282 J. W. GOLDTHWAIT GLACIATION IN THE WHITE MOUNTAINS 



Ammonoosuc Valley while the ice-masses still lingered there, although 

 the main body of the ice-sheet had retired to the north side of the water- 

 shed. On an earlier page it was pointed out that the thick deposits of 

 stratified drift in the kame moraines north of Bethlehem suggest wide- 

 spread ponding of the Ammonoosuc waters by an ice-sheet which was 

 retiring northward. Similarly the great pitted plain and kame fields of 

 Carroll seem to require an ice-dam so placed as to hold the waters of the 

 Ammonoosuc up to or above the level of the floor of the Beech Hill- 

 Cherry Mountain pass. The Carroll deposits record an earlier, and the 

 Bethlehem moraine a later, stage in the withdrawal of this great ice-dam 

 from the temporary Lake Ammonoosuc. The theory of Doctor Upham, 

 that the Canadian ice had withdrawn from the district north of the 

 mountains and had left a local ice-cap on the highlands, with a reentrant 

 angle near Cherry Mountain, offers no reason for static waters in which 

 delta-like plains might accumulate; for there would be nothing to pre- 

 vent the free flow of waters northward by Carroll Stream past Whitefield 

 to the Connecticut Eiver near Lancaster (see plate 13). The presence of 

 so much stratified drift, therefore, as well as the southward slope which 

 distinguishes its surface and the southward decrease in the coarseness of 

 material, is reason for supposing that the ice-sheet concerned in its con- 

 struction was the Canadian sheet on the north and not a local White 

 Mountain ice-cap on the south. 



DISPERSION OF BOULDERS NEAR THE TWIN MOUNTAIN HOUSE 



It is pertinent now to examine the evidence first reported by Hitch- 

 cock and later used by Upham, that boulders near the Twin Mountain 

 House have been transported down Ammonoosuc! Valley by ice moving 

 outward from the White Mountains. Hitchcock's statement is as follows : 



"In the fields east of the Twin Mountain House there are hundreds of 

 boulders of Mount Deception granite, often 12 feet in length. The underlying 

 rocks, for the four or five miles distance between the Twin Mountain House 

 and Fabyan's, are of very different material. Hence this is an example of 

 materials transported westerly a distance of four miles. This cannot have 

 been done by water — the blocks are too large. A local glacier sliding over the 

 more ancient drift must have been the agent of transportation. This lateral 

 moraine east of the Twin Mountain House is quite conspicuous, and the most 

 readily accessible of any examples known. It may be seen from the train, a 

 short distance east of the station." 1S 



On reading this paragraph, it was obvious that although these blocks 

 might have come westward from Mount Deception, over areas occupied 

 by different types of rock, as Hitchcock supposed, it was at least equally 

 possible that they might be found to have come in a southeastward course 



18 Op. cit, p. 242. » 



