PART II. 



CHAPTER XIX. 

 DESCRIPTIVE GEOLOGY. 



PHYSICAL GEOGRAPHY OF NORTH AMERICA. 



Extent of North America. — Mountains. — Rocky Mountains.^ 

 Atlantic Series. — The Blue Ridge. — The Appalachian. — The 

 Alleghany. — The Eastern System. — Atlantic Plain. — Central 

 Basin.— Influence of Geological Structure on Society. — Influ- 

 ence of Geological Formations on Scenery. 



Physical Geography. — Before treating of the ge- 

 ology of this country, which our limits will only 

 allow us to do in a very brief and cursory manner, 

 it will be proper to notice some of its grand geo- 

 graphical features ; and, in doing so, we shall not 

 confine our attention to the United States, but em- 

 brace the whole of North America. This extends 

 through twenty-nine degrees of latitude and fifty- 

 eight of longitude, comprising a superficial area of 

 2,300,000 square miles, and having a frontier line of 

 10,000 miles in length, 3600 of which are seacoast 

 and 1200 lakecoast ; and a line drawn from the Pa- 

 cific to the Atlantic, in its widest part, would be 

 more than 2500 miles long. The portion at present 

 organized into state governments comprises an area 

 of 1,300,000 square miles. 



North America* is traversed by two great mount- 



* For much of the following chapter we are indebted to the 

 American edition of the " Encyclopedia of Geography," pub- 

 lished in Philadelphia, and the best work of the kind that has 

 ever appeared. 



