TO JUNCTION OF GRAND AND GREEN RIVERS. 115 



the mountain, Douglas' spruce, yellow pine, the western balsam-fir, with thickets of 

 aspen, oak, maple, and red-flowered locust.* As we progressed we passed in succes- 

 sion over the upturned edges of all the sedimentary rocks seen on our route. 



1. The Upper Cretaceous sandstones and marls, but slightly inclined, and not 

 reaching within two or three miles of the mountain. 



2. The .Middle Cretaceous shales, forming a broad belt of (day-soil, from which 

 project here and there ledges of the harder strata, filled with tin 1 fossils characteristic of 

 this formation — Tnoceramus prdblematicuSj Gryphm Pitcheri, Osirea congestu, &c. 



.'). The Lower ( Yetaceous sandstones, from their hard and massive character, hav- 

 ing resisted erosion, are now forming hills and cliffs of considerable height 



4. The Triassic formation; its soft red marls, forming bare surfaces of blood-red 

 color, its sandstones standing out in strong relief, forming walls and palisades, often 

 nearly vertical, sometimes -10 or 50 feet in height, and only 5 or G feet in thickness. 



5. The Carboniferous series, mostly massive gray or whitish limestone, reaching 

 far up on tin; mountain sides, scarcely' at all metamorphosed, and filled with fossils. 



6. A central core or axis of red granite forming the great mass of the range. 



Our view from the summit was particularly fine. Immediately below us the dif- 

 ferent formations which 1 have enumerated were distinctly visible, running in parallel 

 bands along the mountain side. Home live miles north of our position the range falls 

 olf and disappears in the plain, but the line of upheaval is distinctly marked by an 

 arching of the unbroken sedimentary rocks. The upper part of the arch is removed, 

 and the surface-rock is a pure white sandstone, probably Triassic, beneath which the 

 "red beds" appear, forming on the east side of the mountain a beautiful rose-red valley. 



( )n the north we had a complete panorama of the mountains passed on our outward 



route, a view sweeping from the Santa Fe" and Taos Mountains to the Sierra de la Plata. 

 'Toward the west stretched a vast plain, deeply scored by many lines of erosion, of 

 which ('anon Largo may be taken as a type. 'This plateau — the San Juan division of 

 the great Colorado Plateau — Idled all the horizon, from the Sierra la Plata around to 

 San Mateo, the distant summits of the Carrizo and Chusca being just perceptible above 

 its surface. This greai Cretaceous plain sweeps up with nearly horizontal strata to the 

 base of the Xaeimiento; the series being most complete, the strata still horizontal, six 

 miles west of the mountain. At this point all the formations begin to rise toward the 



east ; their angles of elevation becoming greater as they approach the granitic axis, 

 where they are frequently quite vertical. The Nacimiento axis is here and farther 

 north the great divide between the waters of the Pacific and Atlantic, though, as before 



stated, the drainage of most of its western slope passes around the south end into the 



Puerco; the crest of the water-shed being formed by a line of high table-lands, which 



passes southwesterly between the head-waters of the ChaCO and the Puerco toward 



Mount Taylor (San Mateo). The line of upheaval which forms the divide at Camp- 

 bell's Pass, is widely different from the Xaeimiento axis, being indeed no other than 

 that of the Sierra Madre, which is entirely lost northward, as we saw no indication of 

 it on the San Juan. 



After leaving Camp 50, we made several days' marches southward, skirting the 



* Populut fremuloides, Quercu6 Oambelli, doer, up. Bobinia Neo Mexicans, 



