Definition of "bitumens"

Moſt naturaliſts and chemiſts aſcribe the formation of petrolea to the decompoſition of ſolid bitumens by the action of ſubterraneous fires.

1796, Antoine-François de Fourcroy, Elements of Chemistry, and Natural History: To which is Prefixed the Philosophy of Chemistry, page 209

Thus, as I have shown that there is a sort of gradation from naphtha to asphaltum, through a series of undefinable petrolea, so this analogy may be extended to the next general variety of the bitumens, coal.

1977, The Philosophical Magazine, page 212