1674, 675, 676] southern river counties. 315 



THE SOUTHERN RIVER COUNTIES. 



Comprising the Counties of Wilkinson, Adams, Franklin, Jefferson, 

 Claiborne, Warren, and parts of adjoining Counties. 



674. A. Surface Conformation. — The hilly region which borders 

 the Mississippi River, from the Louisiana line up to Vicksburg, and 

 thence extends upwards for some distance between Big- Black and 

 Yazoo Rivers, and known in part, as " The Cane Hills ", is strongly 

 characterized by the peculiarity of its surface conformation, no 

 less than by that of its soil, and of the formation which, with few 

 exceptions, immediately underlies the loam stratum which usually 

 forms the subsoil of the uplands. 



But a small part of the territory above alluded to, has been specially examined 

 as yet ; a general examination, however, has shown a considerable degree of 

 uniformity to exist between (in the uplands at least) its several portions, so that 

 specimens of the several strata which concern the agriculturist, severally taken 

 in Wilkinson, Adams, Jefferson, Claiborne and Warren counties, are so nearly 

 alike in appearance, that differences can only be perceived when the several 

 specimens are placed side by side. 



675. The leading characteristics of the surface conformation of 

 this region, are produced by the deposits of calcareous silt* or 

 loam, of an age comparatively recent, now generally known to 

 American geologists, by the name of Bluff formation (1327). The 

 material of which this formation is here composed, and which but 

 rarely shows any indications of stratification, has a tendency, when 

 exposed to the action of water, to form steep and abrupt hollows ; 

 and where it forms the surface material of the ridges, these are 

 usually very sharp on their backs. Most generally, however, the 

 grey or bluff calcareous silt is overlaid by a stratum 3 to 10 feet 

 in thickness, of solid brown, clayey loam (1332), which in most 

 cases forms the subsoil of the region, and from which, of course, 

 the surface soil also is usually derived. Wherever this loam, 

 which washes readily, forms the surface of the ridges, we have level 

 plateaus, well adapted to agriculture in every respect, which break 

 off very suddenly into deep and narrow gullies, wherever the 

 washes formed sink so low as to penetrate to the calcareous silt 

 stratum beneath. 



676. The average thicknees of the calcareous silt stratum over the whole 

 region, I should estimate at between 25 and 35 feet. It was evidently, however, 

 deposited on a surface already very uneven, formed in most cases by the strata 

 (of clays and soft sandstones) of the older tertiary ; hence we find it in some 

 places as much as 70 feet in thickness, while in others (as at Grand Gulf, and on 

 the backs of the ridges of the Walnut Hills, above Vicksburg) the underlying 

 rocks are covered by only a few feet of the material in question. For this reason 

 yery abrupt changes of its thickness sometimes occur; as in the City of Vicksburg, 

 where the silt is 50 to 60 feet in thickness S. of the creek ; while just N. of it, 

 at the well-known bluff, its thickness is but 10 to 20 feet (1[270, Sec. 31). 



*The term "silt" implies a fine, powdery deposit, or with too little clay to 

 deserve the name of loam. 



