IN THE UPPEB EIO GKANDE EMBAYMENT IN TEXAS. 85 



glomerate of rounded limestone pebbles. Above this there are 

 several heavy ledges of a white laminated and hard calcareous 

 tufa, from ten to twenty feet thick. This tufa must underlie the 

 land for more than a mile to the south, for it is exposed in the 

 sides of the cut along the Southern Pacific railroad from a half to 

 one mile east of Spofford. It is a rather pure carbonate of lime 

 and with the Cretaceous clay that underlies, it could be used in 

 the manufacture of good Portland cement. A suitable site for a 

 mill could be found next the road and no carting would be needed. 

 Both the limestone and the c\a,j would be right at hand. This 

 same stony tufa was also seen in the south bank of a creek near 

 the north line of survey 27 in block 9, south of the Anacacho 

 mountains. 



ALLUVIUM AND SOIL. 



Excepting the land where the Cretaceous limestones form the 

 bed-rock, and in a few other places, as in the Anacacho mountains, 

 where the weathering rocks are resistant, all streams have wide 

 valleys with well developed flood plains. These are built up from 

 a loani}^ alluvium, which has developed deep and rich black soil. 

 In many places these valleys may be said to be in a measure sub- 

 irrigated, for as the surface is desiccated under the summer sun, 

 capillary moisture ascends from the more humid alluvium below. 

 The supply is sufficient for a luxuriant vegetation of mesquite, 

 pear, grass and various shrubbery. It seems to me that much, if 

 not all of these alluvial lands, will in time have a greater value 

 as cultivated land, than as pasture land. With a rainfall 

 averaging twenty inches a year and with thorough cultivation, 

 the soil ought to be very productive. The quality of the soil is 

 such that it might even in time warrant the construction of tanks, 

 or reservoirs, for purposes of irrigation. I believe that thetime will 

 come when this will be tried on someof these lands. It is clear that 

 all of the Company's lands east of Del Kio have been selected for 

 the excellence of the soil for pasture vegetation. The surveys every- 

 where follow those tracts where clays and marls form bedrock and 

 subsoil. This is most notably the case north and west of Fort 

 Clark, where the surveys follow the outcrop of the Del Eio clay, 

 from Del Eio to within a short distance of the Nueces river. 



One circumstance which increases the fertility of the soil south 

 of the belt of the Austin chalk is the presence in the Cretaceous 



Library Publications. 6. 



