70 NEW YOUK STATE MUSEUM 



Fix)m the i>oint of view of tlie larger features of relief, this 

 seeond segment of the lludsou valley is marked by the two great 

 valleys into which ii opens on the west along the strike of the 

 Hudson shales and sandstones, the one in the valley of the 

 Mohawk IxHween the Adirondacks and the Catskills on the north, 

 and the other that of the Walkill between the southeastern lx)rder 

 of the plateau region and the Highlands on the south. 



The third division, the shortest of all, comprises the Highland 

 canyon of the Hudson. It is a region of moderately high relief, 

 comparable in geologic structure to the Adirondack region. This 

 portion of the river valley will be referred to as the Highland- 

 Hudson. 



The fourth segment of the river includes the region south of 

 the Highlands to the sea. It is a region of ancient and meta- 

 mor])hic Paleozoic rocks on the east and of mainly Triassic rocks 

 on the west. It may for convenience be known as the Lower 

 Hudson. 



For geologic reasons it is convenient to recognize in an ancient 

 now submerged channel traversing the continental shelf to the 

 southeastward of New York harbor a possible fifth segment of the 

 Hudson valley, which may be termed the Submarine Hudson, but 

 to what extent this is excavated in bed rock is not known. 



At the northern border of the Fort Edward district, two nar- 

 row defiles unite the Hudson valley with that of Lake Champlain; 

 one of these is occupied by Lake George; the other, the valley of 

 Wood creek, directly drains the northern half of the Fort Edward 

 district into the Champlain valley. 



The divide between the Hudson waters and those of Wood 

 creek east of Fort Edward is 147 feet above sea level. A depres- 

 sion of 200 feet in the region between Albany and the St Law- 

 rence river would convert the Hudson and Champlain valleys 

 into a navigable stniil having a depth sufficient for the largest 

 vessels. A depression of 150 feet at Fort Edward and northward 

 over the region to the St Lawrence and an elevation of an equal 

 amount a I New York city would reverse the flow of the Hudson 

 in I he lower, middle and upp(M' sections and turn the drainage 

 into the St Lawrence gulf. 



