Geology, S/c. of the Connecticut. 20 



ers. I shall confine my remarks principally to that range 

 extending from VVhately to Northampton, because I have 

 examined this most. 



As above remarked, this range appears to be mostly a si- 

 enitic granite, that is, a modification of granite; and very 

 different from that sienite which is associated with gray- 

 wacke and greenstone. A person coming from the west or 

 north-west towards the village of Northampton, will pass 

 over the most decided granite, associated with mica slate, 

 till he comes within four or five miles of that place. He 

 will then find the texture of the rock to be finer, and in some 

 ijpstances it contains a portion of hornblende, while the pro- 

 portion of quartz is somewhat diminished, the felspar 

 frequently becomes red. Veins of graphic and common 

 granite, epidote. Sic. are more numerous, and the rock ap- 

 pears more disintegrated than the coarse grained granite. 

 In one part of a mass of this rock, may frequently be ob- 

 served a considerable proportion of hornblende, thus giving 

 the rock a sienitic aspect, while in another part, only a few 

 feet distant, this mineral is wholly wanting. Coming near- 

 er Northampton, however, we find the hornblende more 

 and more abundant, until we arrive at the eastern edge of 

 the range, where we find a rock containinglittle else than fel- 

 spar and hornblende,forming a real sienite. I have never yet 

 seen a specimen, however, in which careful inspection could 

 not discover both mica and quartz. The felspar is usually 

 deep flesh colored, and the hornblende sometimes black 

 and sometimes green. On the eastern border of this range, 

 especially about two miles north of the village of Northamp- 

 ton, on the west side of the stage road, this sienite assumes 

 a trappose and somewhat columnar form, both among the 

 loose masses and those in place.* Among the debris, the 

 three sided pyramidal form is most frequent; sometimes we 

 find a three sided prism, and sometimes, both among the 

 loose masses and those in place, two, three or four faces of a 

 prism of a greater number of sides. 



Another spot for observing some interesting facts in re- 

 gard to this rock, is the south part of Whately. Two miles 

 south of the congregational meeting-house, on the road to 



*This fact was first mentioned to mo by that indefatigable and able natu- 

 ralist, Mr. Thomas Niittall. 



