266 J. W. GOLDTHWAIT GLACIATION IN THE WHITE MOUNTAINS 



Agassiz, this glacier, after descending the side of Lafayette, crossed the 

 Franconia Valley and was thick enongh to overtop the ridge between 

 Mount Agassiz and Strawberry Hill (see plate 13) ; so that it flowed 

 northward over Bethlehem, descending a mile or two farther before it 

 halted at the lines of moraine. In other words, this glacier would have 

 followed the ravine of Lafayette Brook in a northwestward direction 

 nearly to the foot of the mountain, then would have turned abruptly out 

 of its valley, pursuing a northeasterly course across the undulating Gale 

 River lowland ; would have pushed over the Mount Agassiz ridge througb 

 a col at least 800 feet above the Gale River country, and thence would 

 have reached down over Bethlehem in a path transverse to the Ammo- 

 noosuc Valley, stopping near the river. Such a course would, have been 

 entirely disobedient to topography. A glacier or a group of glaciers, 

 heading on Mount Lafayette and Mount Garfield, would naturally con- 

 tinue the downhill course past Franconia village instead of leaving it to 

 pursue an uphill path across country to Bethlehem. Before it could pass 

 over the Mount Agassiz ridge the glacier would have had to fill the Gale 

 Biver basin to a height of more than 800 feet above its floor, east of 

 Franconia, forming an extensive sheet or lakelike expanse of ice, whose 

 main outlet would be northwestward past Franconia to North Lisbon. 

 Agassiz says, indeed, that 



"Those familiar with the topography of the Franconia Range, and its rela- 

 tion to Picket Hill and the slope of Bethlehem, will at once perceive that the 

 glacier which deposited the front moraine to the north of Bethlehem village 

 must have filled the valley of Franconia to and above the level of the saddle 

 of Picket Hill, making it at least 1,500 feet thick, if not more; thicker, in 

 short, than any of the present glaciers of Switzerland." 5 



Between such a glacier and the well contained, methodical valley 

 glaciers of the Alps the resemblance is slight indeed. Here, as in subse- 

 quent literature on local glaciers of the White Mountains, one sees a 

 tendency to overlook the differences between valley glaciers and ice-sheets. 

 From Agassiz's comparison of the moraines of Bethlehem with those of 

 the Rhone, one would expect to find narrow, steep-sided ridges, arranged 

 in concentric curves on lines of recession of an ice-tongue; but he does 

 not definitely describe their form and trend and does not map them. He 

 offers no evidence of striation by the local ice movement, and, although 

 he reports that the southward movement of rock material by the regional 

 glaciation is everywhere plain and unmistakable, he offers no definite 

 proof that any drift boulders have been moved northward by the local 

 glaciation. He says that "a careful examination of these [erratic boul- 



B Op. cit., p. 165. 



