E. W. Hilgard—Geological Reconnoissance of Lowisiana. 845 
trating the stratum of loosely piled, disjointed, rounded lumps 
of blue limestone, which kept tumbling in from the sides. This 
is evidently the oil-bearing stratum, and (reports to the con- 
trary notwithstanding) I am satisfied that no fresh supply of 
oil was found after reaching the underlying white limestone. 
The rare shells contained in the blue rock are too ill-pre- 
served to allow of specific determinations ; but their very state 
of preservation, no less than the peculiar lithological character 
of the rock, suggests at once the correspondence to the base of 
the Sabine Town bluff ; which is, moreover, corroborated by the 
comparative chemical and microscopic analysis. The lignitic 
nature of the intervening beds, as well as the occurrence of 
asphalt in the Vicksburg limestone of Mississippi, are sugges- 
-tive with reference to the oil-bearing feature. The overlying 
clay stratum likewise coincides. 
As to the underlying white limestone, it is a material utterly 
foreign to any of the Tertiary groups of the Southwest, while 
coinciding precisely with some of the limestone of the saliferous 
Cretaceous outliers of North Louisiana ; here again, chemical 
as well as microscopic characters coincide as strikingly as they 
differ from those of the blue oil-bearing rock. : 
For the immense sulphur bed underlying, we have no direct 
precedent, unless it be the occurrence of a sulphur-bearing earth 
in the gypsum formation on Delaware creek, on the southern 
border of the Llano Estacado, observed by Capt. Pope.* But 
the interstratification of sulphur and gypsum in the lower bed 
proves the closeness of their mutual relation, while the enormous 
thickness of the underlying gypsum bed recalls at once the 
e gypsum formation of the upper Red river, and the Llano 
tacado ; faintly represented by the gypsum beds of North 
Louisiana, and Arkansas. : , 
The age of the great gypsum formation has been the subject 
of much discussion. It ta always seemed to me that the great 
ying sum are known 
that hee belonged substantially to the same epoch. What- 
* Report of an exploration of a route for the Pacific railroad, near 32d parallel: 
p- 38. 
Geology, by W. P. Blake, 
