This plays an important part in the formation of soils. It sweeps over the surface, taking away the moisture from it, and in dry weather the fine particles of dust and grit are borne from one place to another, together with leaves, twigs, and other organic material. Fresh surfaces are thus laid bare again for the action of rain, frost, snow, etc.

Variation of Temperature in Clayey, Sandy, and Chalky Soils.

----------Air Temperature.

----------Soil Temperature at I foot deep.

-------Soil Temperature at 4 feet deep.

Fig. 84. - Variation of Temperature in Clayey, Sandy, and Chalky Soils.

SALPIGLOSSIS (Three fourths natural size).

SALPIGLOSSIS (Three-fourths natural size).