le matter, and
appears to be thrown up in a liquid form by the volcanic energies which,
are still believed to be active in the centre of the lake, and which may
be existent beneath a stratum, or bed, of oil-producing bitumen.

In connection with the formation of this substance, the remarks of Sir
Charles Lyell, the great geologist, may well be quoted, as showing the
transformation of vegetable matter into petroleum, and afterwards into
solid-looking asphalt. At Trinidad is a lake of bitumen which is a mile
and a half in circumference. "The Orinoco has for ages been rolling down
great quantities of woody and vegetable bodies into the surrounding sea,
where, by the influence of currents and eddies, they may be arrested, and
accumulated in particular places. The frequent occurrence of earthquakes
and other indications of volcanic action in those parts, lend countenance
to the opinion that these vegetable substances may have undergone, by the
agency of subterranean fire, those transformations or chemical changes
which produce petroleum; and this may, by the same causes, be forced up
to the surface, where, by exposure to the air, it becomes inspissated,
and forms those different varieties of earth-pitch or asphaltum so
abundant in the island."

It is interesting to note also that it was obtained, at an ancient
period, from the oil-fountains of Is, and that it was put to considerable
use in the embalming of the bodies of the Egyptians. It appears, too, to
have been employed in the construction of the walls of Babylon, and thus
from very early times these wonderful products and results of decayed
vegetation have been brought into use for the service of man.

Aniline has been previously referred (p. 135) to as having been prepared
from nitro-benzole, or _essence de mirbane_, and its preparation, by
treating this substance with iron-filings and acetic acid, was one of the
early triumphs of the chemists who undertook the search after the unknown
contained in gas-tar. It had previously been obtained from oils distilled
from bones. The importance of the substance lies in the fact that, by the
action of various chemical reagents, a series of colouring matters of
very great richness are formed, and these are the well-known _aniline
dyes_.

As early as 1836, it was discovered that aniline, when heated with
chloride of lime, acquired a beautiful blue tint. This discovery led to
no immediate practical result, and it was not until twe