344 PROCEEDINGS OF THE ACADEMY OF [1893. 



small size, for the water stands in pools of varying size and trickles 

 from one to another in a tiny stream. These pools are enclosed 

 sometimes by bars and deltas, sometimes by walls of solid rock, the 

 pools themselves being the result of corrosion. 



The elevated plateau region west of this and east of the Pecos 

 River contains a number of lake basins of sink-hole type, but no 

 water, or at best very little, stands in them. Very probably there 

 are sink-hole basins on the Cretaceous limestone in east central 

 Texas. Still farther west, in the Trans-Pecos region, there are 

 several large lake basins, abandoned either in part or entirely, by 

 dedication. Here lakes of consequent origin, the result of mountain 

 deformation, have existed and will exist again if the conditions of 

 rainfall become favorable. 



Hence it is that Texas contains no large lakes : first, because there 

 are no regions of striking structural features, except one (the older 

 Palaeozoic area) in which erosion has long been in progress, and its 

 lakes long since destroyed, and one in a region too dry for the 

 existence of lakes ; and secondly, because erosion has tapped the 

 shallow lakes that formerly, no doubt, existed on the new Cretaceous 

 and Tertiary land. Sink holes in limestone regions frequently con- 

 taining small and shallow bodies of water, lagoons on the sea shore, 

 and oxbow lakes in the flood plains, constitute the major part of the 

 Texas lakes. To these might be added the expanded springs, the 

 laked streams caused by the overburdened condition of the main 

 stream (Pecan Bayou and San Saba River tributary to the Colo- 

 rado), and the chain of pools of the sub-humid region, formed by 

 the dessication of the river. The salt lakes, playas and alkaline 

 marshes and flats of the Trans-Pecos region are the dessicated rem- 

 nants of lakes, formerly of greater size, just as the pools are the 

 result of the annual dessication of normally continuous streams. 



9. — Summary. 



The State of Texas is a series of prairies, plains and plateaus, low 

 coastal plains in the east, elevated plateaus in the center, and in the 

 extreme west a plateau broken by mountain ranges. A buried 

 laud, now uncovered, forms a central hilly district. In climate the 

 State varies from the moist Gulf coast to the truly arid Trans-Pecos 

 region. 



The evolution of the Texas region began, so far as our present 

 records can show, with an old Palaeozoic or Pre Palaeozoic mount- 

 ainous land which was denuded at the beginning of Carboniferous 



