Surface Geology of Burlington. 1053 
_ plain occupying the greater portion of the county. Near the sum- 
mit of “South Hill” section III. is exposed in a recently opened 
quarry :— 
SECTION III. 
1, Brownish clay, free from pebbles, becoming silty below, and 
gradating insensibly into No. 2.......0000sccccs eerstes sue IE 5 feet. 
2. Compactashen loess containing lésskindchen............. 9 feet. 
3. Red tenacious clay, upper portion containing much gravel, the 
pebbles small, rounded, mainly erratic, a few local flint and lime- 
stone fragments disseminated throughout..............62.000+6 1 foot. 
4. Large angular fragments of limestone and flint, the interstices 
ered With Ted aiai eaa a Gaia cts fae 2 feet. 
5. Upper Burlington limestone, exposed 20 feet. 
One quarter of a mile to the southeast, on the corner of south 
Fourth and Maple streets, a similar arrangement is shown, super- 
imposing the lower Burlington limestone. The quaternary bedi of 
the two places are manifestly continuous, but the elevation of the 
latter section is somewhat less than the former, and the deposits are 
all intensified; No. 1 of section III. having a thickness of six feet, 
No. 2 of 13 feet, and Nos. 3 and 4 together, of 6 feet. Southwest- 
ward from this exposure, perhaps one-fourth of a mile, a road cutting 
exhibits :— 
1. Brownish-clay silty or loess-like below....... n.00.. n0004. 10 feet. 
A Typical Tower W O E a 25 feet. 
3. Lower Burlington limestone, exposed 5 feet. 
Summarizing the observations herein briefly recorded, it is to be 
noted: (1) That the loess at Burlington, as in other portions of 
Towa, occurs only over the elevated areas, and the fossils contai | 
are all depauperate, evidencing, as pointed out by McGee and Call,' 
a much lower temperature of the air than at the present time, for it : 
is also urged by those writers that the deposits of loess took place 
in ice-bound basins ; (2) that the loess over the region under con- 
sideration has been hp atmospheric agencies more or less modified 
superficially, often to a depth of five or six feet—the upper portion 
losing ‘entirely its original character, but downward passing by 
insensible gradations into typical loess. This modification of the 
1 Am. Jour. Sci., Vol. XXIV., Sept., 1882. 
