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varieties of rock in Andover : 1. Hornblende schist, including syenitic 

 masses apparently intruded after the formation and perhaps meta- 

 morphism of the schist; 2. Gneiss, with similar patches of fine- 

 grained granite ; 3. Very coarse granite ; 4. Fine mica schist. 



The first group is found in the south-east part only of the towns, 

 or south of a line drawn from near J. Farnham's in the Farnham 

 School District to the four corners at the base of Aslebe Hill, thence 

 probably curving below W. Jenkins' saw-mill and running to S. Cheev- 

 er's in the Scotland District, thence to about" the corner at the meet- 

 ing of the towns of Andover, Wilmington, and Beading. Very much 

 of this formation is properly a gneiss, with hornblende in the place of 

 mica. Commonly the divisional planes of stratification and of joints 

 are very even. One of the largest masses of syenite observed occu- 

 pies Aslebe Hill and the territory to the east on the road to Middleton. 

 A mile west of Gray's saw-mill the strata dip 60 N. W. 



The gneiss formation includes an ugly-looking gneiss, a very fer- 

 ruginous variety, quartzites in limited amount, much fine-grained 

 granite, a bed of steatite, and perhaps other varieties worthy of notice. 

 It occupies most of the area of the two towns, lying north-west of the 

 hornblende rock, and limited by an overlying mica schist on the Mer- 

 rimac River. South of Aslebe Hill is a fine-grained granite, not far 

 from the steatite bed at W. Jenkins' saw-mill. The first ledge ob- 

 served west of Aslebe Hill is quartzite. Patches of the fine-grained 

 granite were noted at J. Cummings's, near Carmel Hill ; in small 

 amount at the railroad station at South Andover ; near J. Adams's on 

 . the south shore of North Andover Pond ; several localities south- 

 west from the West Andover Cemetery ; at about three-fourths of a 

 mile north from West Andover church at J. Chandler's, near the Alms- 

 house, and in many other places. There may be a synclinal structure 

 in this formation, for at the South Andover station the dip is 80 W. 

 23 N., and 46 S. E. west of West Andover church. In several other 

 places east of Shawsheen River the north-westerly dip was noticed, 

 and it is my impression that the south-easterly dip prevails in the 

 railroad cut in South Lawrence. Along the north-west boundary of 

 this group there is a belt of peculiar gneiss, whose feldspar has the 

 appearance of small pebbles. I am uncertain whether it belongs to 

 the gneiss below or the mica schist above. 



The coarse granite appears on the map like a flattened ellipse with 

 sharp ends cutting the gneiss at an angle of about 25. I have not 

 searched for it south of Foster's Pond, but to the north from that 

 point, as far as B. Rogers' in the north-east corner of the Phillips Dis- 

 trict, the outcrops are very numerous. From the middle of Scotland 

 District to a point west of Moses Abbott's, nearly a mile and a half, 



