Survey of the Concho Country. — Cummins-Lerch . 325 
and dips from northwest to southeast about 30 feet to the mile. 
It is easily recognized even from a distance, standing out in con- 
ical hills with flat tops and gently rounded ridges, sometimes 
with bold escarpments of an amphitheatre-like appearance. The 
surface of the wider plateaus lying between rivers and creeks, 
falls slightly toward the southeast, following the general dip 
of these strata. Their borders are broken b}' ravines, leaving 
the above mentioned hills and ridges. Frequent and contin- 
ued washings have covered the bases of the hills with detritus, 
making gentle declivities, covered with a spare vegetation of 
grasses and mesquite brush. Along the hillside the deposits 
are well exposed, facilitating the study of their dip, strike and 
composition. They vary from a few^ inches to many feet in 
thickness, with slight changes in the same horizon. The Cre- 
tacic has been conformably deposited in this country, but the 
different changes of level of this group are well defined by dif- 
ference of composition, density and color. The cleavage of the 
rocks is horizontal, along the strata, but frequentl}'- the rocks 
appear vertically cracked, the cause of which is pressure of 
over-lying rocks, moisture and frost. The material of this 
Cretacic group changes from hard blue limestone often semi- 
crystalline, passing through different stages of density and col- 
or, to pure, white, soft stone ; sometimes it is argillaceous, 
sometimes arenaceous, changing in color from a yellowish 
brown to a dirty brown or red. A peculiar brecciated lime- 
stone we have found interstratifying these layers near the top 
of this group. It is composed of hard limestone pebbles of a 
blue-grayish color, embedded in a calcareous brown yellowish 
matrix, which when exposed is easily washed out, leaving the 
ilmestone pebbles in their former condition. These exposed 
strata are then called by the people "honeycomb rock" from their 
peculiar appearance. Overlying this rock is a dense yellowish 
colored limestone, indicating the change from a shallow beach 
to the deep sea. According to the sections examined there is 
sand or loose sandstone at the foot of this Cretacic group 
which is so generally found in other countries constituting the 
lowest member of this period. No violent action has disturb- 
ed the almost horizontally deposited Cretacic strata in this 
country, but a gradual rise, the lifting force working vertically 
to the dip, has placed the deposits beyond reach of the waves 
and has sent the water to the gulf. The thickness of the whole 
