DESCRIPTIVE GEOLOGY. 687 



All I could learn was from a trapper (Mr. Stringfellow) who, with a com- 

 panion, had made a trip through this canyon on a boat brought from El Paso. 

 He describes the canyon as a narrow "split," mostly through a blackish rock. 

 This split, he tells, is frequently not more than six feet wide, with numerous 

 short turns around sharp corners. Through this channel the river rushes (in 

 some places at least one hundred feet deep) over rapids till it reaches a place 

 where it falls over a precipice into a basin with a small island of bowlders and 

 smaller debris. From these the river flows with tremendous velocity into a 

 broader channel. 



On a reconnoitering trip in 1889 I tried to approach this island from the 

 lower end of the canyon, but I found it impossible. Owing perhaps to a rise 

 in the river there were no banks, and I had to desist from forcing my way up 

 the stream, as no boat can be had in this unsettled country. Judging from the 

 statement of the trapper, the velocity of the flow is too great, the light is too 

 dim, and there being no places to effect a landing, it would seem impossible 

 to make satisfactory observations from a boat floating down the river. If at- 

 tempted at all, an exploration trip down the canyon ought to be made during 

 a high rise in the river, when the rocks in the rapids are sufficiently covered 

 with water. This description of the canyon, as well as the remarkable fact 

 that the river here cuts obliquely through high mountain chains, confirms the 

 supposition that this channel, draining the Cretaceous basins of Trans-Pecos 

 Texas, part of Mexico and New Mexico, was opened by very forcible volcanic 

 action, which extended far west and north and elevated these countries with- 

 out the subsequent subsidence following in Eastern Texas. 



The Rio Grande changes at right angle its southeast course at the canyon 

 to northeast and follows this course, cutting crossways through the mountain 

 ranges. Turned once in this direction it was quite natural that the water, 

 after having passed through the high St. Jago (Sierra Contrario) range on 

 the Texas side and its continuation in Mexico, cut its way through the softer 

 material of the lower country east of the St. Jago Mountains, probably fol- 

 lowing already existing drainage channels to the bed of the Pecos, from where, 

 joining this river, it resumed again the southeast course. 



To confirm this supposition it will be necessary to make careful examina- 

 tions of the Chisos and Corazones mountains, the lower St. Jago range, the 

 mountains on the Mexican side of the river, also the country east of the 

 Sierra St. Jago and Sierra Carmen. The mountains of Foley and Buchel 

 counties, such as the St. Jago, Chisos, Corazones, Rosillas mountains, the 

 Mount Ord range, are hardly well enough known to demonstrate even their 

 existence as separate ranges. The metamorphism is so complete, the eruptive 

 dykes so frequent, and protrusions so detached, that at present it is impossible 



