GEOLOGICAL SURVEY OF THE TERRITORIES. 201 



cated here. The second or upper level here, and also that bordering the 

 Costillo Valley, might be irrigated, thus increasing the breadth of the 

 arable area. Near the Bio Grande lie a succession of basaltic mesas" and 

 ridges, through which the Culebra and Costillo have cut channels for 

 their waters. The Eio Grande affords no bottom along this part of its 

 course, its waters being confined to a deep narrow cahon of basalt for 

 sixty-five miles, from La Joya to the crossing of the road to Conejos. 

 The Eio Colorado affords another valley of moderate width, which, like 

 the others, is broadest and most extensive at its upper end, narrowing 

 as it approaches the Eio Grande. Between this and the Taos Valley, 

 though a few spots of limited extent may be found which can be culti- 

 vated, the greater part is elevated and broken, and is covered with a 

 heavy growth of timber. 



The area west of the Eio Grande is similar in character to that east. 

 It is watered by Pintado Creek, Eio de Jara, and the Conejos Eiver, and 

 contains some as fine land as is to be found in the San Luis Valley. 



The valleys of the Pintado and de Jara are of but moderate extent, 

 traversing a more uneven country than that farther south. The Conejos 

 Eiver and its tributaries afford a valley which at its central part pre- 

 sents a broad and fertile area, where quite a number of Mexican settle- 

 ments have already been made. The southern portion of this side of 

 the San Luis Valley is principally an elevated basaltic plateau, or mesa, 

 which is covered with grass, and well adapted for grazing puri)oses, but 

 cannot be brought under cultivation, as it is beyond the reach of irriga- 

 tion. But there is on this side, as on the east, a large extent of land, 

 principally on the second level, which by proper efforts might be irrigated, 

 thus adding a broad margin to'the arable lands of this section. 



The soil of the lower valleys and bottoms throughout the section is 

 generally composed of a rich sandy loam, containing more or less com- 

 minuted marl. That of the upper levels and ridges has more or less gravel 

 and coarse sand mingled, with it. 



Having an elevation of seven thousand feet above the level of the sea, 

 and being partially surrounded by mountains, whose summits bear upon 

 them snow throughout the year, this basin must necessarily have a 

 tolerably cold climate. Yet the clays and the average temperature 

 during the growing season, as shown by the thermometer, would indicate 

 a more favorable climate than the surroundings do ; but this is to a cer- 

 tain degree deceptive, as the nights during the warmer half of the year 

 are quite cold as compared with the temperature of the days. And this 

 fact, as will be seen, has an important bearing in estimating the agricul- 

 tural capacity of this section. Frosts generally set in between the 1st 

 and 10th of September, but snow seldom begins to fall on the plain 

 until December, and the amount that falls during the winter is small. 



There is scarcely any portion of the valley that does not afford good 

 pasturage for cattle and sheep, and when every acre that can be irrigated 

 has been brought under cultivation, the higher ridges, mountain sides, 

 and elevated valleys will still furnish sufficient pasturage for numerous 

 herds and flocks; and if a means of reaching market is ever obtained, 

 few better places for the manufacture of butter and cheese than this can 

 be found. 



From Mr. Stephen E. Sterrett, who has been acquainted with this 

 valley for eighteen years, and has resided here for the last ten years, I 

 obtained the following information in regard to the crops. 



The principal products of the soil are wheat, oats, and potatoes, very 

 little corn being raised. Wheat is generally sown between the 1st of 

 April and 10th of May, and harvested from 1st to the 20th of September, 



