Volume 1

Petralogy. A treatise on rocks / By J. Pinkerton.

  • Pinkerton, John, 1758-1826.
Date:
1811
Catalogue details

Licence: Public Domain Mark

Credit: Petralogy. A treatise on rocks / By J. Pinkerton. Source: Wellcome Collection.

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    \ \ they spread in burning, is pungent, often fetid, and has no analogy with that of coal or bitu¬ mens. They burn with a clear flame, without bubbling or caking like coal, or running like so¬ lid bitumens. They leave powdery ashes like those of wood, but often in greater quantity, more ferruginous, and more earthy : they seem to contain a little potash These combusti¬ bles give an acid by distillation, which coal does not. Lignites vary in colour from deep and shining black, to an earthy brown: the texture of the greater part of the varieties indicates their origin, and gives rise to their name. The woody tissue is often observed, though sometimes it has wholly disappeared. The fracture of lignite is compact, often resiniform and coochoidal, or shining and straight. The external characters of the varieties of the species differ too much among themselves, to allow them to be farther generalised. 1. Lignite jetIt is hard, solid, compact, and capable of receiving a very bright polish; it is opake and of a pure black; its fracture is undulated, and sometimes shining like that of * M. Mojon found about 3 in 100 in the ashes of the bitu« minous wood of Castelnuovo. f Jet, Haiiy.—Pechkokle, pictform coal. Brock.'*