2 
Transactions Texas Academy of Science. 
[ 116 ] 
The topographic features of the Austin chalk are “much milder” than 
the Comanche Peak, and other Lower Cretaceous horizons. The rock is 
also much softer and less crystalline. The fossils are different and the 
fossil horizons are not so distinct. The Austin chalk, generally speak- 
ing, is of great uniformity throughout its extent, but there are pockets 
of clay or marl of considerable size scattered through it, and some places 
are found where the rock is very hard, as if it had been exposed to heat. 
The rock is seen in hard lumps of a yellow, pink, and black color, and 
some of these pieces are as hard to break with a hammer as some of the 
hardest volcanic rocks. The rock, around these hard places, being softer, 
weathers out, and the hard parts are left covering the surface. Such 
places are only of limited extent, and occur at intervals. On disinte- 
grating the limestone forms a black soil from 2 to 40 feet thick. Both, 
oil and asphalt have been found in the Austin chalk of this county, 
but it has not yet been demonstrated that they are in paying quantities. 
There are many faults in this formation, and in some localities the 
rocks are seen inclined in several directions. 
One of the characteristics of the Austin chalk is the presence of large 
veins of calcite. They usually occur running north and south along 
fault lines, and are from J to 4 inches wide, and can sometimes be traced, 
across the country for 3 or 4 miles. These calcite veins are also seen 
in the marl at the base of the Austin chalk, but they are not so large 
nor of such great extent. There are many nodules of iron pyrite scat- 
tered through the limestone, and in some places where they have weath- 
ered out they cover the surface of the ground. The chalk is also found 
in various, stages of disintegration. It breaks up into fragments and 
cracks and seams are seen running through it in every direction. 
Often the whole surface of a hill is covered with loose pieces, some • 
very finely divided. The frost seriously affects the .chalk, causing 
it to disintegrate very rapidly. The white limestone layers are, when 
first exposed, softer than the blue limestone layers, and are not so com- 
pact, but the white stands exposure much better than the blue, for the 
latter, on being exposed to atmospheric agencies, is soon reduced to 
powder. The white rock is soft and chalky, and turns yellow on weather- 
ing. The blue layers turn a lighter blue. Both are very compart, and 
will hold water when used for the walls of a cistern. The blue rock 
holds the water better than the white, and makes as good a cistern as 
if cement had been used. On account of its poor transmitting qualities, 
the surface wells dug in the Austin chalk do not afford as much water 
as those dug in the other Cretaceous formations. 
The thickness of the Austin chalk, as given by Prof. Robert T. Hill 
and Mr. Taff, is 500 feet. The best exposure in this county is found at 
Lover’s Leap, on the Bosque, north of Waco. Here it is found exposed, 
without the marl, in a bluff 150 feet high. This section is as follows : 
