LETTER OF TRANSMITTAL. 
Department of the Interior, 
United States Geological Survey, 
Washington, D. G, May H, 1899. 
Sir: I submit herewith for publication a manuscript by Mr. T. 
Wayland Vaughan, entitled Reconnaissance in the Rio Grande Coal 
Fields of Texas. This paper treats of two areas, both of which, in 
addition to the economic considerations, are of scientific interest, inas- 
much as they give interesting types of the geology of the localities 
studied. 
The first of the areas embraces that portion of the Lower Rio Grande 
region lying between Del Rio and Laredo, and treats of a section of the 
Cretaceous and Tertiary formations and of the relations of the one to 
the other. This section has been an object of interest for many years, 
and, as shown in the literature cited by Mr. Vaughan, has been visited 
by many geologists. As the region is a transition ground between the 
phases of these formations hitherto considered peculiar to the Rocky 
Mountain and the Atlantic Coastal plains, respectively, such a section 
must necessarily throw some light upon the relations of the for- 
mations, including the age position of those hitherto ascribed to the 
Laramie ^poch. Mr. Vaughan could hardly be expected to solve com- 
pletely all the problems of the region in the short period of time during 
which he was permitted to examine it, but his paper will be a valuable 
contribution to a progressive series of researches which have been 
made in that territory. 
The second paper treats of the San Carlos coal field in Trans-Pecos 
Texas. This paper, too, is of great scientific interest, inasmuch as it 
j jives a detailed section of the Cretaceous beds of the Vieja Mountains 
)f the Trans-Pecos region, and also throws light upon the occurrence 
>f interesting volcanic rocks. 
Mr. Vaughan has treated the economic features more briefly than 
le would have done if the determination of the stratigraphic position 
•f these coals had not been the principal object of these preliminary 
econnaissances. 
Very respectfully, Robt. T. Hill, 
Geologist. 
Hon. Charles D. Walcott, 
Director United States Geological Survey. 
