SOIL STUDIES
(See Soils by Fletcher.)
Soil should have a place in a Nature Study Course because:
1. It is so closely related to life.
2. It lends itself so admirably to the experimental method.
3. It is so liable to be overlooked and considered as common and valueless.
KINDS OF SOIL
Gravel is composed of small, rounded stones of various colours, sizes, and shapes. Occurs in beds, generally mixed with sand. Get a sample and examine the constituents. Lead the pupils to see that the pebbles are the result of the breaking up of larger rocks. What has made the corners smooth and rounded? What use is made of gravel? Have the pupils find some gravelly land.
Sand is composed of small angular pieces of hard rock. Have a few samples from different places brought to school, note fineness and colours, examine with a lens and note resemblance to pieces of broken stone. Draw a magnet through the sand and note black particles adhering, showing presence of iron in some form. Show the hardness by rubbing against the surface of a piece of glass. Sand is used for mortar, concrete, and glass. The chief sand-forming rocks are quartz and granite. Show pupils how to recognize these. Examine a sample of sand under a lens.
Clay. Note colour and odour of fresh sample. Dry and pulverize and note extreme fineness of the particles by rubbing between the fingers (an ounce of clay contains about four and one half million particles). Clay is made from crushed rocks, chiefly feldspars. Mix clay with a little water and note sticky character. Compare with sand in this respect. Which makes the best road in wet weather, gravel, sand, or clay? Note how hard the clay bakes after being moistened. Uses of clay—pottery, bricks, tile. Pupils should visit a brick- or tile-yard and watch the process of manufacture. In many parts of the world there are beds of clay of extreme fineness and whiteness, from which beautiful china is made.
Humus is decayed vegetable matter. Pupils should gather soil from the forest, bog, or marsh. Note dark colour. Examine carefully and see what you can find in it that is not in sand or clay.
Most of our farm land consists of these four soils mixed in various proportions, and it gets its name from the one that preponderates. Thus we have our sandy, gravelly, or clay loams. Humus is likely to be present in all fields, because vegetable matter grows, to some extent, everywhere; but freshly broken land, reclaimed swamps, and prairie lands are likely to be especially well supplied. The great value of humus in the soil will appear in later studies.