56 



PHYSICAL GEOGRAPHY. 



traverses our own continent. Mountains and hilly 

 ranges are not unfrequently parallel to each other; 

 and, when viewed on the great scale, they often en- 

 close vast tracts of country* within an irregularly 

 curved area. With respect to the shape of hills or 

 mountains, it is worthy of remark, that both sides 

 do not have the same degree of inclination : on one 

 side we generally find an abrupt escarpment, and 

 on the other a gradual slope ; so that the general 

 profile of any range, taken across the line of its di- 

 rection, would present the figure of a ridge-like 

 mass or a series of wedge-like masses ; a circum- 

 stance occasioned, in great measure, by peculiari- 

 ties of internal structure. It is a rare thing, more- 

 over, for mountains or hills to form isolated and 

 unconnected masses ; but, as already remarked, 

 they occur in ranges or chains, having a definite 

 direction, a considerable length, and a narrower, 

 but still considerable breadth. Smaller spurs or 

 branches are often thrown off into the surrounding 

 country, which again may have their minor branch- 

 es connected with them, the whole forming a regu- 

 lar and continuous system of valleys. 



* Burr's Practical Geology. 



