TO JUNCTION OF GRAND AND GREEN RIVERS. 85 



Vorde, facts of which the significance will be readily appreciated; but these are not 

 all the things that may lie seen from the vicinity of our present standpoint. The Mesa 

 Verde is, geologically, but a portion of the high table-lands which border the Upper 

 San Juan; the northern margin of which is followed by our route from the ford of the 

 Chama to the Mancos. I Fere this plateau terminates abruptly in a bold and most pic- 

 turesque wall, of which the general course, though varied by many salient and 

 re-entering angles, is nearly north and south from the Sierra de la Plata to the San Juan. 

 This mesa we completely encircled; examined it at a thousand points, and can speak 

 of its structure and extent with confidence. To obtain a just conception of the enor- 

 mous denudation which the Colorado Plateau has suffered, no better point of view 

 could possibly be selected than that of the summit of the Mesa Verde. The geologist 

 here has, as it seems to me, satisfactory proof of the proposition I have before made, 

 that, from the greater portion of the Colorado Plateau, strata more than 2,000 feet in 

 thickness ha.ve been removed by erosion. He here has a view toward the west, limited 

 only by the powers of human vision. 1 )irectly west the Sage-plain stretches out nearly 

 horizontal, unmarked by any prominent feature, to the distance of a hundred miles. 

 .There the island-like mountains, the Sierra Abajo and Sierra La Sal, rise from its sur- 

 face. South of these is the little doubled-peaked mountain, called by the Mexicans Las 

 Ort'JKK del Oso the bear's ears; beyond these his vision could not reach, but our 

 explorations enable us to tell him there lies the broad eroded valley of the Colorado, 

 bounded by two steps, of over 1,000 feet each, below the level of the Sage-plain, and 

 in the bottom of that valley, the chasm of the Colorado Canon, whose perpendicular 

 walls are 1, ">()() feet in height; beyond the trough of the Colorado, a plateau corre- 

 sponding to the Sage-plain, and beyond this a representative of the Mesa Verde. 

 Looking southwest, he would see the Sage-plain terminated in that direction by the 

 excavated valley of the San Juan; beyond this its representatives of similar character 

 and elevation; higher and more distant than these, the long perspective lines of the 

 lofty mesas north and west of the Moqui villages; the precise counterpart of that on 

 which he is supposed to stand. 



On the northern margin of the plateau, we are assured by those who have been 

 there that the constituent rocks of the Mesa Verde are exposed, holding the same posi- 

 tions as here Are we not then driven by these facts to conclude that, over all this 

 area of undisturbed sedimentary rocks, surrounded by table-lands composed of like 

 strata, presenting corresponding, but now widely separated faces, these strata once 

 stretched in unbroken connection; and that, from the great interval, where now wanting, 

 they have been removed by the same all-potent influence which has left such grand 

 and so similar records in tin; canons of the Colorado and its tributaries. 



The geology of the country lying between the Sierra La Plata and Sierra Abajo 

 is so monotonous as to require no lengthy description; all that need be said of it is 

 in brief notes of our different days' marches contained in my journal. From these I 

 make the following extracts: 



"Aitf/itxt \(}//>, (!<i>u/> 21, on ilio Dolores. The Rio de los Mancos is a clear mount- 

 ain stream, formed by two branches, which unite just below our camp, and which 

 rise in the foot-hills of the Sierra, de la Plata, on its western side;. Each of the two 



