The C'nirinnail Rocks. — Perrt/. 331 
I have found equally good ripple nuirks in the shale at other 
horizons, but })erfect as these are they are scarcely more so 
than those found in the limestone strata at a dozen or more 
horizons exposed in the bed of this same creek. I know of no 
locality Avhere the evidence of former wave action can be 
studied, on so large a scale and to such good advantage, as in 
the bed of this creek when it is dry. In making such a study 
one also becomes familiar with many otherindications of shal- 
low water deposition, which if seen alone would not warrant 
this interpretation, but associated as they are, seem to permit 
of no other construction. These have been invaluable to me 
in my later work, but Avhile I can not regard them when alone 
as positive evidence, yet they are presumptive proof which 
amounts almost to certainty when two or more are found 
together. 
Prof. C. W. Hargitt, having been appointed to the chair of 
Geology and Biology at Miami University, becoming ac- 
quainted with the work I was engaged in, became quite inter- 
ested and visited with me man}' o the localities where expos- 
ures of especial interest were to be found. I had not yet 
found mud-cracks, but he had, and at my request sent for a 
photograph of the same. He also kindly wrote a description 
of the specimen which I quote in full. 
"A rock measuring 17x26 inches (approximately) was 
obtained from the LoAver Silurian of Dearborn county, Indi- 
ana, at about 600 feet above the base of the Cincinnati group, 
as estimated from the surveys of the 0. & M. R. R., and from 
measurements taken from the Lawrenceburgh gas-wells, thus 
making the horizon at which these evidences are very marked 
about the same as that of the raindrop imi:)ressions, etc. 
This slab (mud-cracks) is now in the museum of Moore's 
Hill College, Indiana, wdiere it can be seen at any time. By 
chemical tests it proved to be a good quality of limestone, as 
is much of that found in the same region." (Fig. 3 ) 
Referring to the italicized portions of the quotation from 
Prof. Orton, which express reasons why some of these phe- 
nomena are not what they seem to be — Prof. Orton says that 
"the limestone layers alone being thus shaped is sufficient to 
set aside the explanation," viz. : that the wave-like structure 
was due to wave action. We have found that the ripple or 
wave-marks are not confined to the limestone strata : we have 
found several horizons where thev occur in shale. 
