28 8 Tertiary. 



this drainage system, vast internal lakes were formed hy the elevation 

 of the western mountain chains, which overflowed and drained them- 

 selves across the central part of the continent, and produced, as we 

 will see, in the sequel, all the phenomena of the drift. 



As heretofore, we will follow the historical and chronological order 

 of discovery as far as practicable. 



.y In 1817, Dr. Daniel Drake,* of Cincinnati, wrote an essay upon the 

 alluvial and drift formations of Ohio and the surrounding countr3^ 

 The letter was not published, however, until 1825. He supposed that 

 the gravel and sand which spreads itself over the western part of Ohio, 

 and is not found over eastern Kentucky, is the result of an inundation, 

 having its origin north of the lakes, and that the large bowlders and 

 blocks of stone, distributed over the country, were transported by large 

 fields of ice and icebergs, which floated from the arctic regions during 

 this inundation. He said, the ice to which they were attached could 

 not of course pass a certain latitude ; and from the great increase of 

 these masses as we advance toward the north, it would seem that 

 many of the icebergs suffered dissolution long before they arrived at 

 this locality. 



In 1820, Caleb Atwaterf stated, that an arrow-head was found in 

 the alluvium, when digging a well at Cincinnati, 9U feet below the sur- 

 face ; that a human skeleton was found in the alluvium at Pickaway 

 plains, 17^ feet below the surface, that could not have been interred 

 by human hands in that position ; and he figured and described a 

 human skull of a very low grade, which was found nine feet below the 

 surface, in such a position as to suggest its contemporaneity with the 

 drift era. 



In 1825, Sayers GazleyJ found fossil wood in Hamilton county, 

 Ohio, below the gravel, and intermixed with it and bluish earth, at 

 depths from 10 to 40 feet below the surface, and apparently where the 

 trees had originally grown. 



In 1838, Prof. James Hall§ observed the indications of diluvial 

 action, in western New York, in the accumulations of gravel, sand, 

 pebbles and bowlders of all dimensions strewn over the surface. In 

 some places slight scratches were observed on the rocks, while in others 

 they were numerous and deep, often extending for several feet, and in 



■■■ Trans. Am. Phil. Soc, vol. ii. 

 f Am. Jour. Sci. and Arts. 

 X Ibid. 

 § Geo. Rep. N. Y. 



