AMERICAN GEOLOGY. 
PRELIMINARY REMARKS. 
§ 1. The science of geology is of recent origin. The first 
attempts which were made towards the construction of a sys¬ 
tem, date no farther back than the middle of the last century. 
In its progress it has undergone many changes, as has every 
other science dependent upon observation and experiment. 
The object of geology is to give a rational explanation of the 
structure of the earth. To accomplish this, it examines the 
phenomena presented at the surface of the earth, and its interior, 
where it is accessible; and it attempts to discover the causes 
of those phenomena, and to find the true reason for their exist¬ 
ence, and also to fix the dates when remarkable changes 
occurred. The advantages resulting from the study of geology 
are numerous. It gratifies a laudable curiosity; it informs us 
where we may find the most valuable natural productions, as 
coal, salt, iron, gold, silver, manganese, copper, lead, marble, 
and many other useful substances; it enlarges our views of the 
field of nature; it enables us, by our knowledge of the present, 
to look far backward into the past; it reveals to us a vast dura¬ 
tion whose limit we can not fix—a succession of changes in 
the physical condition of the earth, which exhibit a progress 
towards an ulterior end which seems to have had reference to 
the existence and well being of man. We see in the earth’s 
changes, and its brute inhabitants, a progressive movement 
along an upward scale, not in a direct track, but rather in the 
ultimate results. It teaches us that order has prevailed in the 
operations of the natural elements through the lapse of ages— 
