SOILS AND ALKALI. 
7 
Schubler gives the weight in pounds of one cubic foot of 
dry soil: 
Sand,.110 
Sand and clay, ........ 96 
Common arable soil, . . . . 80 to 90 
Heavy clay,.75 
Vegetable mould,.-78 
Peat,.30 to 50 
Ordinary soils, under cultivation, have an average 
specific gravity of 1.2; when free from air, specific grav¬ 
ity about 2.5. 
The color of the soil depends exclusively on its com¬ 
position ; humus forming a nearly black soil, while sand 
gives a light yellow, and iron oxide produces a red color. 
The darker soils, other things being equal, have the 
highest absorptive power toward solar heat; this is shown 
when muck is applied to the surface of snow in the 
spring. 
The porosity of the soil is of the greatest importance 
in influencing the results of cultivation. It is a fully 
accepted fact that, other things being equal, soil is 
invariably most fertile which exists in the finest state of 
division, whose particles are the smallest. The finer the 
particles, the greater the surface exposed to the action of 
the dissolving medium. As plants assimilate food only 
from solutions, the importance of this statement can be 
estimated. A too fine state of division may cause the soil 
to become impacted. The structure of the soil should be 
such as to allow self-drainage. The water capacity of 
different soils has been very carefully determined by 
Meister. By water capacity is meant the ability to retain 
a definite quantity of water by absorption, without losing 
it or becoming super-saturated. 
As soils are rarely saturated with water, as there is in 
most cases an outlet at the bottom, Mayer lias shown that 
