386 The American Geologist. December, 1902. 
Worth is built on this formatio.1. Above ihe Fort Worth limestone 
are beds (10) known as the Denison beds, which are mostly composed 
of clays, with frequent hard layers of impure limestone. These have 
ferruginous colors, such as chocolate, brown, and red, instead of the 
whitish lines which mark the preceding formations. The Denison 
b«ds pass into the western border of the Eastern Cross Timbers, where 
they are succeeded by another sandy timber-covered formation (11), 
the Woodbine, consisting of loose brown sand somewhat resembling 
the Trinity sands lying at the base of the whole section, but differing 
in particulars which are elsewhere described. In the upper part of 
these sands thin layers of blackish bituminous clay begin to alternate 
with the sand. Gradually the sand decreases and the clay increases 
until the latter makes the entire formation (12), the Eagle Ford. 
With the initiation of these black clays prairie lands again appear. 
The clays finally pass upward into a great formation of chalky lime- 
stone (13), the Austin chalk. This formation, upon which the city 
of Dallas is located, is some 500 feet thick. The chalk in turn passes 
upward into marly clays of great thickness, consisting in their lower 
part of unctuous, laminated, light^blue and yellow clays (14) which 
are knov.'n in Texas as 'joint clays,' and which we shall call the Tay- 
lor marl. These clays underlie the main Black Prairie for a distance 
east of the longitude of Dallas. The whole of the Black Prairie east 
of the Austin chalk is composed of soft, unconsolidated beds, but those 
above the Taylor marl are characterized by sandy layers, alternating 
with the clays, and especially by minute specks of glaucoaite. The 
sands and clays of this character, which constitute the final formations 
of the Cretaceous, are found along the eastern margin of the Black 
Prairie and may be called the Navarro beds (15). The Navarro beds 
are 'blacker and more arenaceous than the Taylor marl. The small 
laminse of glauconitic sand in the Navarro beds give to them a green- 
ish-yellow color in places. There are also some thin indurated bands 
of glauconitic sandstone and chalk marl in their upper portion." 
After the detailed descriptions of all these Cretaceous formations, 
the following generalized observations of their physical or lithologic 
characters in relation to the stratigraphy and fossil faunas are stated: 
"The paleontologic zones persist in horizontal extent regardless 
of changes in lithologic nature of the matrix. 
"The beds vary in lithologic composition aloi:ig horizontal lines 
toward or away from original shore lines of deposition. 
"Similar lithologic character diagonally transgresses time horizons. 
. . . Thus it is that everywhere at the base of the Cretaceous system 
there is a continuous bed of sand, which, when considered as a form- 
ation, transgresses much of the range of Cretaceous time." 
The flowing wells of this region vary in depth from 100 to 3,330 
feet; and they also vary greatly in their water pressure, from those 
of feeble flow, as a gallon per minute, to spouters of seven hundred 
times as great supply. In 1897 the number of flowing wells report- 
ed in this great district was 458; and the reports showed 506 other wells 
