BETHLEHEM MORAINE 269 



prevailing condition. If that is so, the presumption is that the boulders 

 have been carried to their places by the ice-sheet. 



In Doctor Upham's paper of 1904 a wholly new conception of the 

 Bethlehem moraines was presented. Upham concurs in Agassiz's view 



"that the morainic drift . . . was brought from the south, being amassed 

 along the northern edge of ice fields that sloped down from the northern edge 

 of the Franconia and Twin Mountain ranges ; but I could not trace the many 

 and mainly parallel morainic ridges or series of knolls and hillocks which his 

 description led me to expect. Instead of separate and well defined small 

 frontal moraines, like those which I have seen in the glens and valleys around 

 Ben Nevis and Scrawfell, marking intervals of halting in the retreat of the 

 latest local glaciers, the ridged and knolly drift deposits north of Bethlehem 

 appear to me to be an indivisible and promiscuous morainic belt, running 

 there from east to west, with a width of one to one and a half miles, quite 

 like the typical moraines of the continental ice-sheet in their course through 

 Minnesota and adjoining States. . . . The morainic belt close north of 

 Bethlehem, which I then first examined, was found ... to have a con- 

 siderable extent from east to west in the Ammonoosuc Valley. Beyond that 

 portion, traced from the vicinity of the Twin Mountain House westward to 

 the south part of the village of Littleton, a distance of twelve miles, this 

 moraine doubtless turns to the southwest and south, and sweeps circuitously 

 around the highest ranges of the White Mountains, to connect again, from the 

 east and north, with the east end of the part so traced. Its small hills and 

 short ridges usually rise 15 to 30 or 40 feet above the intervening and adjoin- 

 ing hollows, but sometimes to heights of 50 to 100 feet ; and in many places, 

 as at Littleton, its accumulations are more massive than at Bethlehem. 



"The material of this belt is chiefly till, with some modified drift, as kames, 

 or knolls of gravel and sand. The contour is very irregular, in multitudes of 

 hillocks and little ridges, grouped without order or much parallelism of their 

 trends. Everywhere in and upon these deposits boulders abound, of all sizes 

 to rarely 5 or even 10 feet, or more, in diameter, being far more plentiful than 

 in and on the adjoining smoother tracts of till throughout this region." 13 



This interpretation of the topography and structure of the moraine by 

 one experienced in tracing morainic belts avoids the difficulties raised by 

 Agassiz's theory of a valley glacier; but it introduces a new problem of 

 scarcely less interest. If the Bethlehem moraine marks the border of an 

 ice-sheet, was it built at the southern edge of ice which still covered 

 eastern Canada and northern New England, having withdrawn from the 

 White Mountains, or was it built at the northern edge of a smaller, more 

 local ice-cap which covered the White Mountains, being supported by 

 local snowfall after the Canadian ice had withdrawn? As shown in the 

 quotation just cited, Upham adopted the latter view, influenced, it may 

 have been, by the idea that the superiority of altitude of these highest 

 mountains of New England would require a continuance of glacial climate 



13 Op. cit, pp. 10-12. 



