W. UPHAM — FIORDS AND LAKE BASINS. 505 



along those twenty-five miles from 50 to 100 fathoms. The bed of the fiord, as de- 

 scribed by Lindenkohl, commences with a depth of only about 10 fathoms below the 

 general plain, or 60 fathoms below the sea level ; but the soundings in the fiord in- 

 crease to 200 fathoms within the first mile, and its deepest sounding, 474 fathoms, is 

 close to its outlet. "This outlet to the ocean," writes Lindenkohl, "is in the shape 

 of a bar with a depth of about two hundred fathoms. For half its length, from its 

 middle to the bar, this ravine maintains a vertical depth of more than two thousand 

 feet, measuring from the top of its banks ; these banks have a nearly uniform slope 

 of about 14°. It remains to be stated that the bottom and the sides of the ravine are 

 composed of a green sandy mud, and that the adjacent flats, unlike those of the sub- 

 merged channel, show the same material." 



This fiord under the sea demonstrates that the border of the continent in the vicinity 

 of New York has been uplifted 2,800 feet higher than now, while a large stream here 

 flowed down from the equally or perhaps more uplifted basin of the Hudson, proving 

 that the elevation affected a very extensive area. The date of this uplift is shown to 

 have been after the deposition of the Tertiary beds of New Jersey, in which the 

 channel and fiord are eroded ; and the length of time during which the land stood at 

 this height was manifestly short, geologically speaking, else the fiord would be much 

 longer, occupying the place of the comparatively shallow channel. 



When subsidence of the country ensued, a very massive bar was formed by coast- 

 wise wash across the mouth of the Hudson fiord, attaining a height of 1,000 feet above 

 its bottom, and the crest of this bar is now about 1,200 feet below the sea level. A 

 later stage in the subsidence, when the land was only about 200 feet above its present 

 height, is marked by the sand bar at the end of the submarine channel. From then 

 to the time of formation of the present bar the depression of the land seems to have 

 been too rapid to permit such accumulation ; but since the channel southeast of Sandy 

 Hook was submerged, a bar rising from 19 fathoms to 4 fathoms below present mean 

 sea level has been built up. By Mr. Lindenkohls computation, based on Professor 

 Cook's estimate that the present rate of subsidence of the coast of New Jersey is about 

 two feet in a hundred years, this bar represents a period of 4,500 years ; but the aver- 

 age subsidence may have been slower, allowing a considerably longer time. 



Combining this testimony of oscillations of the land with the records of the Glacial 

 period, whose terminal moraine, at the southern limit of the till and of glacial stri» 

 and glacially transported bowlders, forms the range of hills called the backbone of 

 Long island and thence reaches westward from the Narrows across Staten island and 

 northern New Jersey, we find their relationship to be as follows: Shortly before the 

 Ice age this area was greatly uplifted, holding an altitude a half mile or more above 

 its present height long enough for the Hudson to cut its now submerged fiord, twenty- 

 five miles long and three miles wide, in easily eroded sandy clays. This elevation into 

 the cold upper strata of the atmosphere may well have been the direct cause of the ac- 

 cumulation of the Quaternary ice-sheet, which covered the northern half of the conti- 

 nent, forming the terminal moraines and other drift deposits. Beneath the ice-sheet, 

 however, the land was depressed until, when the ice finally melted away, much of the 

 coast stood lower than now, as shown by fossiliferous marine beds overlying the glacial 

 drift in northern New England, New Brunswick, the valley of the St. Lawrence, 

 about Hudson's bay, and in Labrador and Greenland. The amount of this depression 

 increases from a few feet near Boston and Gloucester, Massachusetts, to .V_'(i feet at 

 Montreal, and 1,000 to 2,000 feet in Greenland and Grinnell Land. Though it v 

 probably induced by the pressure of the ice-weight, it does not appear to have been 



LXXV— Bri.i,. Gf...t,. Soc. Am., Vol. 1, 1889. 



