FIG. 18.
Tumblers A and C contained moist sand, B and D contained puddled clay. Cuttings in B and D died, because there was not sufficient ventilation in the clay for root-development.[ToList]
CLASSIFICATION OF SOILS
Soil materials and soils are classified as follows:
Stones.—Coarse, irregular or rounded rock fragments or pieces of rock.
Gravel.—Coarse fragments and pebbles ranging in size from several inches in diameter down to 1/25 inch.
Sand.—Soil particles ranging from 1/25 of an inch down to 1/500 of an inch in diameter. Sand is divided into several grades or sizes.
- Coarse sand 1/25 to 1/50 of an inch.
- Medium sand 1/50 to 1/100 of an inch.
- Fine sand 1/100 to 1/250 of an inch.
- Very fine sand 1/250 to 1/500 of an inch.
These grades of sand correspond very nearly with the grains of granulated and soft sugar and fine table salt.
Silt.—Fine soil particles ranging from 1/500 to 1/5000 of an inch in diameter. It feels very fine and smooth when rubbed between the fingers, especially when moist. A good illustration of silt is the silicon used for cleaning knives, a small amount of which can be obtained at most any grocery store. By rubbing some of this between the fingers, both dry and wet, one can get a fair idea of how a silty soil should feel. Silt when wet is sticky like clay.