SAND AND CLAY 321 
Clay is made up of exceedingly fine particles which 
readily bind together when wet; hence when moist it is 
plastic and can easily be moulded into any shape—is 
compact, feels smooth and greasy ; when dry, adheres to 
the tongue, is hard and permeable to water which it 
readily absorbs; when saturated, becomes impermeable 
to water; retains moisture for a long time ; when burnt, 
becomes hard and porous, readily absorbing water which 
passes through without softening the material ; is derived 
from the disintegration of rocks; settles down slowly in 
water. 
Note :—The work should of course be dealt with in such a way 
that pupils will be led to find out for themselves the properties of 
the two substances. The methods of treatment necessary for this 
result will readily suggest themselves to the teacher. 
KINDS OF SOIL. 
Soils rarely consist of one constituent only—nearly all 
soils being made up of varying proportions of sand, clay, 
lime, and humus. As, however, sand and clay occur in 
much greater quantities than any of the other constituents, 
it has been found convenient to classify soils according to 
the amount of these substances they contain—thus if the 
soil consisting almost entirely of sand and clay contains 
about 90 per cent. by weight of sand, it is said to bea 
sandy soil. If from 10 to 40 per cent. of clay, it is a 
sandy loam; if from 40 to 70 per cent. of clay, it is a 
loamy soil ; if from 70 to 85 per cent. of clay, it is a clay 
loam ; if from 85 to 95 per cent. of clay, it becomes a clay 
soil. — 
Note :—A loam may be defined as a soil consisting of sand 
and clay, in which there is an appreciable amount of both 
constituents. 
X 
