SURFACE GEOLOGY. 33 



our Drift deposits, the Forest Bed represents a great lapse of time. The 

 advance of a forest growth over the barren Drift area must have been 

 slow, and much time was certainly required to form the distinct sheet of 

 carbonaceous matter which we now find. The climate of the State, at 

 that period, must have been cold and damp, as the glaciers were still 

 near, and the drainage from them which filled the water basin was icy 

 cold. 



In the Forest Bed of the valley Drift we find quite a number of plants 

 of the species now growing in the same localities, and such as could not 

 have grown there had the climate been much colder than now, but the 

 deep valley would have been warmer than the uplands ; and, as has been 

 already stated, it is not certain that the old soils of the valleys and the 

 highlands are of the same age, though both belong to periods when the 

 physical condition of the country was quite different from the present. 

 Further investigations, following up the suggestions and conjectures now 

 made, will undoubtedly result in the perfect elucidation of this interest- 

 ing chapter on the complicated history of the "Drift. 



I should not omit to mention that a stratum of bog iron ore accom- 

 panies the old soils in both the valley and upland Drift beds. 



DEIFT OF THE TEEKACE EPOCH. 



The materials which overlie the Forest Bed, and which form the upper- 

 most members of the stratified Drift deposits, are clearly the product of 

 a wide-spread submergence of an immense area in the Western States 

 which had before been dry land. In a great number of instances in 

 southern Ohio, where the Forest Bed is present, the materials overlying 

 it have been penetrated in water wells, and their character has been 

 accurately determined. For the purpose of showing what these strata 

 are, I quote again, in part, the general section of the upland Drift of Cler- 

 mont county, as described by Prof. Orton (Vol. I, Part I, p. 440) : 



No. 1. Surface clays, generally white, sometimes blackened by swampy 



conditions, entirely free from gravel 1 to 8 feet. 



No. 2. Yellow clays, abounding with gravel, with occasional bowlders, often 

 constituting the surface instead of 1. Thickness seldom ex- 

 ceeding 10 feet. 



No. 3. Forest soil and bog iron ore. 



No. 4. Blue bowlder clay, or hard-pan. 



The white clay of the above section is a somewhat localized deposit, 

 but one that is spread over a wide area. In Clarke county it is called 

 the Springfield clay, and has been worked as a brick and tile clay for 

 3 



