EXCURSION TO THE ROCKY MOUNTAINS. 



PHYSICAL GEOGRAPHY OF THE REGION. 

 By (i. K. GttXBBRT. 



Tii .journeying three-fourths of the distance from the Atlantic to the 

 Pacific, the excursion crosses a number of distinct topographic prov- 

 inces, as well as districts characterized by a wide range of climatic con- 

 ditions. By way of introduction to the details described in subsequent 

 chapters, a few paragraphs will be devoted to the characterization of 

 the general physiographic and climatic types of the country to be trav- 

 ersed. 



The most general classification of the United States into physiographic 

 provinces indicates an Appalachian region at the east, a Oordilleran 

 region at the west, and a broad plain between drained by the Missis- 

 sippi and the St. Lawrence rivers. In the Appalachian region six belts 

 are distinguished— the Coastal plain, the Piedmont plain, the Blue 

 ridge, the Appalachian valley, the Appalachian mountains, the Cum- 

 berland plateau. They all trend approximately northeast and south- 

 west, and. as is the case with other physiographic provinces, they are 

 clearly differentiated in some districts and difficult of discrimination in 

 others. We are concerned chiefly with their aspects on the line of 

 journey. 



Washington City stands at the boundary between the Coastal plain 

 and the Piedmont belt. If any river on the Atlantic coast, from New- 

 Jersey to the Carolinas. be followed from its mouth, a cataract is sooner 

 or later reached and navigation interrupted. A line across the land 

 connecting these cataracts is known as the "fall line." and gives the 

 northwestern limit of the Coastal plain. The Coastal plain is charac- 

 terized by level strata, little indurat ed. having essentially the attitude 

 of deposition. These strata are Cretaceous and newer. The general 

 elevation is not great, and the northern portion of the plain is inter- 

 rupted by great tidewater hays, due to the sinking of the land and the 

 drowning of the river valleys. 



The Piedmont belt is in general a plain somewhat higher than the 

 Coastal plain, ami bearing small hills or even small mountains. Its 

 surface is generally undulating, and the greater lines of drainage are 

 abruptly incised. The plain is carved from indurated and folded 

 rocks of various ages, partly Jura Trias, but chiefly inetamorphic. On 

 (he outward journey the belt is crossed between Washington and 



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