TO JUNCTION OF GRAND AND GREEN RIVERS. 8L> 



C II A I J T K R 



GEOLOGY OF THE SAGE-PLAIN AND VALLEY OF THE UPPER COLO- 

 RADO. 



GENERAL FKATURES op THE NORTHERN PORTION OF THE COLORADO BASIN ASPECTS AND 



STRUCTURE, OF THE SAGE PLAIN MESA VEHDK ENORMOUS DENUDATION OF THE COLO- 

 RADO PLATEAU CROSSING THE SAGE PLAIN Rio DE LOS MANGOS RioDoLORES SECTION 

 OF LOWER CRETACEOUS ROCKS RUINS ON THE DOLORES Si EUR A SAN MIGUEL SUROU- 



ARA TlERRA 1JLANCA GlTA.TELOTES CANON PINTADO TRIASSIO ROCKS SAURIAN BONES 



LA TENEJAL ERODED BUTTES CASA COLORADO Ojo VERDE SIERRA LA SAI EXCUR- 

 SION TO GRAND RIVER CANON COLORADO PLATEAU BORDERING THE COLORADO RIVER 

 ERODED MONUMENTS LABYRINTH CANON RUINED BUILDINGS SUMMIT OF THE CARBON- 

 IFKROUS FORMATION SECTION OF TRIASSIC ROCKS REMARKABLE COUNTRY ABOUT THE 

 JUNCTION OF GRAND AND GREEN RIVERS SINGULAR ERODED BUTTES AND PINNACLES 

 NETWORK OF CANONS CANON OF GRAND RIVER SECTION OF CARBONIFEROUS STRATA 

 TRANSVERSE SECTION OF THE COLORADO VALLEY RETURN TO SAGE-PLAIN JOURNEY 

 SOUTHWARD TO THE SAN JUAN SlERRA ABAJO. 



Uetween the Rio dela Plata and the Rio de los^ Mancos we skirted the base of the 

 extreme southern point of the Sierra de la Plata. These mountains terminate south- 

 ward in a loiiy slope, which falls down to a level of about 7,500 feet above; the sea 7 

 forming a plateau which extends southward to the San Juan, the Mesa Verde, to which 

 T shall soon have occasion again to refer. This mesa terminates on the west by an 

 abrupt nearly vertical precipice from 1,"20) to 1,500 feet in height. Between the mesa 

 and the mountains is a natural pass or jitu'rfu, through which the Spanish trail leads 

 where it crosses the divide. On the west this puerta opens to the right and left; 

 bounded on the north by the retreating southwesterly slopes of the Sierra de la Plata, 

 on the south by the wall-like edges of the Mesa Verde. As we stood on its threshold 

 \ve looked far out over a great plain, to the eye as limitless as the sea; the monotonous 

 outline of its surface varied only by two or three small island-like mountains, so distant 

 as scarcely to rise above the horizon line. Here we were to leave the lofty sierras of 

 the Kocky Mountain system, which had so long looked down on our- camps and marches, 

 the picturesque scenery of the foot-hills, their flowery valleys and sparkling streams, 

 the grateful shade of their noble forests, and take our weary way across the arid ex- 

 panse of the great western plateau; a region whose dreary monotony is only broken by 

 frightful chasms, where alone the weary traveler finds shelter from the burning heat of 

 a cloudless sun, and where he seeks, too often in vain, a cooling draught that shall 

 slake his thirst, To us, however, as well as to all the civilized world, it was a terra 



