DESCRIPTIVE GEOLOGY. 681 



the side ravines are cut through loosely cemented gravel hills and mesa like 

 elevations extending between the southwest and southern slopes of the Eagle 

 Mountain group and the southern outrunner of the Quitman Mountains, 

 which consist of, or at least are flanked and capped by, metamorphic sand and 

 limestone and partly decomposed shales similar to those found in and west of 

 the Eagle Mountains. The flat on the east side of the Eagle Mountains, 

 which is also level and to the greater part covered with fertile soil, in its 

 northern extension terminates toward the Rio Grande in rugged gravel hills 

 and elevations between the southeast foothills of the Eagle group and the 

 Van Horn Mountains, and is similar to the flat west of the Eagle group. 

 The igneous rocks of the Van Horn Mountains disappear about two miles 

 south of Van Horn Wells below a capping of stratified rocsk, flanked on the 

 west side by moderately altered limestone hills. I have not yet had the op- 

 portunity of determining their age. 



A spur of the Van Horn Mountains branching off about ten miles south of 

 Bass' Canyon in a northwesterly direction shows strongly micaceous granite 

 breaking through micaceous schists. It is flanked on its east side by meta- 

 morphic Cretaceous limestone, which also forms the northern outrunner of this 

 spur. Want of water and grass rendered it an impossibility to make a closer 

 examination; nevertheless I have no doubt that the red and greenish schists 

 cropping through the limestone in the gulches of the Van Horn Mountains 

 are connected by this spur with the Carrizo Mountains. The elevation above 

 the surrounding flats of this mountain range (the Carrizo) is not as high as 

 that of the Quitman Mountains. It extends in a north (slightly east) direction 

 about twenty miles and is about six miles wide. The western limits of the 

 southern part of these mountains are near the 1 05th meridian at its crossing 

 with the Southern Pacific Railway, and its width to its eastern slope is a little 

 over six miles. This southern part of the Carrizo Mountains is built up of red- 

 dish, gray, and lighter and darker greenish crystalline schists, with numerous 

 intrusive quartz dykes, tilted and upheaved by this quartz and by granitic and 

 granitoid rocks, which on the north and northwest side protrude through the 

 schists. On the south side these schists disappear under limestones, and 

 these under the recent soil of the flats and gravel hills. These limestones, 

 denuded of the overlying strata, are fully exposed to view about two miles 

 west of Haskell Station in the ravines draining through Glenn's Creek the 

 east and north slope of the Eagle groups and the south slope of the Carrizo 

 Mountains. 



The crystalline schists cross the Texas and Pacific Railway near Allamore, 

 running into a low ridge, which six miles west of Van Horn Station disap- 

 pears in the flat at the foot of the Carboniferous cliffs, which rest on non- 

 fossiliferous red and brown sandstones and grit. The grit consists of rounded 



