\ 
364 A Sketch of the Geology of Tecas. 
rated, and form together a single continuous succession of strata 
of nearly the same age; and with regard to the age we can at 
present only say that the beds belong to the upper division of the 
cretaceous formation. It is interesting to compare these creta- 
ceous deposits with the cretaceous strata of New Jersey, Virginia, 
etc. In the latter regions we find beds of a loose calcareous 
marl and of ferruginous sand, representing the upper division of 
the cretaceous formation. In their fossils and also their miner- 
alogical constitution they bear a striking analogy to some depos- 
- its of England and Germany. In Texas, we have a system of 
rocks which equally correspond to the upper division of the cre- 
taceous formation, but of a very different character and not con- 
sisting like those just mentioned. of loose unconnected materials, 
but partly at least a very compact siliceous limestone.. By their 
fossils as well as the composition of the rocks they are closely 
allied to the cretaceous formation as it is developed in the sit 
of Europe along the Mediterranean. 
A new and interesting analogy in the. outa constitution 
of the two continents has thus been ascertained, proving the gen- 
eral similarity of physical condition and of the laws of organi¢ 
life in both hemispheres during the period when the cretaceous 
strata were originally deposited. 
Still another observation of a peneiak character remains to be 
ous deposits. About 20 miles.north 
of Bredesichebanay- shin new & Gorin settlement on the Piedernales 
river, a rock more than one hundred feet high with nearly per 
pendicular sides stands out from the ground. ‘This rock which 
very probably is identical with that which has been laid down 
on the maps of Wilson and others as “the enchanted rock,” ¢on- 
sists of a rather coarse grained granite. I obtained specimens 
of the granite from some friends of mine who were on the spot, 
and ascertained also that beds of limestone extended to the very 
base of the rock. This fact in connexion with the other one 
that on the San Saba river, silver mines have been worked. for- 
merly by the Spaniards in a plutonic rock, seem to lead to the 
supposition that here on the tributaries of the Colorado we arrive 
at the boundary where the stratified rocks of the east side of 
the continent come in contact with the crystalline masses of the 
ponisvale mountains. If this supposition is correct, it follows that 
the cretaceous formation is the only one of the whole wtOee 
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