Elastic Bitumen, or Fossil Caout-chou

Of the indurated Bitumens, one of the first we met with was included in coarse, somewhat earthy, elastic Bitumen, and much represented in form a gun flint, with fractures not unlike those in common flints. It proved extremely pure, of a dark olive green, and was closely surrounded by the other bitumen, as if it had been the fragment of a larger piece preceding in formation the earthy sort. We have since found a larger specimen of a similar nature, with a black outside—see the bottom figure, and also a small stalactite or lengthened drop. The smaller fractures in these show transmitted lights or illinitions of a warm yellow colour.

Thus it should appear that an accumulation of this yellow light, mixed with the black, gives the greenish hue to the substance. We suspect that these colours are more or less caused by the different degrees of oxygenizement of Iron.

Dull greens are seldom happily imitated by illuminators; thus, our figures may in this instance be rather too gay. According to the best chemists, Bitumen is formed principally of Hydrogen^† with more or less Oxide of Carbon, Oxide of Iron, and other incidental substances.