SURFACE GEOLOGY. 25 
stantly present, but it is less conspicuous than farther north, because it 
is thinner, is more generally covered with later deposits, and has been 
cut away along the great channels of drainage, through which the waters 
of the lake-basin were drained into the Ohio. It isasomewhat singular 
circumstance that the bowlder clay is more continuous in the counties 
which lie along the margin of the Drift area, than nearer the divide 
where the Drift deposits are thicker; probably for the reason that shore 
waves and draining streams have been more general and powerful in 
their action, and have removed the clay in the region where it is less 
abundant. Throughout most of the southern counties of the State the 
bowlder clay may be found in many exposures, forming the basal portion 
and perhaps half the thickness of the upland drift. In the valleys it is 
less constantly present. In the reports of Prof. Orton, on Hamilton, 
Clermont, Highland, Montgomery, and other counties, more detailed 
descriptions of the Drift deposits of southern Ohio will be found than 
can be given here. A type section, however, from Clermont county, 
quoted from Prof. Orton’s report, will serve to give a good general idea 
of the relations of the bowlder clay to the other members of the Drift 
series. 
SECTION OF DRIFT, SOUTHERN OHIO. 
No. 1. Soil. 
No. 2. Surface clays, generally white ; sometimes blackened by swampy 
COMMIBIONSMENMLIrElysIrEe LOM ONAN Eleascesecctescaedess-cbecescuseeesass 1 to 8 feet. 
No. 3. Yellow clays, abounding with gravel, with occasional bowlders, 
often constituting the surface instead of No. 2; seldom over... 10 feet. 
No. 4. Forest soil; a stratum of carbonaceous clay, containing vegetable 
matter, with occasional beds of peat; in some districts re- 
LACE AMMO CMEOMIOT Er seeere acs core cocenentwonctWelcegiea ceeaceuns eeusb vate 1 to 8 feet. 
No. 5. Blue bowlder clay, or hard-pan, with occasional layers of sand 
MLenCal ate dame shine OM auMNe mOckay) MOOK weqcresje-cetssssecejec see se ioe 5 to 20 feet. 
_ Prof. Orton thus describes the bowlder clay of this region: ‘‘The 
bowlder clay, or hard-pan, is found very generally, but not universally, in 
the northern and central regions of Clermont county. It is shown in 
many of the natural sections that are furnished by the streams, and in 
such artificial sections as are carried to sufficient depth. It is covered by 
varying thicknesses of the remaining members of the series. Where 
the total depth of the Drift beds reaches twenty feet, a ful,half of the 
section generally belongs to the bowlder clay. It cannot be confounded 
with any other formation in the district in which it occurs. It is 
composed of dark-blue, fine-grained, and tenacious clay, holding pol- 
ished and striated pebbles and bowlders. Most of the pebbles are de- 
rived from the blue limestone formation, though frequent representatives 
