26 Contributions to the Geology of Texas. 
very favorable opportunity to visit'that section of country which 
lies between the Piedernales, Llano, and San Saba, (all three of 
them tributaries of the Colorado,) and which, on account of the 
dangerous character of the Indians -by whom it is inhabited, has 
remained until now, almost entirely unknown. - In this region, I 
found besides’ the cretaceous’ formation, not only an extensive 
tract of granite, and other crystalline rocks, but also stratified de- 
posits, which from the fossils they contain, ate clearly Silurian 
strata, and carboniferous limestone. In order to make the geo- 
graphical distribution of these rocks distinctly understood, it will 
necessary fir: st; to point out the route which I took in the tno 
ploration of ‘this. oy “Starting from Fredericksburg, a Ger 
man settlement 1 is situated about n ninety miles ‘north of 
the Piedernales, we took a northwestern course, and followed it 
not only as far ‘as the Llano river, but also beyond it, until “we 
reached the San Saba. We then ascended the valley ‘of this 
river about fifty miles, until we reached the San Saba, that is to 
say, beyond the ruins of the old Spanish fort, and within about 
eight miles of the sources of the river. From ‘ther ere, We went 
down the valley again, passed the point where we first struck it, 
and continued Tocencithe the valley, until we arrived at a camp 
of the Camanche Indians, about twenty-five miles from th 
mouth of the river. There we left ‘the valley of the San Gabe, 
and went back to ar ee in an almost neong southern 
course. On this tour'the following rocks were observ 
From the Piedernales to the Dine, the same cxiscionetit strata 
extend, which, consisting’ of @ compact white, or yellowish lime- 
stone, with occasional nodules of flint, oecupy likewise the wh 
tract of land from the Piedernales down to San Antonio and Austin. 
On the banks of the Llano; a calcareotis sandstone distinctly stra- 
tified, but evidently much altered, begins to show itself; its ex- 
tension, etn ash is jos a limited cae for about five miles be- 
re 
~ San Saba, and’ it is only on the dividing rn of the last menh- 
tioned river, that limestone beds pe geese 
The granite is on the whole, co a wma 
from the color-of the feldspar. It consis ee large 
with bold outlivies, or flattened masses, which -peojeet only 
little above the surface of the ground, an re ha 
in the beds of ‘several ‘small streams, by which ‘the country is in- 
terse 
cted. 
pon ten miles from the place where we first entered. the San 
Saba valley, on the right bank of the river, horizontal beds of 
limestone, of a decidedly Paleozoic character, were first met with. 
This limestone, of a grayish impure color and of a grenhuben age: 
