THE GLACIAL HYPOTHESIS 3°* 



wide dispersion of drift boulders over the northern part of the country, 

 although the glacial character of the same was not dreamed of. 



The paper, so far as existing literature shows, caused little discus- 

 sion, and we have next to refer to observations by Dr. Samuel Akerly, 

 who, in 1810, published in Bruce's American Mineralogical Journal 

 a geological account of Dutchess County, New York. After referring 

 to the Highlands and the country to the northward, he described the 

 southern part — that upon which the then existing city was built — as 

 composed of an alluvion of sand, stone and rocks. This he looked 

 upon as a recent deposit, ' subsequent to the creation and even the 

 deluge.' The manner in which this material was deposited he de- 

 scribed in the following language: 



After the waters of the deluge had retired from this continent, they left a 

 vast chain of lakes, some of which are still confined within their rocky bar- 

 riers. Others have since broken their bounds and united with the ocean. The 

 Highlands of New York was the southern boundary of a huge collection of 

 water, which was confined on the west by the Shawangunk and Catskill moun- 

 tains. The hills on the east of the Hudson confined it there. When the hills 

 were cleft and the mountains torn asunder, the water found vent and over- 

 flowed the country to the south. The earth, sand, stones and rocks brought 

 down by this torrent were deposited in various places, as on this island, Long 

 Island, Staten Island and the Jerseys. This opinion, he added, is mostly 

 hypothetical, because unsupported by a sufficient number of facts. 



A candid acknowledgment upon which the author is to be congratu- 

 lated ! 



"Whose was the master mind that first conceived of this great barrier 

 which held back the flood of waters, so long made responsible for the 

 drift, I have not been able to ascertain. The theory is, however, given 

 in greatest detail by Dr. Samuel L. Mitchill in his ' Observations on 

 the Geology of North America,' published in 1818. 



It was Mitchill's idea that the Great Lakes are the shrunken rep- 

 resentatives of great internal seas of salt water, which ultimately broke 

 through their barriers, the remains of which he thought to be still 

 evident. One of them he wrote, seemed to have circumscribed the 

 waters of the original Lake Ontario and to be still traceable as a 

 mountainous ridge beyond the St. Lawrence in upper Canada, passing 

 thence into New York, where it formed the divide between the present 

 lake and the St. Lawrence and continued to the north end of Lake 

 George, apparently crossing the Hudson above Hadley Falls. Thence, 

 he believed it to run toward the eastern sources of the Susquehanna, 

 which it crossed to the north of Harrisburg, and continued in a south- 

 easterly direction until it entered Maryland, passing the Potomac at 

 Harpers Ferry into Virginia, where it became confounded with the 

 Allegheny Mountains. 



To appreciate Mitchill's views, then, we have to imagine this now 

 broken and gapped ridge as continuous. A time came, however, when 

 at various points it gave way, the pent-up waters rushing through and 



