198 J. Hail on Carboniferous Limestones of Mississippi Valley. 
color below.* The laminations of this clay, in the upper part, 
conform to the curvatures and irregularities of the roof of the 
ancient cavern, and exhibit every appearance of having flowed in 
while in a semi-fluid condition; while the hydrostatic pressure 
of the mass above, operating through the deep funnel, had forced 
the soft mass against the roof, causing it to assume in its lamina- 
eds of limestone appears a black band 
extending for thirty or forty feet; beneath this, and of less hort 
zontal extent, is a thicker layer of clay, precisely like that of 
the cavities before described, and of the character of underclay ; 
still below this, and occupying the depth of the cavity is a coarse 
sandstone. This sandstone follows in its lines of lamination oF 
bedding the curvatures of the limestone upon’ which it lies, 
gradually filling up the cavity, and extending its laminse above. 
. 
at a depth of more than 5000 feet below the coal measures. 
_in instance the explanation is clear enough. It is only 4 
little more perfect in its members than the preceding case, and 
ane The reddish brown color is simply due to infiltration from the ferruginous drift 
, 
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