ANCIENT WATER LEVELS OP CHAMPLAIN-HUDSON VALLEYS 245 



Subsequent to the invasion by the sea, the land began to rise 

 on the north and to sink on the south, a movement which is, 

 according to the evidence obtained by Gilbert and others in 

 the Great Lake district, and by Cook and others along the coast 

 east and south of New York, still going on. In the valley of Lake 

 Champlain we find the indisputable evidence of uplift as high 

 as marine shells occur. About the mouth of the Hudson we 

 observe evidences of recent sinking and though we can not, 

 from what we see there, determine how long the depression has 

 been going on, it would seem as if the land must have gone as 

 far beneath the sea at that end of our line of ancient water 

 levels as it has risen out of the sea on the far'north. 



POSTSCRIPT 



If the sections of the Hudson river bed near New York city pre- 

 sented by Professor Hobbs^ in a recent paper include borings to 

 bed rock rather than boulders, it would appear for the first time 

 that the Hudson gorge at the latitude of New York city is not 

 more than perhaps 350 feet deep beneath sea level; but the evi- 

 dence is as yet by no means conclusive on this point. 



^Hobbs, W. H. Origin of the Channels surrounding Manhattan Island, 

 New York. Geol. Soc. Am. Bui. 1005. 16:151-82. See fig. 22-24 and 

 p.176-79. 



