1() INTRODUCTION. 



and silver, tin, copper, lead, and zinc ; in another series, we 

 find beds of coal ; in others salt and gypsum ; many are 

 composed of freestone, fit for the purpose of architecture ; or 

 of limestone, useful both for building and cement ; others of 

 clay, convertible by fire into materials of building, and pot- 

 tery : in almost all we find that most important of mineral 

 productions, iron. 



Again, if we look to the great phenomena of physical geo- 

 graphy, the grand distributions of the solids of the globe; 

 the disposition of continents and islands above and amidst 

 the waters; the depth and extent of seas, and lakes, and 

 rivers; the elevation of hills and mountains; the extension of 

 plains; and the excavation, depression, and fractures of val- 

 leys ; v>^e find them all originating in causes which it is the 

 province of Geology to investigate. 



A more minute examination traces the progress of the 

 mineral materials of the earth, through various stages of 

 change and revolution, affecting the strata which compose 

 its surface ; and discloses a regular order in the superposi- 

 tion of these strata ; recurring at distant intervals, and ac- 

 companied by a corresponding regularity in the order of 

 succession of many extinct races of animals and vegetables, 

 that have followed one after another during the progress of 

 these mineral formations ; arrangements like these could not 

 have originated in chance, since they afford evidence of law 

 and method in the disposition of mineral matter ; and still 

 stronger evidence of design in the structure of the organic 

 remains with which the strata are interspersed. 



How then has it happened that a science thus important, 

 comprehending no less than the entire physical history of 

 our planet, and whose documents are co-extensive with the 

 globe, should have been so little regarded, and almost with- 

 out a name, until the commencement of the present cen- 

 tury ? 



Attempts have been made at various periods, both by 

 practical observers and by ingenious speculators, to esta- 



