336 
GEOLOGY OF THE FOURTH DISTRICT. 
masses of ice. The facts observed, which establish the proposition of a low limit of perpetual 
frost, with a luxuriant vegetation, and islands covered with eternal snow, while the sea in 
the same latitude swarms ‘with living creatures,’ can be applied to this portion of the world 
as well as to Europe, and furnish us with the same arguments in explanation of the transport 
of boulders. 
Let us now go back to the consideration of the condition of these boulders, and their relative 
situation to other superficial detritus, and we shall find that there can be no explanation offered 
of their mode of transportation, except during a time when the whole surface was covered by 
water. Had they been transported by a powerful current over the bottom, (which cannot be 
supposed from the inequalities of the surface,) all the older drift would have been removed at 
the same time, and instead of finding them as we now do mostly upon the surface, they would 
have been imbedded indiscriminately in the superficial detritus, and there would have been no 
means of recognizing the products of different periods. 
In order to allow of a sufficient depth of water for the transport and deposition of these 
boulders in the places we now find them, it would require a depression of the country from 
five hundred to two thousand feet below its present level. This greatest depression would 
cover nearly all of the middle and southwestern portions of New-York, and the whole extent 
of country occupied by the Great lakes, a large portion of Canada and the Western States. 
Indeed, allowing the relative elevation of different portions to have remained the same, which 
as regards New-York is doubtless true, the whole of that portion of North America east of 
the Rocky mountains would be one great ocean, with numerous and thickly scattered islands. 
The mountain chains of New-England and New-York would form long ranges of islands 
rising from the ocean to two and three thousand feet above its level, their sides covered with 
perpetual snow and glaciers, and their bays terminated by cliffs of ice, from which detached 
masses floated off, bearing with them boulders and fragments of rock.* These would be 
transported in every possible direction by the ocean currents ; and wherever the mass became 
stranded, or when it passed into warmer latitudes, its load of earth and rocks would be 
deposited. 
To a certain extent, this view is corroborated by the dispersion of the boulders in New- 
York; for we find them on every side of the great primary nucleus before noticed, and those 
found many miles north of this point are undistinguishable from many of those at the south. 
Still it must be acknowledged that the greater number seem to have been transported south¬ 
ward, probably owing to the existence of a polar current as in the present ocean.f It is not 
only probable, but it can be demonstrated, that this dispersion of the boulders and fragments 
continued for a long period, and while the land was rising from the ocean, and the gradual 
* See Darwin’s Journal, page 291 et seq. 
f I am informed by Dr. Emmons, that although there is no lithological difference in the transported blocks on the St. Lawrence 
at the north and northwest, as well as at the west and southwest, of the Great Primary region of New-York, still they diminish 
rather than become more numerous on approaching the base of these mountains, while the reverse is true when we attempt to 
trace their origin from the south. 
