' CONTENTS. 



LETTER XII. 



Pafje 



In Answer, from Bovey... Present State of the Coal-pit at Bovey... Strata, &c 123 



LETTER XTII. 



Bitumens. ..Particular Kinds described. ..Known to Writers of the highest Antiquity. ..History of 

 Naphtha, Petroleum, and Asphalturn, from the more ancient Naturalists , 127 



LETTER XIV. 



Account of Bitumens continued, from more modern Authors... Ray, Dolomieu, &c....Tar Lake in 

 the Island of Trinidad. ..Petroleum Wells in the Burmha Dominions.. .Russia, &c.. 13$ 



LETTER XV. 



Amber. ..Known to the earliest Writers in Natural History... Jet. .. Succinum nigrum of the An- 

 cients.. .Cannel Coal... Difference between it and Jet......... 150 



LETTER XVI. 



Coal described. ..Different Kinds of Coal... Doubtful if known to the Greeks, or early Romans... 

 Brought into common Use, in this Island, but in modern Times... Found in various Parts of the 

 World ,. 159 



LETTER XVII. 

 Particularities observable in different Coal -pits... Cannel Uoal... Pyrites, &c 175 



LETTER XVIII. 

 Bituminous Fermentation... Com pared with the other Species of Fermentation. ..Bitumens, the 



Result of this Process... Peat, a vegetable Fossil, the first Product of this Fermentation 175 



LETTER XIX. 



Fossil Trees, imbedded in Peat, have undergone the bituminous Fermentation. ..The Changes 

 which mow-burnt Hay undergoes, somewhat similar to that produced by the bituminous Fer- 

 mentation . 189 



LETTER XX. 



Examination of Opinions respecting the Origin of Peat... Aboriginal Formation... A marine De- 

 posit... Mineral. Origin.. .Floating Islands 195 



LETTER XXI. 



The purer Bitumens, the Result of the same Fermentation by which Peat has been formed... 

 Bituminous Fermentation imitates, in its Result, the Operation of Secretion. ..Mineral Tallow, 



perhaps of animal Origin. ..Other Arguments in favour of bituminous Fermentation.., 206 



LETTER XXII. 



Of the Origin of the purer Bitumens. ..Naphtha. ..Petroleum. ..Mineral Tar. ..Mineral Pitch... 

 Asphaltum. .. Amber. ..Mellite... Jet and Cannel Coal... 218 



LETTER XXIII. 



Opinions respecting the Formation of Coal. ..Earth impregnated with Petroleum, the Opinion of 

 Buffon and Gensanne... Opinion of Sig. Arduino...Of Dr. Hutton and Professor PJayfair... Of 

 Mr. Williams.. .Of Mons. Tingry...Of Dr. Darwin. ..Ofi Mr. Kirwan...Of Mr. Hatchett...Of 

 Mons. Patrin...Of Mons. Fourcroy 235 



