274 GEOLOGY OF OLD HAMPSHIEB COUNTY, MASS. 



Back of Mrs. Haley's, mentioned above, the rock is an obscurely- 

 bedded conglomerate of quartz pebbles in a dark ground containing much 

 slaty ma,terial. The conglomerate here toward its base is exactly like the 

 same rock west of the limestone on the Williams farm, and I have no doubt 

 that they were formerly connected across the valley. Higher up the rock 

 is a pudding-stone, with rounded quartz pebbles up to 4 inches in length, 

 but mostly 1 inch long; the abundant quartz sand and ground which wraps 

 around them cleaves into thick layers coated with muscovite scales and iron 

 rust, so exactly like the upper quartzite of the Williams farm, especially the 

 conglomerate layer, that it is difficult to avoid the conclusion that they are 

 parts of a single stratum. Calculated upon its average dip of 20° the thick- 

 ness of the bed is 400 feet, which is only a rough approximation. 



In the field south of A. Gr. Chapin's house is an interesting outcrop. 

 The rock is here jointed with almost mathematical accuracy into acute 

 rhombs, the joint planes passing through the quartz and quartzite pebbles, 

 and the latter are finely compressed and indented one by another. The 

 rock here carries garnets one-fifth of an inch across. It is unchanged across 

 Dry Brook for a long distance to the northeast, when it crosses the last 

 road; but once over the range, at a point where the brook makes a loop 

 across the road (near J. M. Pickett's), the pebbles are flattened out into 

 thin disks resembling the small lenses of quartz coimnon in crystalline 

 rocks, making it possible that they are of secondary origin — a possibility 

 which does not extend to the range described above. In the woods south- 

 west of this point tlie rock in some beds is in appearance a fine-grained 

 biotite-gneiss, with large garnets surrounded by a broad, annular, white 

 space, in which the biotite is wanting, the iron being concentrated in the 

 garnets. Farther north in the band the i)ebbles grow smaller, and where 

 it crosses the State line it is at base a thin-bedded biotitic quartzite ; 

 higher up, a muscovitic quartzite. In some layers the muscovite becomes 

 abundant and w^raps around pencils of quartz, so that the rock obtains a 

 rude columnar or ligniform structure. It has here an apparent thickness of 

 350 feet. 



At the point already mentioned on the grist mill road (at J. M. 

 Pickett's), where the brook makes a short loop across the road, at the south 

 bridge, is a fine section in a high bluff w^est from the bridge. The con- 

 glomerate strikes N. 45° E. and grades downward thi-ough 50 feet of 



