2/4 SURFACE GEOLOGY. 



There is an enormous quantity of porphyritic gneiss boulders about tlie village of 

 Northfield, Mass. Until otherwise proved, they may be supposed to have been trans- 

 ported from the area of this ancient gneiss in Winchester by the Connecticut valley 

 glacier. It is also interesting to note the derivation of the Triassic conglomerate. The 

 largest constituent is an oval-shaped piece of granite. Several are two feet long ; the 

 rest are smaller. Twenty-nine specimens represent these pebbles in the museum. They 

 all came originally from the formations to the north-east and north, — none from the 

 west side of the Connecticut. The most abundant are the Montalban schists and gran- 

 ites. Others are the Vernon gneiss, hornblende schist, Coos schists and granites, and 

 several varieties of quartz from veins. 



Boulders of sienite occur at Freedom village, whose origin is unknown. On a high 

 hill in Eaton are boulders of black quartz porphyry, probably from Albany, twelve miles 

 north-west. At the east line of Madison are samples of Albany granite and fine-grained 

 sienite from the same region. At the outlet of Newichwannock lake are black porphy- 

 ries from the Ossipee mountains to the west, presumably. 



In Center Harbor, between Squam and Winnipiseogee lakes, also further south, are 

 many large pebbles of Huronian and Coos rocks. Assuming them to have come down 

 Baker's river, they have travelled 40 miles. With them are i^ieces of the Calciferous 

 mica schist limestone, seen also on Mark's island and in Grafton. These two travelled 

 at least 50 miles. 



At the sea-shore on Cape Elizabeth river are numerous glaciated pebbles of a por- 

 phyry like that of Mt. Pleasant in Bridgeton, or Burnt Meadow mountain in Brown- 

 field, about 40 miles north-west. 



At Littleton, west of the village and near Echo lake, Franconia, are pebbles of anda- 

 lusite mica slate, with acicular crystals, like a rock in Granby and Victory, Vt. The 

 course would have been only a few degrees east of south. 



Handsome porphyritic gneiss occurs on the east line of Effingham. Its source is not 

 clear, whether from the small Albany and Chocorua range, or from the north-east in 

 Maine. The same rock in Haverhill probably travelled west of south from the Wing 

 Road neighborhood. 



A piece of clay slate in Lyndeborough, if from the north-west, travelled 42 miles. 

 Mr. O. E. Randall has shown me pebbles of red sandstones, like that of the Potsdam 

 west of the Green Mountains, picked up in Chesterfield. These are like those men- 

 tioned as occurring commonly about Hanover, page 260, — the distance probably 

 greater — 75 or 80 miles. 



About two miles up Imp brook in Bean's Purchase, almost under the very counte- 

 nance of the Imp, are loose blocks 50 to 60 feet long. Between Mts. Pleasant and 

 Franklin arc many granitic boulders, brought up from the Ammonoosuc valley beneath, 

 10 feet square. Jasper pebbles are common about Connecticut lake and Stewartstown. 

 They probably came from Canada. The same occur upon Mormon hill in the north- 

 east corner of Lyman. There is in the lower part of Hinsdale village a boulder about 

 as large as an old-fashioned school-house, of which the traveller will see many in the 



