnesia 17.0 



Humus '20.3 



Garden mould 18.0 



Arable soil 16.2 



Slaty marl 11.0 



The decomposing parts of animals and yegetables 

 contained in a soil are also highly absorbent of mois- 

 ture : hence the more freely the air is exposed to 

 them, the more eff'ectually will they be enabled to 

 exert tliis power. By being freely exposed to the 

 influence of the air, such substances are more rapidly 



