3 i6 POPULAR SCIENCE MONTHLY 



A ready explanation of the origin of this newest Pleistocene deposit (i. e., 

 that of the Hudson and Lake C'hamplain districts) suggests itself when we con- 

 sider the nature and energy of the crustal movements which lifted the 

 Laurentian clays and sands to a height, in one locality at least, of not less 

 than five hundred feet, and which drained wide tracts of the upper Laurentian 

 Lakes. 



The mere agitation or pulsating movement of the crust, if accompanied 

 by any permanent uplift of the land, would suffice, we would think, by lashing 

 the waters of the tidal estuaries in one quarter and the lakes in the other, to 

 strew a portion of the older drift bordering all those basins in wide dispersion 

 upon the top of the more tranquil sediments. But if such a pulsation of the 

 crust were accompanied by successively paroxysmal liftings of wide tracts of 

 the land, then the inundation would take the form of stupendous currents, the 

 strewing power of which would be adequate to any amount of superficial trans- 

 portation, even to the remote transportation of the larger erratics. 



In 1861 the Natural History Survey of Maine was inaugurated and 

 C. H. Hitchcock was placed in charge of that portion relating to geol- 

 ogy. Of his work, only that relating to glaciers concerns us here. 

 He noted that the fossiliferous marine clays which were regarded as 

 of the same age as similar deposits along the St. Lawrence and Cham- 

 plain valleys and referable to the terrace period, sometimes underlay a 

 coarse deposit referable to the modified drift. Without committing 

 himself definitely on this point, he suggested the possibility, therefore, 

 of a recurrence of the drift agencies, that is, a period of second drift, 

 as had the elder Hitchcock fifteen years earlier. 



The drift period itself, according to Hitchcock's view as here ex- 

 pressed, was inaugurated by a depression of this portion of the con- 

 tinent amounting to at least 5,000 feet below that of to-day, and it 

 was during this period of depression and reelevation that the drift 

 deposits were formed through the joint agency of icebergs and glaciers. 



In 1862 J. S. Newberry expressed his views on glaciers in an article 

 on the ' Surface Geology of the Basins of the Great Lakes.' After 

 reviewing the surface conditions as he saw them, he came to the con- 

 clusion that, at a period corresponding in climate, if not in time, with 

 the glacial epoch of the old world, the lake region, in common with all 

 the northern portion of the American continent, was raised several 

 thousand feet above the level of the sea. This was to him the glacial 

 period, during which the surface of the country was planed down and 

 the deep fiords along the Atlantic coast formed. This was followed 

 by a period -of depression, when all the basin of the Great Lakes was 

 flooded with fresh water, forming a vast inland sea in which the lam- 

 inated blue clays (the oldest drift deposits) were precipitated. 



Subsequent to this deposit of blue clay an immense quantity of 

 gravel and boulders was transported from the region north of the Great 

 Lakes and scattered over a wide area south of them. This he regarded 

 as due to floating ice and icebergs. 



It would seem that, if one were looking for original observations 

 on drift phenomena, he might turn with safety to the writings of the 



