INTRODUCTION. 



11 



" From the high prames that rise in the back-ground, by a series of terraces 

 towards the spurs of the Eocky Mountains, the traveller looks down into an exten- 

 sive valley, that may be said to constitute a world of its own, and which appears 

 to have been formed, partly by an extensive vertical fault, partly by the long con- 

 tinued influence of denudation. 



" The valley is about ninety miles in length, and thirty in breadth, and stretches 

 away, westwardly, towards the base of the dark gloomy range of mountains, the 

 Black Hills. Its most depressed portion is about three hundred feet below the 

 general level of the surrounding country, and is covered by a soil, similar to that 

 of the higher ground, supporting scanty grasses. 



View of the Mauvaises Terres. — From the Geological Report of Dr. Owen. 



" To the surrounding country, however, the Mauvaises Terres present the most 

 striking contrast. From the uniform, monotonous, open prairie, the traveller sud- 

 denly descends, one or two hundred feet, into a valley that looks as if it had sunk 

 away from the contiguous world; leaving standing, all over the surface, thousands 

 of abrupt, irregular, prismatic, and columnar masses, frequently capped with irre- 

 gular pyramids, and extending to a height of one or two hundred feet, or more. 



" So thickly are these natural towers studded over the surface of this extraor- 

 dinary region, that the traveller threads his way through deep, confined, labyrin- 

 thine passages, not unlike the narrow irregular streets and lanes of some quaint 

 old town of the European continent. Viewed in the distance, indeed, these rocky 

 piles, in their endless succession, assume the appearance of massive artificial struc- 



