The Alamogordo Desert 165 



The strata of the lower carboniferous limestones now 

 confront us ; crystalline, enerinitic, and exceedingly hard, 

 rising often hundreds of feet sheer up and down. But 

 these dry walls likewise have their flora. MamiUaria 

 micromeris matches with its hoary spheres the weathered 

 stone or lights it up betimes with scarlet bloom, and 

 Notholcena serrata fills with sombre tufts every shattered 

 crevice. 



But the upper members of the carboniferous are much 

 softer and, amenable to erosion, present a gentler, flow- 

 ing topography. These slopes are everywhere clothed 

 with oak, not trees, indeed far from it; low dense shrubs, 

 the so-called shin-oak, Quercus gambelUi and Quercus 

 gunnisoni. These two species form pale green belts 

 around the mountains, and are recognized easily, distin- 

 guishable for miles. These species indeed form a sort 

 of phytographic border land; all below is desert; all 

 above is forest; for above stands, or lately stood, one of 

 the fairest bits of woodland in the United States, and 

 *that means in the world. But this forest is again in 

 large measure conformable to geologic structure, its dis- 

 tribution determined by the history of what lies beneath. 



As we ascend the mountain, passing all the carbon- 

 iferous limestones, sands, chalk-beds, and shales, we pres- 

 ently encounter the "red beds" already mentioned, the 

 most remarkable geological horizon in the country, fa- 

 miliar to every student of our central mountains, noted 

 even by the ordinary tourist, the same wherever found 

 in Utah, Colorado, the Black Hills of South Dakota, and 

 here again in these far-off mountains of the Mexican 

 border, the same vast gypsum-burdened deposits of clay 



