CENOZOIC ERA. AGE OF MAMMALS, 387 



terials may be irregularly stratified and cross-laminated, 

 as if by water running beneath,, or from the snout of a 

 glacier. In places the laminae may be twisted and crum- 



Fio. 846. Subangular stone. (After Geikie.) 



pled, as if by a glacier pushing along on a mud surface. 

 In still other places, especially west of the Appalachian, 

 the upper part is more widely stratified. But this may 

 belong to a later epoch (Champlain). 



Bowlders. Over all are scattered rock-fragments and 

 bowlders, of all sizes, both angular and rounded some- 

 times as thick as hailstones after a storm, and actually 

 cumbering the earth. These bowlders, whether imbedded 

 in drift or scattered on the surface, are usually entirely 

 different -from the country-rock. Great blocks, of thou- 

 sands of cubic feet, are often seen perched where they do 

 not belong, as if stranded by glacier or iceberg. The par- 

 ent ledge from which they were torn can often be found, 

 and thus the direction of their transport is known. By 

 this means it has been ascertained that from the Cana- 



