GLACIAL DRIFT. 259 



from deposition, as there has been no sorting of the material. Possibly 

 some authors have mistaken these lines for stratification. 



An uncommon feature is the presence of cracks and cavities, or what 

 seem like such openings, one or two inches wide, filled with the upper 

 gravel. Some masses of the lower till are entirely encompassed by 

 them, so that in a section they appear like imbedded, irregular patches. 

 The till occupies most of the area, the gravel occurring mainly in the 

 veins. The section suggests the possibility of ice occupying the present 

 position of the veins at first, and the subsequent infiltration of gravel 

 after the melting of the frozen material. There are cases on record of 

 large fragments of boulder clay transported by ice as if they were rocks_ 

 There might have been disturbances in the till, and the interspaces sub- 

 sequently filled with gravel. This gravel does not show any cleavage 

 structure like that of the lower till. 



The larger of the boulders here are of granite, such as occurs within 

 two miles. Those next in size are of the Manchester or Hooksett quartz, 

 and mica schists of Andover and Franklin. Stones four inches long are 

 composed of the Albany granite, and there are also two kinds of White 

 Mountain porphyry. Similar White Mountain boulders occur in a rail- 

 road cut very near Massabesic lake, in a compact, elongated moraine, 

 different from anything else in the vicinity. 



The greatest distance of carriage indicated by these boulders is 68 

 miles. The mica schists travelled about 35 miles. The great bulk of 

 the stones on Wilson's hill has come, therefore, from 35 miles and less. 



A pebble of White Mountain porphyry has been shown to me by a 

 resident of Nashua, who found it near his home. This must have 

 travelled as much as 86 miles. 



Concord. 



An examination of the Concord kame showed many stones 8 to lo and 

 12 inches in diameter, more than three fourths consisting of the Con- 

 cord granite and associated rocks. I found, also, white quartz, ferrugi- 

 nous schists, porphyritic gneiss, trap, blue quartzite, hornblende schist, 

 gneiss, and a possible example of Huronian schist from the Connecticut 

 valley. Careful search failed to discover any rocks from the White 

 Mountains. This indicates that the locality is too far west to receive 



