Age of the Cincinnati Anticlinal. — Foerste. 101 
the sandstones, whether containing quartz pebbles or only small 
quartz grains, could have been derived from Cincinnati anticlinal 
regions, since the size of the quartz fragments is simply a ques- 
tion as to the degree of comminution sustained. The earliest 
sandstones therefore, of Devonian age, arc proof positive of a 
source of material different from the Cincinnati anticlinal area. 
Some of the Devonian shales, however, contain minute fragments 
of quartz grains readily visible in sections under the microscope. 
The larger of these also could not have come from the anticlinal. 
It is only a question therefore of numerous slides from various 
shales intervening between later Devonian and Clinton times to 
determine the earliest date at which the shales of Cincinnati 
group age could no longer have; provided the materials for the 
shales of certain later strata. Very minute quartz grains may be 
present in Cincinnati group shales, and may have found their way 
into later formations. 
When the rapid succession of shales and limestones in the Cin- 
cinnati group is considered it seems impossible that the great mass 
of Devonian shales could have derived the necessary materials for 
their formation from anticlinal regions without a much more pro- 
nounced intermingling of limestone elements from that source. 
It is evident that an area which has become a seat of deposition 
ceases to be a source of supply to other formations. Thanks to 
natural gas excitement, and to Prof. Orton's skillful utilization of 
its results, we know that the anticlinal areas of Ohio now covered 
by strata of later than Clinton age show everywhere, at the 
.proper horizons, characteristic Clinton strata. Connecting out- 
liers of Clinton age in southwestern Ohio, with neighboring contin- 
uous sheets of that formation and with each other, the area of 
Cincinnati group rocks left exposed is considerably diminished. 
Imagining Clinton strata then; where the thickness of the nearest 
still exposed Clinton areas, and their known rate of increase or 
decrease in thickness, would lead their former necessary existence 
to be inferred, the area of Cincinnati rocks still left exposed in 
Ohio, would be a comparatively small region in the vicinit\ ..l 
Cincinnati. Where a geologist might reasonably infer the previ- 
ous existence of Clinton strata is likely to be determined largely 
by previous prejudices. There is no reason for denying their 
former existence, even over that area near Cincinnati, where their 
