of another important product obtained from coal. Paraffin oil
and petroleum we obtain from coal, whilst candles, oils, dyes,
lubricants, and many other useful articles go to attest the importance of
the underground stores of that mineral which has well and deservedly been
termed the "black diamond."

CHAPTER VI.

HOW GAS IS MADE--ILLUMINATING OILS AND BYE-PRODUCTS.

Accustomed as we are at the present day to see street after street of
well-lighted thoroughfares, brilliantly illuminated by gas-lamps
maintained by public authority, we can scarcely appreciate the fact that
the use of gas is, comparatively speaking, of but recent growth, and
that, like the use of coal itself, it has not yet existed a century in
public favour. Valuable as coal is in very many different ways, perhaps
next in value to its actual use as fuel, ranks the use of the immediate
product of its distillation--viz., gas; and although gas is in some
respects waning before the march of the electric light in our day, yet,
even as gas at no time has altogether superseded old-fashioned oil, so we
need not anticipate a time when gas in turn will be likely to be
superseded by the electric light, there being many uses to which the one
may be put, to which the latter would be altogether inapplicable; for, in
the words of Dr Siemens, assuming the cost of electric light to be
practically the same as gas, the preference for one or other would in
each application be decided upon grounds of relative convenience, but
gas-lighting would hold its own as the poor man's friend. Gas is an
institution of the utmost value to the artisan; it requires hardly any
attention, is supplied upon regulated terms, and gives, with what should
be a cheerful light, a genial warmth, which often saves the lighting of a
fire.

The revolution which gas has made in the appearance of the streets, where
formerly the only illumination was that provided by each householder,
who, according to his means, hung out a more or less efficient lantern,
and consequently a more or less smoky one, cannot fail also to have
brought about a revolution in the social aspects of the streets, and
therefore is worthy to be ranked as a social reforming agent; and some
slight knowledge of the process of its manufacture, such as it is here
proposed to give, should be in the possession of every educated
individual. Yet the subjects which must be dealt with in this chapter are
so numerous and of such genera