140 Sioux City Academy of Science and Letters. 
narrow, V-shaped ravines that sometinies terminate in 
abrupt escarpments which rapidly recede up the valleys. 
The rapidity with which such an earth water-fall 
escarpment recedes, with the formation of potholes of 
great depth, is often a serious menace to farmers who 
not only lose considerable land in this way, but are 
obliged to rebuild fences and roads which are thus de- 
stroyed. In Sioux City, this feature presents a serious 
problem in engineering, viz, the preservation of paving, 
sidewalks, railway tracks, and underground pipes from 
the encroachment of “washout” gullies. 
Such ravines as these where cut back into the escarp- 
ment from the river floodplain are usually short, steep, 
heavily wooded, and with sides almost too steep for 
climbing. 
At the edge of the great escarpment the lateral 
drainage has at many places nearly cut off and isolated 
points or hills, which stand as outliers, connected to the 
upland by low ridges and saddles. i 
These buttresses have been developed on the heavily 
bedded sandstone, which, in the southeastern part of the. 
county and again a little north of the middle, rises high 
above the flood plain. Above the massive sandstone the 
clay weathers more easily, giving more gradual slopes 
except where protected by an overhanging cap of lime- 
stone. In such eases the high cliffs are formed that occur 
near the Dixon County line, and along Big Sioux River 
north of Sioux City. Toward the south end of the county 
these limestone beds once rose much higher than at pres- 
ent, and erosion has removed them to such an extent that 
they no longer project over the clays and a more rounded 
brow has been developed along the escarpment. The 
sandstone beds, however, rising high and being separated 
from the limestone by a less thickness of clays, maintain 
the steepness of the lower face of the ESOT ENE south- 
east of Homer. 
From almost any point along the top of the escarp- 
ment in Dakota County a survey of the dissected upland 
reveals a striking and picturesque succession of views— 
the hills, ridges, and peaks standing out sharply, with 
beautifully flowing lines and concave slopes, “well illus- 
trating the remarkable characteristics of the loess to 
retain the delicate tracery impressed upon it,” as Bain 
