116 THE GLACIAL LAKE AGASSIZ. 



erosion. Killington Peak, 4,221 feet high, has similar rounded outlines, 

 forming a "well-defined northern stoss side;" and Mr. Himgerford observed 

 numerous small bowlders of foreign rock within 20 feet of the highest point. 

 He concludes that all these summits, the highest in Vermont, were enveloped 

 by the ice-sheet. 



The glacial cuiTent crossed the Green Mountain range from northwest 

 to southeast and south. It transported bowlders of the Burlington red 

 sandstone across the range near Camels Hump, M^here they were carried 

 upward 3,000 feet above their source, and deposited them in the Quechee 

 Valley, near the Connecticut River, and in Hanover, N. H., about 60 miles 

 from their starting point. 



The Adirondack group culminates in Mount Marcy or Tahawus, 5,344 

 feet above the sea; and Mount Mclntyre, at 5,113 feet, is next in elevation. 

 Mr. Verplanck Colvin, in charge of the Adirondack Survey, states that the 

 summit of Marcy is contrasted with the other high peaks in its being desti- 

 tute of glacial drift; but its embossed and rounded ledges, as he observes, 

 indicate glacial erosion there, although its strife have been obliterated by 

 weathering.^ This summit lies about 125 miles west and a few miles south 

 of Mount Washington, and its distance north from the terminal moraine on 

 Long and Staten islands is about 235 miles. The average slope of the sur- 

 face of the ice-sheet from its termination to the Adirondack Mountains was, 

 therefore, not less than 23 feet per mile; and from the Catskills, where the 

 upper limit of glaciation is known, it was not less than 17 feet per mile. 

 How much it may have exceeded these figures can not be determined, but 

 what we know of Katahdin and Washington shows that the peak of Marcy 

 doubtless lacked only a little of rising above the ice-sheet at its time of 

 maximum thickness. In this connection it is to be remarked that the 

 change from a northward ascent of aljout 30 feet per mile south of 

 the Catskills to an average of 17 feet per mile, or slightly more, for the 

 next 130 miles to the Adirondacks is analogous with the slopes of the 

 Greenland ice-sheet, and with the northward ascent of the ice -surface 

 assumed by Dana in the computation before mentioned, namely, an aver- 



' Seventh Annual Report of the Topographical Survey of the Adirondack Region, to the 

 year 1879. 



