, some of which
was moving slowly down and some not at all. Grit can therefore be
separated from the rest of the soil by water.

This separation can be shown very well by the following experiment.
Rub ten grains of finely powdered soil with a little water (rain water
is better than tap water), and carefully pour the muddy liquid into a
large glass jar. Add more water to the rest of the soil, shake, and
again pour the liquid into the jar; go on doing this till the jar is
full. Then get some more jars and still keep on till the liquid is no
longer muddy but nearly clear. The part of the soil that remains
behind and will not float over into the jars is at once seen to be made
up of small stones, grit, and sand. Set the jars aside and look at
them after a day or so. The liquid remains muddy for some time, but
then it clears and a thick black sediment gathers at the bottom. If
now you very carefully pour the liquid off you can collect the
sediments: they are soft and sticky, and can be moulded into patterns
like clay. In order to see if they really contain clay we must do the
experiment again, but use pure clay from a brick yard, or modelling
clay, instead of soil. The muddy liquid is obtained as before, it
takes a long time to settle, but in the end it gives a sediment so much
like that from the soil, except in colour, that we shall be safe in
saying that the sediments in the jars contain the clay from the soil.
And thus we have been able to separate the sticky part of the soil--the
clay--from the gritty or sandy part which is not at all sticky. We may
even be able to find out something more. If we leave the soil sediment
and the clay sediment on separate tin lids to dry, and then examine
them carefully we may find that the {7} soil sediment is really a
little more gritty than the clay. Although it contains the clay it
also contains something else.

When the experiment is made very carefully in a proper way this
material can be separated from the pure clay. It is called silt, but
really there are a number of silts, some almost like clay and some
almost like sand; they shade one into the other.

If there is enough grit it should be weighed: we obtained 14 decigrams
of grit from 10 grams of our top soil and 17 decigrams from 10 grams of
bottom soil. We cannot separate the clay from the silt, but when this
is done in careful experiments it is found that the subsoil contains
more clay than the top soil. We sho