-1830] WRITINGS OF JOSEPH HENRY. 31 



water, lying in an apparent rend in the adjacent moun- 

 tains ; is thirty -four miles long, and from one to three miles 

 wide. It discharges its waters into Lake Champlain, through 

 a descent of nearly 200 feet. Lake Champlain, which forms 

 the most important part of the upper sub-basin, is 109 miles 

 long, and from one-half mile to twelve miles wide ; its depth 

 nearly corresponds to that of Huron and Michigan ; while 

 its surface is elevated only 93 feet above the level of tide 

 water. Surrounded by imposing mountain scenery, the 

 traveller on this lake imagines himself raised to Alpine 

 heights, and can scarcely be convinced that a descent of less 

 than one hundred feet would depress him to the level of the 

 ocean. Lake Champlain is connected with the river St, 

 Lawrence by the Chambly river on the north, and with the 

 Hudson river on the south, by the artificial communication 

 of the Champlain canal. The intervening distance between 

 the Hudson river and the lake is only 22 miles ; but the 

 whole length of the canal, from its junction with the Erie 

 canal, is 64 miles, 39 of which is along the side of the river. 

 The other division of the Hudson and Champlain valley, 

 is the deep basin of the Hudson ; and this may again be 

 described as consisting of two subdivisions. The first of 

 these includes the lower valley of the Mohawk, and the 

 slopes of land on each side of the Hudson, from Glen's falls 

 to the entrance of the Highlands near Newburgh. The 

 sandy plain between Albany and Schenectady, is an upper 

 shelf of the lower valley of the Mohawk, the southern bound- 

 ary of which is a continuation of the Catskill mountains, 

 and is seen in travelling between these cities, stretching 

 along the horizon in a northwesterly direction towards the 

 Mohawk river. This plain has a mean elevation of 320 

 feet, and suddenly declines into the valley of the Hudson by 

 a precipitous step nearlj^ parallel to the river. The capitol 

 at Albany is built on the very edge of this step ; and the 

 Mohawk, in passing over the same depression, forms the 

 Cohoes or great fall of the river, A similar shelf exists on 

 each side of the Hudson, from Albany down to the High- 

 lands. The country rises abruptly from tlie river to upwards 



