378 



- Scientific Geology. 



here to be remarked, that in many other places in the broad gneiss 

 range of Worcester county, the rock takes so much hornblende into 

 its composition, that it properly becomes hornblende slate. Some of 

 these beds — as in Pelham — bear a closer resemblance to unstratified 

 secondary greenstone than any other member of the primary rocks : 

 (No. llll.) and I have accordingly placed specimens from them 

 among those of greenstone. 



The deposit of this rock in the west part of Northfield, north part 

 of Gill, and east part of Bernardston, is represented as in contact 

 with mica slate, quartz rock, and new red sandstone: and such I be- 

 lieve to be its associations ; though recent examination has led me 

 to suspect that gneiss alternates with the mica slate. The hornblende 

 slate of this region is sometimes slaty ; but very frequently it is de- 

 cided primitive greenstone, exhibiting even sometimes a passage into 

 sienite. In some parts of the bed no marks of stratification, or slaty 

 structure, appear : but they are almost uniformly present in other 

 parts. In one instance, at least, a vein of white fetid quartz, nearly a 

 foot wide, traverses this rock. This spot is on the road from Gill to 

 Bernardston. The quartz near the edges of the vein contains foli- 

 ated masses of feldspar. 



Four other deposits of hornblende slate are represented on the 

 map, surrounded by mica slate, in the western part of Franklin 

 county. I have recently ascertained hat the deposit, which extends 

 from Colrain to Conway, is associated with a limited stratum of 

 gneiss, whose characters are fully developed in the east part of 

 Buckland. The hornblende slate lies principally in the west part of 

 Shelburne, occupying a high hill. 



In respect to the other three patches alluded to above, I have no 

 remarks to make, except to say that I do not suppose I have very ac- 

 curately marked out their true limits, or situation. I know that in 

 the vicinity of the spots where they are marked, I have repeatedly 

 found hornblende slate. But I also know, that nearly all analogical 

 reasonings as to the situation of this rock have failed me. 



About one mile north of Whately meeting house, we find a lim- 

 ited deposit of hornblende slate, on the west side of the street, prob- 

 ably succeeding the red sandstone. Passing westerly not more than 

 100 rods, we cross almost every variety of this rock, that has been 

 named : the common hornblende slate, which predominates : also 

 that containing epidote, w r hich is frequently divided into rhomboidal 

 masses of considerable regularity : then we come to primitive green- 



