106 CRETACEOUS ROCKS OF TEXAS. 



To these strata the State owes a large part of her agricultural and general 

 prosperity, for they are the foundation of the rich black waxy and other 

 calcareous soils of those regions. 



In addition to their agricultural features they are the most productive 

 source of building material, while adjacent to the parting between them, ex- 

 tending the entire length of the State and dependent upon their stratigraphy, 

 is a remarkable area of natural and artesian wells, as seen at Fort Worth, 

 Austin, Waco, Taylor, San Marcos, and elsewhere. 



That these formations are of great economic value to the State, is also 

 shown by the fact that they are the site of our principal inland cities, and the 

 rich agricultural soils which surround them. 



This is in general a chalky country, and uniquely Texan, so far as the 

 United States are concerned, constituting a distinct geographic region, in 

 every topographic, economic, and cultural aspect, and one which should not 

 be confused with other portions of our country. It covers an area of over 

 73,512 square miles, or over one-fourth (28.27 per cent) of the total area of 

 Texas, forming a broad belt of fertile territory across the heart of the State, 

 from the Ouachita Mountains of the Indian Territory and Arkansas to the 

 mountains of Northern Mexico, an area larger than the average American 

 State, and equal to the combined area of all the New England States. One- 

 third of this region lies north of the Colorado River, and the remainder to 

 the southwest. 



This region, with its many different prairies, each covered by its peculiar 

 vegetation, its sweeping plains and diverse valleys, its undulating slopes clad 

 with motts of live oak, its narrow strips of cross-timbers, its ragged buttes 

 and mesas, presents a landscape varied, yet possessing as a whole an individ- 

 uality peculiarly its own. All of these features, with their different tints and 

 tones of soil and vegetation, with their varied conditions for human habita- 

 tion, are but the surface aspects of the system of chalky rocks (chalky 

 sands, chalky clays, and chalky limestones) upon which it is founded, and to 

 which is primarily due every physical quality of the country. In fact it is 

 the great chalky region of the United States. 



The rocks originated as sediments of the Atlantic Ocean, laid down with 

 great uniformity during two of the long epochs of subsidence and emergence, 

 when the waters covered this region many hundred fathoms deep. These 

 ancient sediments are now more or less consolidated and elevated into a fer- 

 tile land, which is decomposing under atmospheric conditions into soils and 

 debris, and in its turn being slowly transported to the ocean, where it will 

 make other rock sheets. They now occur in regular sheets or strata, dip- 

 ping beneath each other toward the sea, while the projecting western edges, 

 each of which weathers into and imparts its individuality to its own peculiar 



