6 INTRODUCTION. 
gress of the mineral materials of the earth, 
through various stages of change and revolution, 
affecting the strata Avhich compose its surface ; 
and discloses a regular order in the superposi- 
tion of these strata ; recurring at distant inter- 
vals, and accompanied by a corresponding regu- 
larity in the order of succession of many extinct 
races of animals and vegetables, that have fol- 
lowed 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 Uttle regarded, and almost 
without a name, until the commencement of the 
present century ? 
Attempts have been made at various periods, 
both by practical observers and by ingenious 
speculators, to establish theories respecting the 
formation of the earth ; these have in great part 
failed, in consequence of the then imperfect 
state of those subsidiary sciences, which, within 
the last half century, have enabled the geologist 
to return from the region of fancy to that of 
