tO JUNCTION OP GRAND AND GREEN RIVERS. 117 



"September 22. To-day we ascended the mountain in search of a pass, and found 

 the base and flanks covered by the upturned sedimentary series, just as at Camp 50; 

 the Trias here, as at Laguna, 50 miles south, containing immense masses of snowy 

 gypsum, a thing rarely seen on the San Juan or Grand River." 



In the coarse yellow sandstones and conglomerates overlying the red beds of the 

 Trias I find large quantities of the sulphide of copper, replacing trunks and branches 

 of trees, just as at the "Cobre," near Abiquiu. 



The summit of the mountain where we ascended is over 9,000 feet above the sea; 

 it is covered with forests of yellow and sugar pine, Douglass spruce, and the western 

 balsam-fir,* interspersed with areas occupied by oak, maple, and aspen bushes, with 

 here 'and there poison-oak f and red-flowered locust. 



''September 23, Camp 51-52. Failing to find a pass across the mountain, we to- 

 day resumed our course southward, camping as before on a tributary of the Puerco. 

 The country is generally similar to that seen yesterday, but, as we descend, the forests 

 of yellow pine are gradually succeeded by scattered clumps of pifion, and red and 

 white cedar on the hills, the valleys grassy as before. We have also descended some- 

 what in the geological scale, our present camp being surrounded by mesas of the 

 great sandstone of the Animas the base of the Upper Cretaceous group with an 

 exposure of several hundred feet of the underlying strata given in the section of the 

 Creston, viz, gray shales, with bands of concretionary iron-ore, strata of yellow or 

 brown sandstone and beds of lignite, all Middle Cretaceous; in the shale beds is much 

 crystallized gypsum. 



"September 24, Camp 52 to 53. To-day our course has been southeasterly, ap- 

 proaching the southern end of the Nacimiento, through a region much like that of 

 yesterday, except that, as we have now penetrated deeply into the Middle Cretaceous 

 shales, the surface is less broken, the hills being rounded, with long, gentle slopes; the 

 timber has become more sparse, the country less picturesque and inviting. We have 

 here a fine view of all the interval between the Nacimiento and San Mateo. This was 

 apparently once occupied by an unbroken sheet of Cretaceous rocks, now for the most 

 part removed through the agency of the tributaries of the Puerco. In the west and 

 northwest, high mesas fill the horizon, forming the line of divide to which I have be- 

 fore referred. Around the base of Mount Taylor, extending many miles in every di- 

 rection, is a plateau of trap, which has apparently flowed from this great extinct vol- 

 cano, covering all the sedimentary rocks in its vicinity. In the open valley of the 

 Puerco stand many picturesque trap buttes, having a general resemblance to the 

 Needles of the San Juan. Of these the most conspicuous, called by the Mexicans the 

 Cabazon, resembles in its outline a Spanish sombrero, but is of gigantic dimensions, 

 being at least 1,500 feet in height. 



"South from the Cabazon is a high level mesa, composed of Cretaceous rock, 

 which forms the divide between the Puerco and the San Jose. This I have seen 

 from the other side on a former expedition. ,_ 



"September 25, Camp 53-54. To-day we crossed over the south end of the Naci- 

 miento Mountain to the pueblo of Jemez. The first part of our route was over the 



" I'itms ponderos, P. Lambertiana, Abies Douglasi, and Abies graiulix. 

 \Rhiis diversiloba and Ilobinia Xco Mexictina. 



