226 On tfu Surfaci Geology of tht Basin of the 



nal and lateral moraines. I have, however, disproved, as 1 

 think, this theory of their transportation in a paper published 

 Borne years Bince (Notes on the Surface Geology of the Basin 

 of the Great Lakes. Proc. Bost. Nat. IIisr.Soc.18G3), in which 

 it is urged that the continuous sheel of the Erie clays upon 

 ■which they rest, and which forms an unbroken belt between 

 them and their place of origin, precludes the idea that they 

 have been transported by any ice-current or rush of water 

 moving <>ver the glacial surface; as either of these must have 

 torn up and scattered the soft clays below. 



There is, indeed, no other conclusion deducible from the 

 facts than that these sands, gravels, granite ami greenstone 

 boulders — masses of native copper, &c, which compose the 

 superficial Drift deposits — have been floated to their resting- 

 places, and that the floating agent has been ice, in the form of 

 icebergs : in short, that these materials have been transported 

 and scattered over the bottom and along the south shore of our 

 ancient inland sea, just as similar materials are now In 

 scattered over the banks and shores of Newfoundland. 



If we restore in imagination this inland sea, which we have 

 proved once tilled the basin of the lakes, gradually displacing 

 the retreating glaciers, we are inevitably led to a time in the 



tory of this region when the southern shore of this sea was 



formed by the highlands of Ohio, &c, the northern shore a 

 wall of ice resting on the hills of crystalline and trappean rocks 

 aln.ut Lake Superior and Lake Huron. 



From this ice-wall masses must from time to time have 

 been detached, jusl as they are now detached from the Ilum- 

 boldt Glacier, — and floated off southward with the current, 

 bearing in their grasp Band, gravel, and boulders whatever 

 composed the beach from which they -ailed. Five hundred 

 mile- Bouth they grounded upon the southern Bhore : the hi 

 lands of now Western New Fork, Pennsylvania, and Ohio, or 

 the shallowsof the prairie region of Indiana, Illinois, and Iowa ; 

 re melting away and depositing their entire loads,— as I 



