POST-TERTIARY PERIOD. 549 



America these Champlain formations of all kinds over the continent 

 are so combined in system, both as to extent and elevation, that it is 

 generally not difficult to arrive at a right decision on this point. 

 There are many examples of the direct passage of the high plains 

 along a river into that of the lake, or into that of the sea-border, 

 where the river empties into the one or the other, in which the 

 mutual relations and dependence of the whole cannot be doubted. 



Besides these border formations of lakes, there are also, overlying 

 the Drift in many places, beds of marl or calcareous earth formed 

 from fresh-water shells in the ponds and smaller lakes of the epoch. 

 This shell-marl is of great value as a fertilizer. Beds of peat were 

 often in progress afterwards in the same ponds as they were gradu- 

 ally drained and became marshes. The shells are all of existing 

 species. 



In elevated regions without rivers or lakes, Hbeds of the formation 

 may sometimes be distinguished by a more or less perfect stratifica- 

 tion or regular arrangement of the surface-gravel, indicating the 

 former action of water. Such beds are sometimes called beaches and 

 attributed to sea-shore action, although containing no evidence of 

 this origin from marine remains or other satisfactory marks. They 

 are also termed, with a degree of propriety, modified drift. 



(c.) Sea-border formations. — On sea-shores, also, there are analogous 

 deposits, situated above the height at which accumulations are now 

 in progress. They often have the characters of the modern sea- 

 beach, and are then rightly termed ancient sea-beaches ; and the ter- 

 race, in such a case, about the mouths of rivers passes directly into 

 that of the river-border formation. In other places they resemble 

 more the shallow-water deposits of a coast. They often bear dis- 

 tinct evidence of their marine origin in the presence of marine 

 shells. Such beds have been observed near Brooklyn on Long 

 Island, where they contain shells and have a height of one hundred 

 feet above the sea-level ; at several places on the coast of New Eng- 

 land ; on the shores of Lake Champlain, at different heights, up to 

 393 feet above tide-level, and containing shells to a height of 325 

 feet ; on the borders of the St. Lawrence, with abundant marine 

 fossils ; near Quebec, Montreal, and on the Ottawa, to a height be- 

 tween 400 and 500 ; and beyond to Kingston. From this point the 

 same formations continue on, and border Lake Ontario, but they 

 are destitute of marine remains, — the waters of the river St. Law- 

 rence beyond having apparently prevented the farther ingress of 

 the ocean and of marine life. 



Similar beach formations, containing recent shells, occur in the 

 Arctic regions at various ♦places, as on Cornwallis and Beechey 



