NATURAL HISTORY. 4t 



transparent flint and nrpile; whilst, on tlte contrary* 

 coarse and impure fiint, by decomposing, passes to 

 potters earth without any intermedium. 



Our factious >!ass proves also the same alterations: 

 it decomposes in the air, and perishes in some degree 

 by remaining in the earth. At first its superficial scales 

 exfoliate ; by working it we perceive brilliant scales 

 fly from it ; but when its decomposition is more ad- 

 vanced, it crumbles between the fingers, and is re- 

 duced into a very fine white talcy powder ; and art 

 has even imitated nature in the decomposition of glass 

 and flint. 



CHAP. II. 



OF HILLS SEAS RIVERS AND LAKES THEIR NA- 

 TURE AND PROPERTIES. 



IF, in place of that beautiful variety of hills and val- 

 lies, of verdant forests, and refreshing streams, which 

 at present delight our senses, the earth were an even 

 and regular plain ; a dreary ocean would then cover 

 the whole globe, and it would be merely the habita- 

 tion of the scaly race. 



It cannot therefore be supposed, that even at first 

 the surface of the earth was perfectly regular ; and 

 since its first production, a variety of causes, the mo- 

 tion of the waters, the subterraneous fires, the wind, 

 and other external causes, have contributed much to 

 this irregularity. 



Next to the elevation of mountains, the depths of 

 the ocean form the greatest irregularities ; this depth 

 Ss very different even at great distances from land ; 



Vol. I. E 



