stood, being attributed to various causes, and to an aggregation 

 of conditions. But the fact remains that at that time there 

 was a marked elevation of the Laurentian area, which, is in 

 itself, a strong factor in the production of a severer climate. 

 The climatic condition of the regions north of the great lakes, 

 about Hudson's Bay and Labrador, were favorable at that time 

 for continual snows, which condition existed through long ages. 

 The short summer suns had little effect in dissipating them, 

 but reduced the vast snow field to glacial ice. And as it began 

 to pile up to thousands of feet in thickness, the known glacial 

 movements commenced, and the great ice flow started south- 

 ward. The ice mass being of great weight, and frozen solidly 

 to the surface upon which it rested, in its slow and tedious 

 motion onward, it carried or dragged everything movable with 

 it. The under surface being literally a stony mass, as it moved 

 onward it scoured, grooved and polished every surface over 

 which it passed, leveling and pushing onward all loose earthy 

 or rocky material found in its pathway. The great creases or 

 channels in the surface rock produced by stream erosion, were 

 partially obliterated by glacial erosion and partially filled by 

 glacial rubbish. As the ice sheet approached and passed into 

 the valleys of the great lakes, its lower margin became lobated, 

 and each lobe took a course largely in the direction of the lake 

 valleys, but as they emerged, they began to coalesce, forming 

 again an almost unbroken front, pushing onward to the south 

 with its load of boulders, gravel, sands and clay. As the ice 

 sheet traveled south to lower latitudes it was gradually approach- 

 ing a warmer climate, where the loss by melting at its border, 

 and from its surface, equalled its production at the ice center. 

 This balance of energies brought its onward movement to a 

 close, and caused the ice border to remain stationary, probably 

 for thousands of years. At this fixed point the ice yielded up 

 its glacial waters which rolled onward to the sea through the 

 great central water-way, the Mississippi river. The Laurentian 

 ice sheet was practically a homogeneous mass, composed of ice, 

 rock, clay, sands and gravel. The immense forests covering 

 the surface of the country, were also swallowed up and ground 



