REPORT OF MR. W. VON STREERUWITZ. 



Austin, Texas, March 31, 1890. 

 Mr. E. T. Dumble, State Geologist : 



Dear Sir — The portion of the State to which my field work was confined 

 during the year 1889 is that extreme western .part, embraced between the 

 Pecos River and Rio Grande, known as Trans-Pecos Texas, and the time I was 

 in the field was devoted principally to preparatory work and determinations 

 which were positively essential to a correct understanding of its geology. 

 For successful geological determinations and investigations of this part of the 

 country, the study of the topography is absolutely required. Eruptive rock, 

 of different periods and character, intrude into and penetrate the sedimentary 

 strata, which are also of different ages, and for the most part stroogly meta- 

 morphosed. 



The mountain groups and ranges and the hills are separated from each 

 other by wide, gaps and extensive flats, filled in with more recent deposits, 

 which adds greatly to the complications of the geological work in this part of 

 the State. ^ 



Another source of complication arises from the great erosion of the older 

 mountains by the Cretaceous sea, as well as from later erosions and intrusions, 

 and the covering of these by more recent materials after the Cretaceous de- 

 posits were formed. 



The information which can be derived from former records is meagre and 

 merely fragmentary, for the most part consisting of short remarks or discus- 

 sions, made more or less general and based on casual or disconnected observ- 

 ations during rapid trips; and consequently, even if the observer were per- 

 fectly trustworthy and of undisputed capacity, his information can only be a 

 very limited assistance to more exhaustive geological work. 



Existing maps of the counties west of the Pecos River have been compiled 

 mostly from records of old surveys, some of which are of very doubtful 

 value. The mountain ranges, rising precipitately from the extensive flats, are 

 so rough and so steep that running and measuring straight lines across them 

 is almost or quite impossible. The starting point from which such lines are 

 said to be run (on the New Mexico-Texas line) are far distant, and to reach 

 them many obstacles of a serious nature have to be encountered. Adding to 

 this the changes of the needle bearings, the absence of corner monuments, 

 and numerous other difficulties of less importance, which must, however, be 

 met and overcome, it becomes evident that the existing maps and surveys 

 can not be made the base for the determination of mineral districts and other 

 geological work in Trans-Pecos Texas. 



