41 



18. — A scratc^ied limestone pebble taken from a 

 glacial soil. 



boulders will doubtless be found ; and if they are compared with 



the solid or bed rock of the country, which underlies the soil (Fig. 15) 



some of them will be found 

 to be quite different from it. 

 For instance, where the bed 

 rock is shale or limestone, 

 some of the pebbles will no 

 doubt be granite, sandstone, 

 etc. If you could explore, 

 yon would iind just such 

 rocks to the north of you, 

 perhaps one or two hundred 

 miles away in Canada ; or, 

 if your home is south of" the 

 Adirondacks, you might 

 trace them in those moun- 

 tains. 



On some of these pebbles, 

 especially the softer ones 



such as limestone, you will find scratches, as if they had been ground, 



forcibly together (Fig. 18). Looking now at the bed rock in some 



place from which the soil 



has been recently removed, 



you will find it also scratched 



and grooved (Fig. 19) ; and 



if you take the direction of 



these scratches with the 



compass, you will find that 



they extend in a general 



north and south direction, 



pointing in fact in the same 



direction from which the 



pebbles have come. 



All over northeastern North America and northwestern Europe 



the soil is of the same nature as that just described. In our own 



country this kind of soil reaches down as far as the edge of the shaded 

 28 433 



19. 



T7ie grooved bed rock scratched by the move- 

 ment of tTie ice sheet over it. 



