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Obfervations. 113 tauch the appearance of bafalt, 6 Meta. Chin. Thorough black marble is vcry fcarce. Some black taarbles will not melt even by the aid of pure air, others will. Ehrm. § 210. Grey marbles, or limeftones, appear to be the lighteft. I found the fpec. grav. of a grey marble frorn Saxony only 2,700. It contained 42 per ct. of an ill Imelling fixed air. Pale red limeßones, I believe, are moflly d,olo- mites. One from Tiwdi in Finland afForded Mr. Georgi 96 per ct. of mild calx, 1 of filex, 1 of argill, and 1 of iron. It gave fire with fteel, effervefced with acids very flowly, and pre- fented a fra&ure like quartz. 1 Ad Petrop. 1782, 2761 Tellow orange marbles are much lighter; the fpec. grav. of that of Arragon is 2,678, of old Caftile 2,691, of that of Loyola 2,709, of that of Lamancha, which feerns compofed of mi- nute globules, 2,750, of the yellow marble of Sienna 2,677, Brijfon. It was found by Mr. Georgi tocontain 93 per ct. of mild calx, 3 filex, 2 argill, i magnefia, and 1 calx of iron. Green Marbles are faid to be very fcarce: according to Rinman, § 206, they derive their colour from Ihorl; hence they are generally fu- fible, Ehrm. § 210. The fpec. grav. of green campan'is 2,741. Blue, or deep blue, is certainly the rareft co lour among marbles ; that of Carrara, called Bar- diglio, has its fpec. grav. 2,713. The dove-co- lotired or greyifii blue is very common ; that of Goroiodfchit, in the Ouralian ridge of Cathari- nenburgh, contains by Mr. Georgds account 86 per ct. mild calx, 4 filex, 3 argill, 6 magnefia, and 1 calx of iron. I 2 Violet