BETHLEHEM MORAINE 275 



matched in a strange and unaccountable mosaic, rarely obedient to the 

 laws of underground structure on the one hand or those of topography 

 on the other. It is a question whether an attempt to build up a complete 

 bedrock map in solid colors is justified in a region so generally concealed 

 by glacial deposits. Only an outcrop map with a background of glacial 

 drift could be trusted. 



Now, the fact is that it is the testimony of all workers in this field that 

 the drift is composed almost wholly, if not wholly, of debris of native 

 rock and of rock from areas in the northwest. Agassiz offered no definite 

 lithological evidence of boulders transported northward; Hitchcock can- 

 didly affirmed that the boulders which went southward in obedience to the 

 southeastward movement of the ice-sheet were simply pushed back part 

 way to their sources by the subsequent reverse movement. So far as the 

 Bethlehem moraine is concerned, the only specific piece of evidence of a 

 northward movement is Hitchcock's statement of the occurrence of boul- 

 ders of Franconia breccia near McDonald's, 2 miles north of Eagle Cliff, 

 referred to on an earlier page, as being on the cross-country course of 

 Agassiz's glacier. I visited this locality in 1915, but was unable to find 

 blocks of Franconia breccia there. The McDonald house was long ago 

 abandoned and the farm has become overgrown with woods. Blocks and 

 boulders are conspicuous in a pasture an eighth of a mile west of the 

 site of the McDonald house, but they are of granite gneiss, like the ledges 

 of Garnet Mountain and Mount Agassiz, just north of them. Between 

 McDonald's and the foot of Mount Lafayette, at Eagle Cliff, the country 

 is thoroughly drift-covered and I found no outcrops. Whatever there 

 may be in the drift at McDonald's, it certainly is not safe to assign it to 

 sources in the Franconia Mountains when so much of the region is con- 

 cealed. 



So far as my own observations extend, the boulders on the Bethlehem 

 moraines are either of the native rock — as mapped by Hitchcock — or of 

 rocks which were known by him to occur a short distance northwest of 

 the point of observation. On the northernmost line of moraine, between 

 Apthorp station and the mouth of Barrett Brook (which flows northwest 

 from Bethlehem), angular blocks of foliated biotite gneiss abound — the 

 "Winnepesaukee gneiss" of Hitchcock or a border-zone facies of the 

 "Bethlehem gneiss," as already explained. East of Barretts Brook and as 

 far as Wing Road rounded boulders of coarse porphyritic gneiss pre- 

 dominate, coming apparently from a area mappel by Hitchcock between 

 Manns Hill and Wing Eoad, immediately north of here, where there are 

 some outcrops. The smaller stones in the drift include many of these 

 types, together with iron-rusted "Coos schists" and quartzites and green- 



