DERELICTIONS OF THE HUDSON. 367 



the sand and gravel have been washed off, to Troy, and 

 the great falls of the Mohawk. The fine scenery along 

 the Hudson at Glen's and Hadley's falls, has been so ele- 

 gantly sketched by Mr. Milbert, that his paintings give 

 interest to geology. The descent of the river toward 

 tide-water at Troy, is interrupted by several smaller falls 

 and rapids running over layers of slaty rock. This con- 

 tinues until the Mohawk joins it from the west. Their 

 united current passes along without any memorable im- 

 pediment until it arrives at the Highlands, a range of 

 mountains crossing it a little to the southward of New- 

 burgh and Fishkill. They are composed chiefly of gra- 

 nite and gneiss, abounding in loose nodules and .solid 

 veins of magnetical iron ore. The width of the chain 

 may be rated at about sixteen miles. The height of the 

 most elevated peaks have been ascertained barometrically 

 by Captain Alden Patridge, of the corps of artillerists 

 and engineers. According to his observations, Butter- 

 Hill, on the west side of the river, is 1529 feet above 

 tide-water, and the new Beaco.n 1565 feet. 



This thick and solid barrier seems in ancient days to 

 have impeded the course of the water, and to have raised 

 a lake high enough to cover all the country to Quaker- 

 Hill and the Taconick mountains on the east, and to the 

 Shawangunk and the Catskill mountains on the west. 

 This lake may be calculated to have extended to the 

 Little Falls of the Mohawk, and to Hadley Falls on the 

 Hudson. Geometrical surveys, and geological facts, 

 countenance the belief, that a lake covered the whole 

 space between the mountains on the east side of lake 

 George and the Green Mountains in Vermont, and made a 

 continued body of water to lake Champlain, as far above 

 Montreal, as the foot of the aneient barrier already de- 

 cribed as having existed anciently at the Thousand 



