264 



GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



rock is clark-gTa)- quartzite, at times a cong-lomerate, weatherinu: very rough, 

 with strike and dip very irreguhir and uncertain, with many sHght slips 

 and crushings — indeed, often completely brecciated and recemented with 

 limpid quartz. Locally it passes into a black siliceous slate by the micro- 

 scopical development of biotite and the accumulations of coaly matter. A 



Fig. 16. — Section of Devonian rocks from tlie "Williams farmhoase 250 rods northwest to tlie sharp bend in the road 

 over West Mountain, along the section line on map, fig. 15. 



few scales of the former mineral can be seen with the lens. Up the hillside 

 from the limestone along- the line of dip, two small ledges of the rock appear, 

 as may be seen from the section, widely sejDarated from each other and from 

 the rocks above and below. 



It is not difficult to find among tlie less crushed portions of each ledge 



/c^rfu hr c/xiiV conform ty befiveen I /nesfon^^nd OLiarfT fe 



Fig. 17. — Section of the "Williams farm quarry ; an enlargement of the center of fig. 16, at a of fig. 15. 



pieces which agi'ee exactly with the quartzite above the limestone, especially 

 that which outcroj^s a few meters above the latter, and its peculiar appear- 

 ance is largely due to crushing and infiltration of quartz. The same result 



