Part 15

To determine accurately the ſpecies of earths is the moſt difficult part of mineralogy, for innumerable analyſes yet remain to be made. But that which now ſeems intricate and obſcure will become plain and eaſy when experiments have been ſufficiently multiplied.

CLASS III. INFLAMMABLES, OR BITUMINA.

§ 132.

To this head we refer all foſſils containing phlogiſton in ſuch great abundance, that under proper management they are inflammable. The Genera are obviouſly very few, and accurately ſpeaking there is only one Genus. But ſince phlogiſton is so very ſubtle as not by itſelf to become the object of our ſenſes, it will perhaps be adviſeable to conſider its more ſimple combinations as Genera: this has long been done ſo far as reſpects the metals, by univerſal conſent.

SULPHUR.

§ 133.

This name may be given to any acid coagulated by phlogiſton into a ſolid form. If all metals conſist of certain radical acids ſaturated with phlogiſton, as is highly probable, and with reſpect to arſenic is indubitably proved; then metals ought to find a place here. But until this theory be eſtabliſhed by numerous experiments, we ſhall only rank under this head the compounds which have not a metallic nature.

§ 134.

PHLOGISTON ſaturated with vitriolic acid.

CRONSTEDT, Min. § 151. Common Brimſtone. Sulphur.

§ 135.

PHLOGISTON ſaturated with aerial acid.

CRONSTEDT Min. § 154. A. plumbago. Black-lead.

The true compoſition of this has been detected by Mr. SCHEELE.

§ 136.

PHLOGISTON united to the acid of vitriol and of molybdæna; or what amounts to the ſame, ſulphur joined to the acid of molybdæna.

CRONSTEDT Min. § 154. b. c. Molybdæna. Molybdæna.

The acid of molybdæna has never yet been obtained quite free from phlogiſton (§ 32). If this acid be of a metallic origin, molybdæna is a mineralized metallic ſubſtance, and ſhould be placed with the other minerals.

PETROLEUM.

§ 137.

Phlogiston occurs alſo in the foſſil kingdom, combined in an oily form; but many ſuppose this derived from the vegetable kingdom.

§ 138.

PETROLEUM pure and ſelected.

CRONSTEDT Min. §§ 147–150. Naptha. Rock oil.

§ 139.

PETROLEUM joined to argillaceous earth.

CRONSTEDT Min. §§ 157–160. Lithantrax. Pit Coal.

§ 140.