therefore, to discover and invent materials for supplying us with the
means of domestic heat and comfort, has exercised the ingenuity of man.
Those now known have been divided into five classes; the first
comprehending the fluid inflammable bodies; the second, peat or turf;
the third, charcoal of wood; the fourth, pit-coal charred; and the
fifth, wood or pit-coal in a crude state, with the capacity of yielding
a copious and bright flame. The first may be said seldom to be employed
for the purposes of cookery; but _peat_, especially amongst rural
populations, has, in all ages, been regarded as an excellent fuel. It is
one of the most important productions of an alluvial soil, and belongs
to the vegetable rather than the mineral kingdom. It may be described as
composed of wet, spongy black earth, held together by decayed
vegetables. Formerly it covered extensive tracts in England, but has
greatly disappeared before the genius of agricultural improvement.
_Charcoal_ is a kind of artificial coal, used principally where a strong
and clear fire is desired. It is a black, brittle, insoluble, inodorous,
tasteless substance, and, when newly-made, possesses the remarkable
property of absorbing certain quantities of the different gases. Its
dust, when used as a polishing powder, gives great brilliancy to metals.
It consists of wood half-burned, and is manufactured by cutting pieces
of timber into nearly the same size, then disposing them in heaps, and
covering them with earth, so as to prevent communication with the air,
except when necessary to make them burn. When they have been
sufficiently charred, the fire is extinguished by stopping the vents
through which the air is admitted. Of _coal_ there are various species;
as, pit, culm, slate, cannel, Kilkenny, sulphurous, bovey, jet, &c.
These have all their specific differences, and are employed for various
purposes; but are all, more or less, used as fuel.
The use of coal for burning purposes was not known to the
Romans. In Britain it was discovered about fifty years before
the birth of Christ, in Lancashire, not tar from where
Manchester now stands; but for ages after its discovery, so long
as forests abounded, wood continued to be the fuel used for
firing. The first public notice of coal is in the reign of Henry
III., who, in 1272, granted a charter to the town of Newcastle,
permitting the inhabitants to dig for coal. It took some
centuries more, however, to bring it into common use, as this
did not take place till about the first quarter of the
seventeenth century, in the time of Charles I. A few years after
the Restoration, we find that about 200,000 chaldrons were
consumed in London. Although several countries possess mines of
coal, the quality of their mineral is, in general, greatly
inferior to that of Great Britain, where it is found mostly in
undulating districts abounding with valleys, and interspersed
with plains of considerable extent. It lies usually between the
_strata_ of other substances, and rarely in an horizontal
position, but with a _dip_ or inclination to one side. Our cut,
Fig. 21, represents a section of coal as it is found in the
stratum.
[Illustration: _Fig_. 21.]