456 AZOIC BOOKS. 



This variety is found in almost every part of the gneiss, but we would specify the gneiss of Cavendish, upon 

 Section V, as a locality where beds of this variety are particularly numerous. The thick-bedded masses 

 are more common in the gneiss found along Connecticut River. 



IX. HORNBLENDE SCHIST. 



This rock is described separately ; but it must be reckoned as an associated rock, because not only are 

 many of the ranges to be described interstratified with gneiss, but it is very common to find thousands of 

 layers of hornblende schist in all well developed gneiss. There is every variety, from hornblendic gneiss to 

 hornblende schist. The hornblende rock is sometimes deficient in quartz, as in the numerous beds of horn- 

 blende at Mount Holly. It is there nearly pure hornblende, and, on account of its fine grained structure, 

 it is with difficulty distinguished from trap rock. 



X. BEDS OF QUARTZ ROCK. 



Quartz rock is not very common in thick beds, but the number of strata of quartz in the gneiss is legion. 

 They are generally so thin that no notice is taken of them, but they are classed directly as gneiss. We 

 should not pass them by, nevertheless, in the attempt to describe faithfully the characters of the gneiss as a 

 formation. 



XL XII. BEDS OF CALCAREOUS AND MAGNESIAN ROCKS. 



The numerous beds of limestone, dolomite, steatite, and serpentine, need mention at this point only to 

 remind us that they form parts of this formation, although, on account of their theoretical and economical 

 importance, they are described separately. 



XIII. TALCOSE AND CHLORITE SCHISTS. 



It may seem strange that talcose and chlorite schists should be associated with gneiss. They are not 

 very abundant, however. Talcose schist always occurs in connection with the beds of steatite, serpentine, 

 and sometimes dolomite. Both talcose and chlorite schists are interstratified with gneiss at Mount Holly. 



XIV. MICA SCHIST. 



So large a belt of mica schist in the gneiss is found in the towns of Cavendish and Chester, that it is 

 designated as such on the map, distinct from the gneiss. This is one of the best characterized beds of mica 

 schist in the State. It resembles lithologically the nobler varieties of the mica schist of the great calcifer- 

 ous mica schist group. Mica schist is also common in the gneiss elsewhere ; e. g. in Grafton and Athens, 

 near the two beds of steatite. 



XV. EURITE. 



Eurite is an unstratified rock, and is a fine grained aggregate of quartz and feldspar ; no mica is present 

 unless it be in minute invisible flakes. The only locality of this rock we have found in the State is in the 

 northeast part of Londonderry, No. - a in the Cabinet. The gneiss adjoining runs N. 15 E., and dips 60 

 E. The eurite formed a sort of bed three feet wide, whose position is very nearly that of the gneiss. It is 

 very near a large mass of syenite, and veins of epidotic granite and syenite are abundant in the vicinity. 



Other unstratified rocks occur in the gneiss. The trap dikes and overlying masses of trap are the most 

 prominent next to granite. The largest mass of granite is in Stamford. Others are in Sunderland, Ripton, 

 and at Cuttingsville. The largest amount of trap may be seen at Mount Holly and Shrewsbury, along 

 the Rutland and Burlington Railroad. 



