326 
The soil surveyors cover each section by “forties” and their map agrees 
very closely with the topography (see Plate LXXIII). Near Alto Pass, 
when timber maps and soil maps were compared it was found that the 
present timber areas corresponded very closely with the yellow silt loam 
tvpe of soil, the ridge tops and bottoms having been largely cleared. 
The gray silt loams are also found on the ridge tops, while the 
yellow silt loams are below, coming to the surface on the slopes. As the 
topography near the bluffs on the western side is a series of narrow val- 
leys separated by long, exceedingly narrow-topped ridges, the prevailing 
soil type is the yellow silt loam. At distances varying from four to five 
miles from the western bluff, the ridge tops become wider and the yellow- 
gray silt loam occurs with increasing frequency. 
These two soil types are both characterized by porous, friable surface 
soils and pervious subsoils. They are capable of absorbing large quan- 
tities of water and are very resistant to drought. They do not bake hard 
when dry, but remain loose and porous. 
While rated high as agricultural soils, both types are deficient in 
nitrogen, although the yellow silt loams of this area seem richer in nitrogen 
than the average upland-timber yellow silt loams. 
The body of continuous timber follows closely the yellow silt loam. 
area, not because of any relation between timber types and the physical 
or chemical nature of the soil, but because these soils are found over the 
very rough topography. Both the yellow and the yellow-gray silt loams 
are suitable for agriculture, but the yellow silt loam is found on the steep 
slopes which tend to erode if cultivated and hence have been left in 
timber. As a test of this statement, we have found that if the soil map 
of the Alto Pass region of Union county showing the yellow silt loam 
were superimposed over the timber map made by our party, the two would 
closely coincide so far as the upland area is concerned. 
The soils derived from chert are apt to have a poor moisture-retaining 
capacity where the rock fragments are fairly large. This kind of soil 
resembles gravel, but the fragments are angular and flinty. The degree 
of chertiness is reflected in the type of tree growth, in the extremely 
cherty soils, the general forest of white oak, black oak, and hickory giving 
way on them to a very inferior post-oak type. The shortleaf pine on the 
western slopes of the bluffs near Wolf Lake is on a moderately cherty soil. 
B. Bottomland soils—As the eroding process is general in the 
uplands, the flood-plains of the secondary streams draining these: uplands 
are constantly receiving a portion of the wash from the slopes, strips of 
sedimentary deposits being thus formed. With the exception of the val- 
leys of the Big Muddy and Cache rivers, these strips are very narrow. In 
general such soils are mixed loams (see Plate LXXII), and since they 
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