PHYSICAL HISTORY OF NEW HAMPSHIRE. 537 



easterly. Afterwards the land sank, and these chasms were filled up 

 with mud, which eventually became converted into Cambrian slates. 



Not far from the same epoch long bands of clay slate were deposited 

 in the Connecticut valley, extending from the Massachusetts line to Coos 

 county. In some parts of this formation large veins of auriferous quartz 

 were formed, whose metallic contents were derived from the Huronian 

 strata, and more effectually concentrated than before. Many of the 

 veins afford evidence of having been deposited from hot water. The 

 layers of accretion are easily distinguishable. The gold may have been 

 reduced from solution by the same process as that recently described. 

 These auriferous deposits are of sufficient richness to be worked to 

 advantage. 



The Coos ocean occupied very much the same position as the Huro- 

 nian. Along the Connecticut valley it covered the greater part of 

 eastern Vermont, in Orleans, Essex, Caledonia, and Orange counties. 



The Waterford-Reading ridge did not separate the waters of the 

 Connecticut valley from those just mentioned farther west. The Ver- 

 mont part of the deposit is mostly calcareous. A few scanty remains of 

 crinoidal stems have been taken from this rock in Derby, Vt., showing 

 that life existed. Bordering Connecticut river in New Hampshire, from 

 Haverhill to Hinsdale, the Coos rocks are composed chiefly of quartzite, 

 mica schist, and slates full of crystals of staurolite and garnet. This 

 deposit therefore consisted originally of clays of various composition. 

 Overlying the Atlantic gneisses, between Landaff and Keene, is an 

 extensive deposit of andalusite mica schist, including Mts. Carr and 

 Moosilauke. Mt. Monadnock is an isolated mass of the same rock, as 

 is also the Kearsarge-Ragged area. These schists have but recently 

 been distinguished from the adjacent rocks, and may be the equivalents 

 of the Coos group. If formed at the same time, the depositing ocean 

 may have been separated from the Connecticut valley by an Atlantic 

 ridge. The strata correspond in thickness very well with that of the 

 staurolite rocks. 



The Connecticut Coos period can easily be divided into three parts, — 

 first, the epoch of the deposition of mountain masses of silica ; second, 

 of hornblende and mica schists ; third, of limestone. 



The enormous veins of copper and iron pyrites in Strafford and 

 VOL. I. 70 



