MiscellaneotLS. 4Sltit 



on the Colorado, Gonzales and Seguin, is nearly devoid of any geo- 

 logical interest ; you see no solid rock in place through the whole di- 

 stance, excepting irregular layers of a coarse calcareous sandstone of 

 very modern origin, exposed on the steep banks of some of the rivers. 

 The surface is elsewhere a thick diluvium of loose materials consisting 

 either of a fertile vegetable mould, or of rounded pieces of hydrate of 

 iron, as over the barren section between San Felipe and Columbus, 

 or of sand and gravel, as near Gonzales and elsewhere. 



The gravel and sand are of some interest on account of the abun- 

 dance of fossil wood which they contain at many different places. I 

 saw numerous localities of it between San Felipe on the Brazos and 

 Gonzales, and in the valley of the Colorado between La Grange and 

 Austin. This petrified wood is often found in large pieces, and it is 

 said that occasionally whole trunks of trees are met with, which 

 however I have not myself seen. The fossilization of the wood is 

 generally imperfect, the silex into which it has been turned showing 

 most minutely the original structure. Most of the wood is dicoty- 

 ledonous ; but not having the leisure or the necessary books of refer- 

 ence, I have not made out the species. I have only observed that in 

 some of the wood the fibres are extremely close, and the whole struc- 

 ture very compact, exceeding any tree in the existing flora of Texas. 



As the gravel and sand in which most of this fossil wood occurs 

 is generally covered by post oak timber, which alone grows on a soil 

 of such sterility, it is a common belief among the farmers of the 

 country that the fossil wood was derived from similar oak-trees of 

 earlier growth in the same region. But this is evidently a mistake, 

 as the fragments bear distinct marks of having been rolled and trans- 

 ported by water ; and the question arises as to the geological forma- 

 tion in which this wood was originally deposited and petrified. The 

 gravel where it occurs consists chiefly of rounded pebbles of silex, 

 mostly of a reddish colour, and of a similar appearance to the silex of 

 the cretaceous formation in the upper country. This might lead to 

 the supposition, that the wood as well as the pebbles derive their ori- 

 gin from cretaceous strata. But it is an objection to this view, that 

 no remains of dicotyledonous plants (the Coniferse and Cycadeae ex- 

 cluded) have hitherto been found in strata older than the tertiary 

 deposits, excepting the leaves of Credneria in the greensand of Ger- 

 many ; and moreover, the fossil wood becomes scarce as you approach 

 the hilly country where the cretaceous strata are in place. We 

 may hope that the doubt will be removed by an examination of the 

 eastern section of the country, where the fossil wood is said to be 

 still more abundant, and where according to Kennedy*, between the 

 Trinity and Nueces rivers, great numbers of petrified trees lie im- 

 bedded in the soil. 



The thickness of the diluvial beds diminishes when you approach the 

 cretaceous deposits, and when you are near the above-mentioned line 

 the cretaceous strata begin to show themselves in the deep ravines and 

 gullies ; but they do not appear at the surface until you pass that line, 



* Texas, vol. i. p. 119. 



30* 



