360. A Sketch of the Geology of Texas. 
lar oak trees of earlier growth in the same region. But this is 
evidently a mistake, as the fragments bear distinct marks of hay- 
ing been rolled and transported by water ; and the question arises 
as to. the geological formation 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 color 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 origin from creta- 
ceous strata. But it is an objection to this view, that no re- 
mains of dicotyledonous plants (the Conifere and Cycadex ex- 
cluded) have hitherto been found in strata older than the tertiary 
deposits, excepting the leaves of Credneria in the green sand of 
Germany ; and moreover, the fossil wood becomes scarce as you 
approach the hilly country where the cretaceous strata are im 
place. We may hope that the doubt will be removed by an ex- 
amination 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 T'rmity and Nueces rivers, tte num- 
bers of petrified trees lie imbedded in the soil. 
» The thickness of the diluvial beds diminishes ae you pa 
proach 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 sur- 
face until you pass that line. At the same time the topographical 
character of the country entirely changes. Instead of the low 
undulations of the prairies, hills of considerable height. with 
sharply defined outline, and but -a. short. distance beyond, : 
mountain ranges show themselves to the north, marking the limit 
between the rolling and mountainous region of Texas. | ~ 
The place where [ first met with a cretaceous deposit: samara 
New Braunfels, exactly where the old Precidio road from Sam 
Antonio to Nacogdoches crosses the Guadaloupe. Here in the 
bed of the river a white limestone is exposed which looks very 
Similar to the “chalk marl” of England, and to the “ planer- 
kalk” of Saxony. It is white, rather compact, in some beds 
more marly, and occasionally it contains green particles of silicate 
of iron. The stratification: is perfectly horizontal. ‘Some of the 
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