2 BULLETIN 211, U. S. DEPARTMENT OF AGRICULTURE. 



here mainly concerned with the details of the purely physical basis 

 of the industry, the factors of control and relation to other industries 

 are so closely connected with any proper kind of management that 

 they must be considered somewhat at length; and a study of range 

 conditions is but preliminary to an understanding of methods of man- 

 agement and the requirements necessary for the further improvement 

 of the*industry. 



THE TOPOGRAPHY OF NEW MEXICO. 



New Mexico is almost square in outline, being about 350 miles long 

 from north to south, nearly as wide at the southern end, and some- 

 what narrower along the northern boundary. Only the southern 

 boimdary is a broken line. The State consists essentially of a high, 

 arched plateau, the axis of the arch being near the middle and running 

 north and south, the northern end being higher than the southern. 

 This plateau is about 7,000 feet above sea level at its highest point on 

 the northern boundary line and drops to about 3,500 feet at its south- 

 ern end. 



Apparently resting upon this plateau, which is but a part of the 

 great Rocky Mountain uplift, are numerous mountain ranges that 

 seem to rise out of the sweeping plains as islands from the sea. These 

 mountains are of two fairly well-defined types — narrow, rocky ridges, 

 with but a scanty covering of low bushes and scattering trees, and 

 great mountain masses, consisting of numerous associated ridges more 

 or less densely covered with forests and woodland. Nearly all the 

 main ranges have a northerly and southerly trend. Some of the 

 mountains are composed of granites, rhyolites, gneisses, and other 

 igneous and metamorphic rocks, while many of them are great mono- 

 clinal piles of tilted, stratified rocks with sharp escarpment faces upon 

 one side. In actual altitude they range from less than 5,000 feet to 

 more than 14,000 feet, there being numerous peaks and ranges over 

 10,000 feet high. 



Large lava flows have occurred in several places, resulting in sheets 

 of black, vesicular basalt, covering extensive areas. Associated with 

 these flows are several large, extinct volcanoes and numerous small 

 cones. The lava sheets have done much to modify the relief features, 

 since. the lava (or mal pais, as it is locally known) is harder than the 

 underlying rocks and protects them from erosion. This has resulted 

 in a number of high mesas and buttes that almost take on the dimen- 

 sions of mountains. (PI. I, fig. 1.) 



The wide stretches of seemingly level plains that he between the 

 mountain ranges are nowhere really level. Many of them are typical 

 bolsons, or basins, into which drains all the water that falls in the 

 region. These bolsons are independent of each other and may occur 

 at any altitude (PI. I, fig. 2). The San Augustine Plains in central 



