66 AFFINITY FOR MOISTURE. 



most are the least fertile. Pure sand has the great- 

 est specific gravity, and we know it to be sterile. 

 In proportion as it becomes light does the organic 

 matter, and therefore the fertility, increase. Hu- 

 mus, or soil of decayed vegetation, is the lightest of 

 all ; then clay, calcareous earths ; then sand. 



Mr. Johnston found one cubic foot of dry 



Silicious or calcareous sand to weigh .... 110 lbs. 



Half sand and half clay, 95 



Common arable land, from 80 to 90 



Pure agricultural clay, 75 



Garden mould, richer than the last in vegetable matter, 70 



Peaty soil, from 30 to 50 



Affinity for moisture. As the plant receives its 

 food through the medium of water, it is necessary 

 that arable land should have the power of imbibing 

 a considerable quantity. To be of value for fruits, 

 a soil should be able to absorb from forty to seventy 

 per cent, of its weight in water. Mens. Schiibler 

 made a series of very interesting and useful exper- 

 iments upon the character of soils, which was pub- 

 lished in the annals of French agriculture, and 

 whose tables we take the liberty to use, in consid- 

 ering this and other properties of soils. 



The degree of absorption in different kinds of earth is nearly as follows : 



rer cent, of Water 

 absorbed. 



Kinds of Earth. 



Silicious sand, 25.0 



Gypsum, 27.0 



Calcareous sand, 29.0 



Sandy clay, 40.0 



Strong clay, • . 50.0 



Fine calcareous earth, 85.0 



