uld of course expect this because
we have found that the subsoil is more sticky than the top soil. These
results are put into the columns as before so that we can now see at
once how much of our soil is water, how much can burn away, how much is
grit, and how much is clay and other things.

What would have happened if the sample had been dug out during wetter
or drier weather? The quantity of water would have been different, but
in other respects the soil would have remained the same. It is
therefore best to avoid the changes in the amount of water by working
always with 10 grams of _dried_ soil. The results we obtained were:--

Top soil Subsoil
Weight of dry soil before burning ... 100 100 decigrams
" " " after " ... 92 97 "
--- ---
The part that burned away weighed ... 8 3
Weight of grit from 10 grams of dried soil 17 19 "

The columns are given in Fig. 3.

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[Illustration: Fig. 3. Columns showing what 100 parts of dried soil
and subsoil were made of]

Summary. The experiments made so far have taught us these facts:--

1. Soil contains water, grit or sand, silt, clay, a part that burns
away, and some white chalky specks.

2. The top layer of soil to a depth of about eight inches is different
from the soil lying below, which is called the subsoil. It is less
sticky, easier to dig, and darker in colour. It contains more of the
material that burns away, but less clay than the subsoil.

3. When soil is dried it is not sticky but hard or crumbly; as soon as
it is moistened it changes back to what it was before. But when soil
is burnt it completely alters and can no longer be changed back again.

[1] See p. xiv for explanation of the figures in square brackets.

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CHAPTER II

MORE ABOUT THE CLAY

Apparatus required.

_Clay, about 6 lbs.; a little dried, powdered clay; sand, about 6 lbs.
Six glass jars or cylinders [2]. Six beakers [1]. Six egg-cups [1].
Six funnels and stands [2]. Six perforated glass or tin disks [2].
Six glass tubes [2]. Two tubulated bottles fitted with corks. Some
seeds. Six small jars about 2 in. x 1 in. [2]. Bricks. The apparatus
in Fig. 9. Pestle and mortar._

We have seen in the last chapter that clay will float in water and only
slowly settles down. Is this becau