OBJECTS AND METHODS OP GEOLOGY. 1 1 
of Mount Perdu, 10,378 feet above the level of the sea ; on the 
Andes they are seen at the height of nearly 16,000 feet, and 
around the sides of the Himmaleh mountains at a still greater 
elevation. In the United States they are of common occurrence, 
but generally at lower levels, as in the states of Kentucky and 
Tennessee, beneath the town of Wilmington and at other places 
in the low country of North Carolina. Petrified fishes and other 
marine animals are distributed, though more sparingly, throughout 
the surface of the globe. 
These remains of living beings, of which not only the individual 
has perished, but the race has been for ages extinct, prove that 
the existence of the earth has not always been marked by the 
condition of tranquility and repose in which we now behold it. 
They render it probable that the globe itself has been agitated by 
violent convulsions, and certain that it has been subject to revo- 
lution and change. They did not escape the notice and attention 
of the ancients,* but they were regarded with the less interest, 
because they were held by many not to be real remains, but imi- 
tative forms, produced by a certain plastic arid generative property 
residing in the earth, somewhat analogous to that which causes 
vegetables to spring up and grow. In succeeding times they were 
referred to a single catastrophe, (the deluge) to which we have 
the testimony of the sacred Scriptures, that the earth has been 
subjected. But it is now ascertained that this account of their 
origin is inadmissible. They are not merely scattered through 
the loose soil, but imbedded in the interior of solid rocks, occupy- 
ing an extent of hundreds of square miles along the sides or on 
the tops of mountains, and hundreds of feet in thickness. Such 
vast masses could not have been collected and consolidated within 
the space of less than a year, that the waters of the deluge covered 
the earth. The genera and species occupying the different beds 
placed in succession one above another are also different, by 
which it is further proved that the causes by which the condition 
of the globe has been changed, and the materials for the creation 
of ranges of lofty mountains, prepared and elevated into their 
present positions, have in more than one instance been active. 
The object of the second great branch of this science, sometimes 
denominated speculative or theoretical Geology, is — To discover, 
as far as possible, from the appearances presented by the rocks, 
beds of clay and sand, and the animal and vegetable remains that 
are imbedded in them, the nature of the causes by which they 
have been formed. It embraces therefore the primeval history 
of the earth, and an investigation of the number and kinds of the 
revolutions and changes to which it has been subjected, and the 
character of the agents by which they have been produced. 
4. Positive Geology may be regarded as a branch of Natural 
* Vidi factas ex aasquore terras 
Et procul a pel ago conchse jacuere marina?. 
Ovid Metamorph. Lib. xv. 263 
