WARREN IP1IAM — RELATIONSHIP OF GLACIAL LAKES. 487 



and increasing from south to north, us shown by terraces and deltas of the glacial 

 lake .Hudson-Champlain, which were formed before this lake became merged in 

 lake Iroquois, was nearly 180 feet at West Point, 27-"> feet at Catskill, and 840 feel 

 at Albany and Schenectady* Farther northward, according to measurements by 

 Baron de < reer of the altitudes of the highest shore marks in the part of the Saint 

 Lawrence basin which was filled by the expanded lake Iroquois, the depression 

 was approximately 650 feet at St. Albans ; 625 feet on mount Royal at Montreal; 

 and 700 feet on the hills a few miles north of the city of Ottawa. From these 

 figures, however, both in the Hudson and Saint Lawrence basins, we must subtract 

 the amount of descent of the Hudson river, which in its channel outside the pres- 

 ent harbor of New York may probably have been once 50 or 60 feet in its length of 

 about 100 miles, as seems to be indicated by the height of terraces on Manhattan 

 island and in its vicinity. Before the time of disappearance of the ice-barrier at 

 Quebec this descent may have been diminished, or the seaboard at New York may 

 have sunk so as to bring the shore-line nearly to its present position; but the 

 Hudson valley meanwhile had been uplifted, so that an outflow from lake Iroquois 

 crossed the low divide, now about 150 feet above the sea, between lake Champlain 

 and the Hudson. This is known by the extension of fossiliferous marine deposits 

 along the lake Champlain basin nearly to its southern end, while they are wholly 

 wanting along all the Hudson valley. Indeed, the outflowing river from lake Iro- 

 quois, or the Hudson during the subsequent post-glacial epoch, channeled the lower 

 part of this valley to a depth of about 100 feet below the present sea-level, proving 

 that the land there, as Mr. Merrill points out, stood so much higher than now at 

 some time after the ice retreated. 



When lake Iroquois ceased to outflow at Rome and, after intervening stages of 

 .outlets existing for a short time at successively lower levels north of the Adiron- 

 dacks, began to occupy the lake Champlain basin, outflowing thence to the Hudson, 

 its surface fell by these stages about 250 feet to the glacial lake Hudson-Champlain, 

 which had doubtless reached northward nearly to the Saint Lawrence. After this 

 reduction of its level, lake Iroquois had a depth of about 150 feet over the present 

 mouth of lake Ontario, as shown by a beach traced by Mr. Gilbert, which thence 

 rises northeastward but declines toward the south and southwest. Its plane, which 

 is parallel with the higher Iroquois beaches, sinks to the present lake level near 

 Oswego, New York. Farther southwestward the shore of the glacial lake at this 

 lower stage has been since submerged by lake Ontario. The Niagara river was then 

 longer than now, and the lower part of its extent has become covered by the present 

 lake. From the time of the union of lakes Iroquois and Hudson-Champlain a 

 strait, at first about 150 feel deep, but later probably diminished on account of the 

 rise of the land to a depth of only about 50 feet, joined the broad expanse of water 

 in the Ontario basin with the larger expanse in the Saint Lawrence and Ottawa 

 valleys and the basin of lake ( 'hamplain. At the subsequent time of ingress of the 

 sea past Quebec the level of lake Iroquois again fell probably 50 feet or less to the 

 ocean level. The place of t he glacial lake so far westward as the Thousand islands 

 was then taken by the sea, with the marine fauna which is preserved in the Ledu 

 clays and Sn ncava sands. 



.1. s. Newberry, Popular Science Monthly, vol. \iii. 1n7*. pp.641 GGO; V. i II. Merrill, Am. Jouin. 



s.-i.. :;il series, vol. xli, 1891, pp. IG0-466; W. M. DaA i-. Proi dings "l the Boston Society of Natural 



History, vol. xxv, 1891, pp. 318-334; Warren Upham, Hull. G ol -■- Vm., vol. i. 1890, p. 5G6, and vol 

 2, L891, i'. 265, 



