18 Geology, ^c. of the Connecticut. 



mass will thus be cut up into segments of pseudomorphous 

 crystals. And so it is in the natural specimens: and it 

 seems as though the hand of nature had really made use of 

 a saw in their construction. The plates of mica meet at 

 various angles, yet never cross each other; and the. smallest 

 piece of quartz or felspar is sometimes bisected, so that a 

 part appears on one side of the plate of mica and a part on 

 the other. This rock occurs in the S. Hampton granite j 

 and may frequently be found in other parts of the region 

 extending fifty miles south from Conway. At a little dis- 

 tance the dark bronze coloured mica appears like prisms of 

 some imbedded mineral : and the travelling geologist is of- 

 ten tempted from his carriage in the almost certain expecta- 

 tion of obtaining from this rock shorl or titanium. 



2. Gneiss. 



Coloured Orange. 



Although this is the most abundant rock in New-England, 

 yet the map includes no very extensive portion of it. It 

 stretches over a broad region without the limits of the map 

 on the east and west, especially on the east. On the west it 

 forms a part of the Hoosack or Green Mountains; though a 

 much less part than has been usually supposed. On the east 

 appears with some interruptions of granite, mica slate, Sic. 

 within twenty or thirty miles of the coast, and on the north 

 it spreads over a considerable part of New-Hampshire. 

 The White hills are said to consist chiefly of this rock : 

 though they have not, 1 believe, been thoroughly explored. 



The dip of the layers of gneiss in this rei2;ion varies from 

 20° to 90° — and it dips, like most other stratified rocks along 

 the Connecticut, to the east. When it approaches to horn- 

 blende slate the dip is generally greater than when pure. 

 This rock often contains crystals of hornblende ; in every 

 proportion, indeed, until the characters of gneiss are lost in 

 hornblende slate. Especially is this the case on the east 

 side of Connecticut river. More, however, will be said on 

 this subject when we come to describe hornblende slate. 

 Good examples of this gneiss containing detached crystals and 

 even veins of black hornblende may be seen in the base- 

 ment of the new Collegiate Institution in Amherst. It fur- 



