20 GEOLOGICAL RECONNOISSANCE 
The section of the quarternary beds at the Chalk Bluffs, as far as they 
can be seen, is as follows: 
Height 
above ; Thick- 
135. Hill on which the ferryman’s house stands-++++++++++ +++ 
Soil and sub-soil +++ ee eee eee tere ce ee ee ee ee ener eee eerene ; 
Chert and hornstone gravel.++-+++eesseeee eee eee e eens 25 
110. Lowest point to which the upper gravel bed could be traced. 
105. Top of the first bench below the main gravel bed------- “ee 
Pink and variegated sand; locally indurated into a soft 
crumbling sandstone 96 feet or more in thickness. --.----- 96 
30. White siliceous clay shale or marly earth, slightly indurated 
atthe upper parte +--+ setts eee ere eee Bb Bre us iapik: Sea a arena Ve a 
6. Fine white potter’s clay 5 to 6 feet. +++ + see cree cece cence 6 
0. Low water of the St. Francis river. 
The materials which compose the gravel bed which underlies the sub- 
soil, seem to have been derived from the destruction of beds of carbon- 
iferous date, lying to the north in the State of Missouri. At this locality, 
it appears to be from 25 to 30 feet in thickness. It occupies the highest 
position of the beds of quarternary date at this locality. 
No solid beds of rock have been observed in this north-east termination 
of Crowley’s ridge. In sinking wells at levels below the gravel bed, they 
pass through sand, then streaks of clay and shaly materials, below which 
the sand continues. In this lower bed of sand the water is usually struck, 
which must be retained there by the lower beds of clay of the preceding 
‘section. Sometimes, in low situations, they pass through beds of clay in 
‘digging for water. 
A few chert and hornstone pebbles were observed disseminated amongst 
the sand at 40 feet above the river, but the principal gravel deposit of 
this part of Crowley’s ridge is in high situations above the great mass of 
sand. 
The growth on the high ground is mostly black and white oak; in the 
bottoms, a mixed growth. Considerable groves of cypress timber flourish 
in the bottoms of St. Francisriver, a short distance above Chalk Bluffs. 
An erratic mass of hornstone, weighing upwards of 50 pounds, was 
‘observed on the slope of the river bluff, near the ferry; and near by are 
. chalybeate oozings from the bank, originating, probably, from some scaly 
oxide of iron, sparingly disseminated in the adjacent bank. 
The potter’s clay at the base of the Chalk Bluffs is nearly white, or of a 
‘eream color; variegated, however, here and there, with flesh tints. Its 
