584 W. M. DAVIS DATES OF TOPOGRAPHIC FORMS. 



not, they constitute so great an addition to our previous knowledge of the 

 country that they are invaluable aids in geological or geographic study. 



A result of interest that will be obtained from coloring maps by topo- 

 graphic dates is the relation of the origin of our geographic forms to their 

 present settlement and to the occupations that they define. The Cretaceous 

 uplands are largely forested, and support a scattered, rural population ; the 

 Tertiary valleys are lines of travel, the seats of towns and villages ; the low^- 

 lands of the same date include our richest agricultural districts. The post- 

 Tertiary trenches are as yet generally too narrow for occupation. Near the 

 coast the oscillations of level have determined the harbors of New Eng- 

 land, and the " fall-line " displacement is well known in locating many of 

 the larger cities of the middle Atlantic states. 



Harvard College, Cambridge, Mass. 



