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 twenty-one years after that a further discovery was made, which may indeed be said to have achieved a world-wide reputation.  It was found that, by adding bichromate of potash to a solution of aniline and sulphuric acid, a powder was obtained from which the dye was afterwards extracted, which is known as mauve.  Since that time dyes in all shades and colours have been obtained from the same source. Magenta was the next dye to make its appearance, and in the fickle history of fashion, probably no colours have had such extraordinary runs of popularity as those of mauve and magenta.  Every conceivable colour was obtained in due course from the same source, and chemists began to suspect that, in the course of time, the colouring matter