POST-TERTIARY PERIOD. 545 



sands of tons' weight might have been lodged on the tops of ridges, 

 miles away from their place of origin. Moreover, the Green Moun- 

 tain side of the Connecticut valley would naturally have given that 

 more eastern direction to the striee observed about the higher sum- 

 mits (p. 540), because the general slope is eastward; while below 

 these more elevated points the southward inclination of the great val- 

 ley itself would have directed the movement of the extended glacier. 



In the vicinity of Penobscot Bay, Maine, according to J. De Laski, 

 there are groovings, polishings, and other related effects, in perfec- 

 tion, which prove beyond question the former existence there of 

 an extensive glacier, — probably one of the many terminations of 

 the continental glacier. 



Switzerland, besides its examples of small modern glaciers, affords 

 evidence of a great glacier in some former time which serves to 

 illustrate the condition in the Glacial epoch in America. At the 

 time referred to (supposed to be later than the Glacial epoch), a 

 glacier stretched from Mt. Blanc and other Alpine heights over 

 the Swiss plains to the Jura Mountains on the borders of France, 

 having underneath it the sites of Lake Geneva, Lake Neufchatel, 

 and other Swiss lakes. The declivity of the Juras facing the Alps 

 was covered, to half its height in many places, with the boulders 

 that were transported by the ice ; and one of them— the Pierre-a-bot, 

 a mass of granite (or more properly protogine) — is 62 feet long by 48 

 broad, and contains about 40,000 cubic feet, equivalent to a weight 

 of 3000 tons. The transportation of this and other such blocks has 

 been attributed to icebergs. But Guyot, by an extensive explora- 

 tion of the mountains and plains, succeeded in tracing out the lines 

 of moraines across the plains; $nd, by observing the kinds of rocks 

 characterizing the several lines, followed each up to the peak or 

 peaks in the Alps from which it was derived. He proved in this 

 way that the Pierre-a-bot and other similar masses of the same part 

 of the Juras came from Mt. Blanc, and that the red sandstone 

 boulders accompanying the granitic on the Juras were from the 

 Aiguille Rouge, a neighboring summit. By this means he found 

 that the order of succession in the peaks is repeated in the order of 

 the lines of rocks over the lowlands, just as would have been the fact 

 had these lines been originally the moraines of a glacier. He fur- 

 ther ascertained that the great glacier from Mt. Blanc which bore on 

 its surface for ninety miles the Pierre-a-bot, and multitudes of other 

 masses, small and great, left the vale of Chamouni (the present 

 terminus of the Mt. Blanc glaciers) by the valley of the Trient, and 

 so passed northward into the valley of the Ehone ; thence it spread 

 still northward and westward across the Lakes of Geneva and Neuf- 



36 



