GEOLOGY OF THE MERRIMACK DISTRICT. 585 



and breaks naturally into prismatic fragments. The same is true of the 

 rocks at South Merrimack, with the addition of fine-grained feldspathic 

 beds. All the rocks in the south part of Merrimack dip to the south- 

 east. 



A few statements will show how these rocks appear farther to the 

 south-west in Massachusetts. In the south part of Lunenburg, along the 

 Fitchburg railroad, is an exposure of a white quartz band, similar to the 

 one mentioned in Londonderry, having the strike N. io° E. A slate near 

 it dips irregularly to the south-east. Crossing from Townsend to Groton, 

 we find, first, gneiss, then mica schist with feldspathic beds dipping 

 45° E. In Shirley, the west part of Groton, and in Pepperell the rock is 

 argillaceous and slaty, dipping east. A mile north of Groton centre is 

 a bed of soapstone, in a jointed mica schist, dipping 25° S. 20°-30° E. 

 Near the north line of Ayer we find the regularly-jointed, coarse-bedded 

 gneiss, dipping 75° N. 20° W. Hence a section here indicates easterly- 

 dipping monoclinal strata resting in a synclinal of gneiss. 



7. Kearsarge Andalusite Group. 



The Monadnock area of andalusite rocks has been described in Chapter 

 V. A similar mass of strata occurs upon Mts. Kearsarge and Ragged, 

 constituting a band twelve miles long and from three to four wide, in the 

 towns of Warner, Sutton, Andover, and Salisbury. Starting from the 

 Warner side, the peculiar rocks of the mountain are first seen at Stanley's, 

 a quarter of a mile south of the toll-gate, standing perpendicular, with the 

 strike N. 30° E. The strata display large contortions, while the gneisses 

 below do not seem to have been greatly disturbed. I have often noticed 

 that the newer strata are usually the ones apparently showing the great- 

 est signs of pressure, but not necessarily crystalline. The older ones 

 may have lost the tokens of a greater action by metamorphism, but it 

 is certainly not apparent in the condition of foldings or faults. For this 

 reason I do not consider it a sure guide to antiquity among our forma- 

 tions, to affirm that the most disturbed are the oldest. Clearly these 

 schists are granitic masses, approximately similar to those so common 

 in the Rockingham country, and they continue until replaced by the fer- 

 ruginous schists at the toll-gate. These occur occasionally in climbing 

 the turnpike. On reaching "Plumbago point" these schists are vertical, 

 VOL. II. 74 



