242 CENTRAL MINERAL REGION OF TEXAS. 



gether with his "Texas,"* has reared an enduring monument to this most 

 intrepid explorer and intelligent interpreter of nature. Considering the date 

 of his trip and the hostile character of the Indians, the quality of his work is 

 little less than marvelous. In these two masterpieces he practically demon- 

 strates the general geology of the region, and, with few errors, presents a 

 geological map which has been accurate enough for most purposes heretofore. 

 This author allows too large an area for the granite exposures, which he did 

 not and could not attempt to differentiate from the other crystalline rocks, 

 and he errs in placing an insulated patch of Paleozoic rocks (occupying the 

 general position of the Mason Mountain) within the granitic area. This ridge 

 was crossed by him, and it seems a little strange that he did not detect the 

 Cretaceous character of the greater portion of it.f But although Dr. Rceiner's 

 views must be modified in some instances by later discoveries, his map was 

 never intended as more than a preliminary outline, and it is noteworthy that 

 his statements of fact, and the conclusions drawn by him from his own ob- 

 servations merely, are mainly correct. He is entitled to the credit of first 

 announcing the certain existence of Lower Silurian and Carboniferous rocks 

 in this region, and of first reporting and describing characteristic fossils from 

 these horizons. J 



The United States and Mexican Boundary Survey, under charge of Major 

 Emory, covered some territory adjacent to and southward from the Central 

 region in 1853-4. The report of one of the geologists, Arthur Schott, as- 

 sistant to Dr. C. C. Parry, contains a generalization upon this tract, among 

 others not seen by him. The quotation is given here merely to explain that 

 recent investigations have shown it to be contrary to the facts. § 



Mr. Schott refers in detail to Roemer's observations, and then remarks: 



The geographical distribution of the rocks of which Dr. Roemer speaks permits only the 

 conclusion that all the marks of plutonic or volcanic formation must belong to the same 

 system, which, traversing the upper limit of the more recent Cretaceous strata in the valley 

 of the Rio Bravo, shows itself in the shape of the low basaltic hills, etc. * * * 



There is no doubt that this dyke continues its northeastern direction, accompanying as an 

 outlayer of the higher regions of the G-uadalupe and Ozark mountains, and thus probably 

 crosses the whole of Texas, and possibly Arkansas. 



This peculiarly broad generalization may, perhaps, be regarded as the first 



*Texas, etc., 1849; vol. xiv., 8vo., pp. 464, map. 



fThis fact was discovered only in the summer of 1889 by the present writer, and it is here 

 first announced in print. 



JTexas, etc., pp. 388, 389; 1849. Kreidebildungen, p. 1 ; 1852. Roemer had also an- 

 nounced this discovery in less detail in 1846. in his paper, already quoted, in the American 

 Journal of Science, vol. II, 1846, p. 364. 



§Report of United States and Mexican Boundary Survey. By Wm. H. Emory, Major First 

 Cavalry and U. S. Commissioner. "Washington, 1857. Vol. I, part 2 (G-eology), p. 34. 



