PREFACE. 
No department of the natural sciences possesses 
greater interest, or leads to more important prac- 
tical results, than that of Geology. Of late years 
it has attracted almost universal attention, not only 
from the fascinating wonders it discloses, but also 
from its obvious and extensive application to the 
economical purposes of life. Of such importance 
has it been regarded, that many of our state legis- 
latures, as well as the general government, have 
authorized geological surveys to be made, in order 
that the natural resources of the country may 
be brought to light and fully developed. Every 
American must feel a degree of pride in reflecting 
that, in a short period, the geological features and 
mineral treasures of no country on the globe will 
be better understood or more justly appreciated 
than those of our own. Already have these sur- 
veys contributed millions in value to the produc- 
tive industry of the land ; and every year their 
importance is more and more demonstrated and 
acknowledged. 
To the young the study of geology is peculiarly 
attractive, as the objects of which it treats are ad- 
dressed to their observing faculties, which at this 
period are in a constant state of activity. For a 
long time this science was nearly a sealed book to 
