If gypſum forms the matrix of any metal, it muſt be placed here.
Earths with Earths.
To this head belong moſt of the ſaxa (ſtones), enumerated by Mr. Cronſtedt, which form the immenſe bulk of mountains, and deſerve our particular attention, in order that, being better acquainted with the nature and ſtructure of the ſhell of the earth, we may be able to point out the coverings of minerals, and convert them all to our uſe.
Earths with Inflammables.
Lumps of mountain pitch are frequently connected with ſtones, and ſulphureous matters are found diffuſed through earthy materials.