APPENDIX D. GEOLOGY. 143 



of the Rio Puerco and the east base of the Sierra de Tunecha, or 

 through a longitudinal interval of 7f-°." (Report, p. 14*7.) 



8. Lieutenant Abert found strata, which he regarded " indubitable 

 proof of the existence of coal," in latitude 36^°, and longitude 104|- . 

 (Report, p. 21.) 



9. In 1818, Mr. Bringier described "a large body of blind coal 

 (anthracite) equal in quality to the Kilkenny coal, and by far the best 

 he had seen in the United States, immediately on the bank of the 

 Arkansas, a little above the Pine bayou, five hundred miles from its 

 mouth, in latitude 38°, and longitude 98°." (American Journal of 

 Science, vol. 3, p. 41.) 



10. On Monk's map of the United States, (1853,) I find two spots in 

 Texas marked as "beds of coal," one in latitude 29°, and longitude 100°; 

 the other in latitude 28f°, and longitude 101°. 



I might, perhaps, add, that Dr. F. Roemer describes a belt of granitic 

 and palaeozoic formations, the latter of carboniferous limestone and 

 silurian rocks, surrounded by a vast deposite of cretaceous rocks, be- 

 tween the Pedernales and San Saba rivers, in the northwest j^art of 

 Texas. The occurrence of such rocks, especially of the carboniferous 

 limestone, affords a strong presumption that the formation that usually 

 lies next above this rock exists in that region. 



If, now, leaving out the cases described by Fremont as most probably 

 brown or tertiary coal, we locate the others mentioned above upon a 

 map of the United States, we shall find a region lying between latitude 

 28f-° and 43°, and between longitude 94^° and 109°, containing not 

 less than nine deposites of coal, either bituminous or anthracite ; some 

 of them one or two hundred miles long. Its northern limit is the north 

 branch of the Platte river ; its eastern limit Fort Smith, on the Arkan- 

 sas ; its western limit in the country of the Navajoes, in New Mexico, 

 and even beyond the summit-level of the Rocky mountains ; and its 

 southwestern limit the Rio Grande, in the southwest part of Texas. 

 These limits would give a north and south diameter of one thousand 

 miles, and an east and west diameter of six hundred and eighty miles ; 

 an extent of surface three times larger than that of all the coal fields 

 in the United States hitherto described, which cover only two hundred 

 and eighteen thousand square miles. Yet, in view of all the facts, I 

 think the geologist will be led strongly to suspect that a large part of 

 this vast region at the southwest may be underlaid by coal. The 

 larger part may be, and undoubtedly is, covered by newer deposites, 

 especially the cretaceous and the tertiary ; and doubtless the older rocks 



