102 



eastern parts of the county is not more than ten or twelve feet to the 

 mile, but it increases to fifteen feet or more in the western part of the 

 county. 



The streams flowing into tlie Ohio directly have had to erode their 

 valleys through the very resistant upper Hudson, Clinton and Niagara lime- 

 stones. Consenueutly their courses are short and gradients very steep. 

 The Wabash-Ohio divide in this part of Jefferson county is in places but 

 one or two miles from the Ohio river, and at a comparatively short dis- 

 tance from the outcropping edges of the resistant limestone formations 

 mentioned above. 



Big creek and tributaries have not yet succeeded in lowering their 

 beds to these resistant rocks, except in a very few places. Their erosive 

 work has been in the softer corniferous limestones and New Albany black 

 shale of the Devonian formations. The stream beds, in general, follow the 

 dij) of the rocks. In places the bed of the stream is upon the same layer 

 of rock for hmg distances. Excellent examples of this may be found 

 in the bed of Harberfs creek, between A'olga and i^myrna church, as well 

 as along parts of Middle B'ork and Big creek. The dip of the rock strata 

 has had nmch to do with the long, gently sloping streams flowing west- 

 ward. 



The tributaries that flow in an easterly direction and against the dip 

 are very short and their gradients very high. In many of them the water 

 pours into the main valleys over falls located but a few hundred feet from 

 the main stream. In one case an underground stream pours forth from the 

 face of a cliff into the principal stream. 1 he easterly flowing tributaries 

 eroding their beds largely or entirely in the black shale have cut some- 

 what longer courses than those in the limestone, but in no case do they 

 even approximate the length of the westward flowing tributaries. 



The meanders of these streams are in all ]irobability a consequence 

 of the variable resistance of the rocks folhnved by maximum erosion on 

 the convex side of streams. They are probably consequent on the slope 

 of the original land surface, although they may have been somewhat 

 modified by the thin mantle left by the glaciers. 



