GEOLOGY OF THE CONNECTICUT VALLEY DISTRICT. 393 



tion from the CoiJs schists may enable us in the future readily to assign 

 them where they belong. As a rule, the Coos slates differ from the Cam- 

 brian by the occasional presence of staurolite and garnet; by standing at 

 smaller angles, the latter being very commonly vertical; and by the ab- 

 sence of auriferous quartz veins. The first area of this kind in the Con- 

 necticut valley has already been described in Lisbon (p. 318). Next are 

 two small areas in Piermont. Two others in Orford have been alluded 

 to, upon page 383, where reference is made to the existence of cleavage 

 planes distinct from the stratification. The largest one known begins 

 south of Acorn hill in Lyme, and extends through Hanover and East 

 Lebanon, being almost the continuation of the Cambrian range from 

 Springfield, Vt., to Plainfield. This is crossed by sections in Figs. 54, 

 55' 56' 58, ^nd 60. The smaller areas are all readily referred to the syn- 

 clinal form, and are believed to be small fragments of a newer scries than 

 the adjoining schists. This larger area is not so easily disposed of. It 

 is easy to call its position on the Lyme section (Fig. 54) an anticlinal. 

 Figs, 55 and 56 show a still better correspondence with the basin struc- 

 ture. We have more abundant information concerning the region of Fig. 

 58, along the valley of Mink brook and over Hayes hill in East Hanover. 

 Passing up Mink brook, we find the gneissic series extending as far as 

 the first crossing by the road above the Baptist church. The slates suc- 

 ceeding at the second crossing dip 75° and 60° W., the latter in the road 

 turning northerly. A few rods higher up, at a small fall, the slates dip 

 80° W. There and farther along are frequent layers of a slaty conglom- 

 erate. This must be newer than the ordinary slates, since it is composed 

 of the ruins of an older series. I have sometimes surmised them to be 

 as recent as the Helderberg, an impression heightened by the occasional 

 occurrence of patches superficially resembling corals. At an old mill- 

 site, at the upper end of a sort of gorge cutting through the glacial drift, 

 we find similar slates, with conglomerates, standing vertically. There 

 are bluish quartzites interstratified with the slates at the brook crossing 

 above the gorge, also vertical. The slates at a road turning northerly to 

 a school-house, up a large tributary, are slightly plumbaginous and soft. 

 A quarter of a mile beyond, after passing several slate outcrops without 

 essential change of position, an interesting dyke of dolerite cuts the 

 slate at a slight angle. This trap is remarkable for containing perfect 

 VOL. II. 50 



