62 AN OUTLINE OF THE 



the present time that the minute records of slight and 

 brief oscillations can be detected. The moderate depres- 

 sion by which our lower valleys have been, as we shall see, 

 drowned into bays, and the lesser elevation by which our 

 coastal slope has risen with a half-smooth sea cover on its 

 back are important to us, not by reason of their magnitude 

 or their duration, but simply by reason of their recency. 

 They must not be regarded as exceptional, but only as 

 giving indication of the uneasiness that most likely always 

 has and always will characterize the land. 



There is nothing on Mount Desert, or on the coast of 

 Maine, that suffices to define the geological date of the 

 elevation by which the two cycles of denudation just 

 described were separated ; yet when the field of inquiry 

 is extended so as to include all parts of the uplifted 

 peneplain, which is found to spread far to the southwest, 

 even to Alabama, its denudation may be correlated with 

 the deposition of various fossiliferous sediments, and thus 

 the completion of the peneplain may be placed in its 

 proper position in geological chronology. Strata of late 

 Cretaceous age in New Jersey are found overlapping the 

 seaward margin of the peneplain ; hence it is believed to 

 have been fairly well completed in late Cretaceous time ; 

 and the period of its elevation and consequent etching is 

 regarded as post-Cretaceous, or somewhere in the Tertiary 

 period. This is manifestly rather indefinite ; future inves- 

 tigations will probably define it more sharply ; but it is a 

 significant step in the right direction. Before this small 

 step was made, the date of the denudation of New Eng- 

 land was entirely unfixed, and very diverse views were 

 held on this subject. The making of the peneplain was 

 by some thought to be as old as the red sandstones of the 

 Triassic formation in the Connecticut valley ; and the 

 valleys were considered by others to be as young as the 

 time of the ice invasion, to whose erosive powers they 



