213 Geology of the Trinity Country, Texas. 



The arable soil in this region consists of a basis of marine sand, 

 mixed superficially with vegetable mould, but destitute of lime 

 or saline matter. The application of this marl could not fail of 

 greatly increasing its productiveness; and as the marl appears 

 to be pretty generally distributed over the country, it will no doubt 

 hereafter prove a cheap and efficient means of ameliorating the soil. 



In traveUing north from Houston, immediately after crossing 

 Spring Creek, thirty miles distant, we come into a region gently 

 rolling. Here we meet with small, rounded diluvial pebbles 

 interspersed in the soil, some of jasper, others of quartz, flint, 

 hornblende, &c. In my excursion, which extended as far north 

 as the Mustang prairie, eighteen miles above Robbin's ferry, on 

 the Trinity, these pebbles constantly presented themselves in the 

 hills, but I saw none of greater size than a pigeon's egg. They 

 are perhaps indicative of the nature of the rocks in the monntain- 

 ous districts lying to the northwest, having been transported 

 and worn by ancient marine currents. The eminences of the 

 rolling region rise from one hundred to three hundred feet above 

 the valleys. It is evidently of more ancient formation than the 

 level region just described ; nevertheless its outhne or contour is 



most 



narrow gorges usually from ten to thirty feet deep, occupied by 

 the present fresh water streams. Many of the high rolling prai- 

 ries have their surfaces, especially their southern declivities, curi- 

 ously marked with ridges and furrows five or six feet broad, as 

 though they had been rudely tilled by some former race of giant 

 plowmen. They have received the euphonical appellation of hog- 

 wallow prairies. Those who have observed the small, regular 

 ripple marks, impressed by the waves on the sands of a shallow 

 bay, or seen fluted and indented sandstone strata, high, dry, hard 

 and a thousand miles inland perhaps, — the petrified ripple marks 

 of an ancient sea, will have a correct idea in miniature of the 

 appearance in question. . May not these ridges and depressions in 

 the sandy soil be the remains of successive ridges thrown up by 

 the waves of a former sea ? If not, whence came they ? 



Still more ancient than the beds of diluvial sand and pebbles, 

 a formation of sandstone here and there presents itself at the sur- 

 face, yet obviously underlying the whole of the rolling country. 

 In some situations it has the hardness and all the other good quali- 

 ties of a freestone, most valuable for building purposes. In other 



