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reaches their tops in section 17, township 1 south, 6 east. Here it turns: 
to the west and passes west of Borden and on across Blue River. 
A glance at the accompanying map will show that the continuous line 
of outcrop as here described makes a bend to the west and then to the 
northeast, causing the knobstone to form the principal rocks in the yal- 
leys, at least nine miles from the true eastern face of the knobs in town- 
ship 2, south. 
It is seen, also, that by no means all of the rocks of this immediate 
locality belong to the Knobstone, but that there are, included within the 
main line of outcrop, some large outlying limestone areas. These out- 
lying limestones are, of course, only the remnants of the beds that at one 
time covered the entire region. As the process of erosion continues these 
limestone areas will gradually disappear. It will be noticed that to the 
south of the area of exposed Knobstones (in township 1 south) just de- 
scribed, there is a smaller area where the limestone has been cut through,. 
but where it still completely encloses the exposed underlying sandstones. 
To the north, in the region of Borden, there is also a large area in which 
the overlying limestones have been almost completely removed, leaving 
but one small limestone area to the east of the main outcrop. These three 
areas illustrate very well three different stages in the process of the 
dissection and removal of the topmost strata of a plateau. 
In conclusion, attention should be called to the distribution of springs. 
Since the rocks composing the Knobstone group are of such a nature 
as to prevent the free circulation of water, springs are by no means com- 
mon in that formation. At the top of the formation, however, the line of 
parting between the limestones, which do permit the free circulation of 
water, and the underlying impervious sandstones, is a natural spring hori- 
zon. Along this line of parting springs are very common, and except at 
the extreme eastern edge of the Knobstone escarpment, where the lime- 
stone has been eroded to a very thin edge, they are to be found in almost 
every small side ravine. 
