he columns that as the peat becomes heavier and
darker in color, it also becomes richer in carbon and poorer in oxygen.
Hydrogen varies but slightly.

As a general statement we may say that the ripest and heaviest peat
contains 10 or 12 _per cent._ more carbon and 10 or 12 _per cent._ less
oxygen than the vegetable matter from which it is produced; while
between the unaltered vegetation and the last stage of humification, the
peat runs through an indefinite number of intermediate stages.

Nitrogen is variable, but, in general, the older peats contain the most.
To this topic we shall shortly recur, and now pass on to notice--

_The ultimate composition of the compounds of which peat consists._

Below are tabulated analyses of the organic acids of peat:--

_Carbon._ _Hydrogen._ _Oxygen._
Ulmic acid, artificial from sugar 67.10 4.20 28.70
Humic acid, from Frisian peat 61.10 4.30 34.60
Crenic acid 56.47 2.74 40.78
Apocrenic acid 45.70 4.80 49.50

It is seen that the amount of carbon diminishes from ulmic acid to
apocrenic, that of oxygen increases in the same direction and to the
same extent, viz.: about 21 _per cent._, while the hydrogen remains
nearly the same in all.

b. _The mineral part of peat, which remains as ashes_ when the organic
matters are burned away, is variable in quantity and composition.
Usually a portion of sand or soil is found in it, and this not
unfrequently constitutes its larger portion. Some peats leave on burning
much carbonate of lime; others chiefly sulphate of lime; the ash of
others again is mostly oxyd of iron; silicic, and phosphoric acids,
magnesia, potash, soda, alumina and chlorine, also occur in small
quantities in the ash of all peats.

With one exception (alumina) all these bodies are important ingredients
of agricultural plants.

In some rare instances, peats are found, which are so impregnated with
soluble sulphates of iron and alumina, as to yield these salts to water
in large quantity; and sulphate of iron (green vitriol,) has actually
been manufactured from such peats, which in consequence have been
characterized as _vitriol peats_.

Those bases (lime, oxide of iron, etc.,) which are found as carbonates
or simple oxides in the ashes, exist in the peat itself in combination
with the humic and other organic acids. When