THE GEOLOGY OF NATURAL SCENERY. 24.1 



who would know it, infinite in the variety of its expression and 

 charming in the simplicity of its style. 



Among the varied scenes which charm the eye there are none 

 so pleasing as those which combine both land and water ; and the 

 vicinity of New York city, with its varied and rich combination 

 of water and landscape, will serve as a fitting example to intro- 

 duce the subject. 



In order to consider the origin and history of this scenery, it 

 is necessary to look backward a short distance in geologic time. 

 Ten thousand years or more ago the continental glacier extended 

 from the highlands of British America southward to Long Is- 

 land, and at its margin, where it may have been a thousand feet 

 or more in thickness, accumulated a mass of rock debris brought 

 in part from northern New York and New England. When the 

 advent of a warmer climate caused the ice sheet to retreat, its 

 terminal mass of debris, called by geologists the moraine, formed 

 a range of lofty hills, locally known on Long Island as the 

 '"backbone," and which crosses Staten Island, northern New 

 Jersey, Pennsylvania, and Ohio, continuing northwestward far 

 beyond the Mississippi. 



The land was then much depressed to the northward, and the 

 waters of the ocean communicated with New York Bay through 

 the valleys of the St. Lawrence, Lake Champlain, and the Hudson. 

 In place of Lake Champlain was a great estuary, its surface four 

 hundred feet above the present tide level, stretching from the 

 foothills of the Adirondacks on the west to the Green Mountains 

 on the east, and of which the beaches with their sea shells may 

 still be found. Into the estuary which occupied the valley of the 

 Hudson the streams from the surrounding country brought their 

 sediment, gradually forming deposits of clay and sand, while on 

 the outer shores of Staten and Long Islands the ocean waves 

 broke sixty feet or more above their present level. Gradually 

 the continent rose from its submergence, the elevation of the land 

 caused the ocean to retreat, and the Hudson, the Mohawk, and 

 their tributaries sought an outlet southward to the sea. The 

 rivers thus revived cut a channel in their seaward journey 

 deeper and deeper through the sand and clay deposited in the 

 Hudson Valley, and near the end of their united course carved 

 through the moraine a passage which we call the Narrows. 



When Long Island Sound is viewed from the Westchester 

 shore the lofty hills of the moraine form a most picturesque 

 background to the blue waters of that beautiful estuary which 

 but for the advent of the ice sheet would probably have been 

 separated from the ocean only by a low, sandy plain. From 

 the summit of the moraine in Prospect Park, Brooklyn ; from 

 Harbor Hill, or from any of the numerous eminences on Long 



VOL. SLVI. 19 



