158 GEOLOGICAL SURVEY OF THE TERRITORIES. 



stones of No. 1 appear now and then, especially in the vicinity of 

 Fort Union. Scattered all over this broad space are a vast number of 

 conical buttes and mesas, so that the surface would seem to be pierced 

 everywhere by dikes or outbursts of basaltic rocks. Since leaving the 

 Arkansas Eiver southward, the cretaceous formations seem to have in- 

 creased greatly in importance, and here ]^o. 2 seems to be enor- 

 mously developed. After leaving the Cimarron southward, a peculiar 

 configuration of the surface commences, which has been gradually un- 

 folding ever since we left the Spanish Peaks. From this x>oint to the 

 Cimarron there was a commingling of features, those that result from 

 the outpouring of the igneous rocks, and those from the weathering of 

 the tertiary strata. South of the Cimarron, the A'^allies are more narrow 

 and more sharply defined, as are the cones and mesas, and the only form- 

 ations involved, so far as the plains are concerned, are the igneous 

 rocks and the lower cretaceous. The grass is excellent in the vallies, 

 and the hills are covered with pifion. No good timber is found any- 

 where, so that the adobe method of building houses adopted by the Mex- 

 icans would seem to have arisen from the natural deficiencies of the 

 country. The mingling of the eroded material of the igneous rocks 

 with the cretaceous clays, sands, and marls, seems to have produced a 

 good soil. The vallies appear to have been carved out of the basaltic me- 

 sas, sometimes with wonderful regularity and beauty. There are sev- 

 eral sets or series of mesas, as it were. The higher mesas are covered 

 with a great thickness of basalt with vertical sides, the basalt breaking 

 into columnar masses. The lower mesas seem to be more level or table- 

 like, and are covered thickly with fragments of basalt. It is quite possi- 

 ble that these different mesas represent diifereut levels of the surface^ 

 X)rior to the outpouring of the fluid material. Between Sweetwater Creek 

 and Ocate, I found near the road some yellow sandstones, filled with 

 fragments of Ostrea, which I think belong to the upper part of No. 2. 



Near Ocate, the peculiar carving out of the valleys by erosion is seen, 

 presenting to the eye the most beautiful views that can be conceived 

 of in the natural world. They seem to have been formed by the hand 

 of art. No other condition of the surface could have admitted of their 

 existence. The fluid material seems to have been poured out over the 

 surface in one continuous and almost uniform sheet or layer, and these 

 valleys are thus carved out of the mesas. The little streams cut narrow 

 channels through these basaltic jilains, sometimes very deep and often 

 for miles without a bush to mark the water course, so that they are not 

 observed by the traveler until he is in close proximity to them. 



From Ocate Creek to Fort Union, the surface is covered with volcanic 

 rocks, many of which are so porous as to seem like pumice. These masses 

 are so light that they must have been scattered by the wind. There are 

 great numbers of hills and ridges scattered in every direction, covered 

 thickly with these igneous fr^agments. 



CHAPTEE IV. 



FROM FORT UNION TO MORA. 



Through the kindness of Dr. Peters, United States Army, the surgeon 

 of Fort Union, I made a short journey to Mora Valley, about eighteen 

 miles west of Fort Union, and I am also indebted very much to him for 

 his knowledge of this country. 



