Geology, &c. of the Connecticut. 21 
posed to regard this rock as gneiss containing an accidental 
proportion of hornblende; and this would have been a satis- 
actory description of a considerable part of the rock which 
I have called hornblende slate. But another part appears 
to be decidedly that species of Werner’s primitive trap de- 
scribed under the name of hornblende slate in Rees Cyclo- 
pedia, Article Trap—that is, it consists of bdveblesdes gen- 
erally fibrous and crystalline, having a very distinctly siaty- 
structure. For localities of this well characterized horn- 
blende slate I would mention the eastern part of Halifax, 
Vermont, also New Fane and Belchertown, two miles north 
of the meeting house on the west side of the road, and in 
the ware part of Tolland and Monson. 
owever that the largest part of this rock will be 
found “ consist of hornblende, quartz and mica—the latter 
beiog usually black and very apt to be confounded with the 
rnblende, so that perhaps it deserves the name of a granitic 
aaveane In some instances, also, this rock contains chio- 
rite, and verges towards greenstone slate. It is often 
ee intermixed, and alternates with gneiss and mica 
slat 
Anas portion of this rock has a porphyritic aspect. 
I use the term porphyritic in this place, not in the usual 
tals, but as a “granite ground, in which some crystals are 
much larger than the rest.” (Bukewell’s Geology, p. 28.) 
The slaty structure of the rock, though less distinct, is not 
lost: but the imbedded fragments, or imperfect crystals of 
quartz or felspar, most frequently the former, give it a 
porphyritic appearance. These imbedded fragments are 
frequently granular, while. the base is distinctly crystalli- 
zed. A good example of this a of rocks occurs in the 
west part of Chatham and in Shelburne. Sometimes this 
Hawley, a few rods west of the meeting-house, and at the 
falls in Deerfield river in Shelburne. 
These porphyritie rocks. however, must be quite different 
from any thing occurring in Europe by this name, if a re~ 
mark of Brongniart be correct, that “we are not at present 
able to find a sienite or porphyry which is evidently primi- 
tive.” For we have as much evidence of the primitive char- 
