> 
ON STAUROLITE CRYSTALS AND GREEN MOUNTAIN 
GNEISSES OF THE SILURIAN AGE.* 
BY PROF. J. D. DANA. 
In a paper published in the * American Journal of Science” in 
1872 I mentioned the fact, first noticed by Percival, that crystals 
of staurolite are found in Salisbury, Connecticut, in mica schist 
“ underlying” directly the Stockbridge or Canaan limestone. 
Since then I have found in southern Canaan, at a locality in Falls 
Village, west of the Housatonic River (to which I was directed 
by Dr. Stephen Reed of Pittsfield), crystals of this mineral in a 
very similar, well-characterized mica schist; but in this case, the 
schist overlies the limestone and is, therefore, the newer rock.t 
This staurolitic mica schist contains also small garnets. The 
order of superposition is free from all doubt, for the Canaan 
limestone outcrops at the bottom of the same hill, from beneath 
the schist, and the dip is not over fifteen degrees. 
The age of the Stockbridge limestone is admitted by all recent 
writers on the subject to be Lower Silurian. Logan referred it to 
the Quebec group or the formation next below the Chazy. But 
since then Billings has described fossils from the same limestone 
at West Rutland, which he has identified as Chazy. And the 
Crinoids and other species, mentioned in the “Vermont Geological 
Report” as found in the limestone at other Vermont localities 
appear to show, as long since suggested by Professor James Hall, 
that the Trenton limestone is also present in the formations. The 
Chazy and Trenton limestones (Black River included) follow one 
another in New York, and the west and south. That the Canaan 
limestone is the same identical stratum that occurs at Stockbridge 
in Massachusetts, and farther north at Pittsfield, I know from 4 
personal tracing of the rock throughout this region ; and examina- 
tions still farther north in Massachusetts and Connecticut lead me 
to believe in the conclusion of the geologists of the Vermont 
survey, that all is one formation—the Stockbridge limestone, OF 
the Eolian as Hitchcock named it. 
* Read at the Portland Meeting of the Amer. Assoc. Adv. Sci. . 
+From facts I have observed elsewhere, I think it probable the Salisbury schist is 
also an overlying rock. 
(658) 
