XXX11 REPORT OF THE STATE GEOLOGIST. 



along the coast, and as we pass towards the interior we find the ex- 

 posed areas of the outcroppings of the older strata of these formations 

 succeeding each other in regular descending order. 



All strata southeast of the oldest rocks of Llano County have a 

 general dip southeast, while those northwest, excepting the strata of 

 the Cretaceous, usually dip northwest. 



QUATERNARY. 

 COAST CLAYS. 



Immediately bordering the Gulf shore, and forming the underlying 

 slope, on which its waves roll their sands and help to build the bars 

 and islands that fringe the mainland of our State, and further inland 

 rising into bluffs against whose feet the gently moving waters of its 

 bays beat ceaselessly, we find a series of beds of clays, and sandy clays, 

 blue, yellow, red, and often mottled, which frequently appear black 

 upon the surface, from the combination of vegetable matter with the 

 lime of the calcareous nodules which are found scattered through them. 

 These clays are heavy, massive, containing small crystals of gypsum 

 in places, and are so compact that bluffs of from fifteen to twenty feet 

 in height are often found along the streams and bay shores, even in 

 such a moist climate as that of Eastern Texas. 



The various strata which form these beds dip so slightly to the 

 southeast as to appear nearly horizontal, and form the basis of the level 

 coast prairies, which stretch inland from the Gulf for distances varying 

 from 50 to 100 miles, their broad expanses broken only by the timber 

 fringing the streams which cross them, and the islands or motts of 

 live oak, pin oak, and sweet gum scattered here and there. This 

 gentle dip prevents their natural drainage to some extent, and for this 

 reason they have not yet reached that state of agricultural development 

 which the exceeding richness of their soil most certainly warrants. 



The prairies rise gradually and gently from the Gulf, and the only 

 elevations (except Damon's Mound, Brazoria county,) are small mounds 

 of from ten to twenty feet in diameter, and not more than two or three 

 feet in height, which are composed of soil differing in some degree 

 from that immediately surrounding them, and covered by entirely dif- 

 ferent vegetation from that of the adjacent prairie. 



Throughout the region where these clays prevail the dry weather of 

 the summer causes them to crack open in extended seams of consider- 

 able depth, which are closed again by the swelling of the clay directly 



