h
peat, packing it as tightly as you possibly can, and then put it under
water and leave for some days. The peat becomes very wet and swells
considerably, overflowing the cup just like the clay did on p. 12.
After long and heavy rains peat in bogs swells up so much that it may
become dangerous; if the bog is on the side of a hill, the peat may
overflow and run down the hill like a river, carrying everything before
it. Such overflows sometimes occur in Ireland and they used to occur
in the north of England; you can read about one on Pendle Hill in
Harrison Ainsworth's _Lancashire Witches_. But they do not take place
when ditches are cut in the bog so that the water can flow away instead
of soaking in; this has been done in England.

This great power of absorbing water and other liquids, so terrible when
it leads to overflows, enables peat to be put to various uses, and a
good deal of it is sold as peat-moss, for use in stables.

[Illustration: Fig. 19. Cutting and carrying peat for fuel, Hoy,
Orkney]

In the ditches of a peat bog red slimy masses can often be found. They
look just like rusty iron, and in fact they do contain a good deal of
iron, but there are also a number of tiny little living things present.
The {40} stones and grit just under the peat are usually white, all the
red material from them having been washed out by the water which has
soaked through the peat. Then at the ditch these tiny living things
take up the red material because it is useful to them. Peat or
"moorland" water can also dissolve lead from lead pipes and may
therefore be dangerous for drinking purposes unless it is specially
purified. When you study chemistry you will be able to show that both
peat itself and moorland waters are "acid" while good mould is not.
That is why peat is not good for cultivated plants (see also p. 96).

Other things besides peat are formed when plants decay under water. If
you stir up the bottom of a stagnant pond with a stick bubbles of gas
rise to the surface and will burn if a lighted match is put to them.
This gas is called marsh gas. Very unpleasant and unwholesome gases
are also formed.

[1] The top two inches of soil only were collected here, and there were
many leaves, twigs, etc. mixed in. Soils from different woods vary
considerably. If the sample is taken to a greater depth the loss on
burning is much less, and may be only 5 or 6 per cent.

{41}

CHAPTER VI

THE PLANT FO