SUBAERIAL AGENTS 



30; 



ware, and Chesapeake Bays. These estuaries show by their form 

 that they are river valleys invaded by the sea, and the channel of 

 the Hudson has been traced by soundings to the edge of the con- 

 tinental platform, one hundred miles out from Sandy Hook. 



The denuding action of the sea upon a depressed and irregular 

 coast-line is to reduce its irregularities, wearing down the islands, 

 cutting back the promontories, and filling up the bays and more 



FIG. 131. — Christiania Fjord, Norway. (Photograph by Libbey.) 



sheltered spots, and, if long enough continued, will result in the 

 same evenness of contour as is produced by the working of an 

 upheaved shore. 



The Subaerial Agents are those which operate over the entire 

 surface of the land. Their tendency is, in the first instance, to 

 carve out valleys and leave relative eminences standing, and thus 

 to increase the irregularity, or relief, of the land. This, however, 

 is merely a temporary stage, and if time enough be granted, these 

 agencies will sweep away the irregularities and plane the entire 

 region down to the base-level of erosion. 



