J. D. Dana—Taconie Rocks and Stratigraphy. 278 
a nearly level pathway through the mountains for the Boston 
and Albany railroad. The tongue-shaped prolongation of the 
limestone area extends eastward through the range, but half a 
mile of schist intervenes between it and the limestone area of 
West Stockbridge and Richmond. 
The southern of the western areas is the only one that makes 
no complete junction with the eastern belt; but it approaches 
it, as explained in the former part of this paper, at the low and 
broad gap in the Taconic range, between Salisbury, Ct., and 
Millerton, N. Y. 
The deep gaps or open valleys that cross the range are deep 
openings through the Taconic schists, and hence the outcrop of 
the limestone through, or nearly through, the gaps. 
These facts touch a fundamental point in the Taconic sys- 
tem, for they show that the difference in grade of the meta- 
morphism between the limestone areas of the eastern and 
western sides of the 'Taconi int of difference dwelt 
upon by Emmons—has no stratigraphical importance. The 
rocks are one in mass beyond possible question. We thus 
take one member out of the Taconic system by showing its 
continuity with one of the others. We find, in other words, 
that the great limestone of the Taconic series is stratigraphically 
one single formation. This statement does not imply that the 
limestone is all of one period; but that it is one in mass and 
general conformability. 
This conclusion is fortified by the ane already presented of 
a synclinal structure in Mt. Washington, that is, of the passing 
of the limestone from east to west underneath the mountain ; 
and also by that of another synclinal, as long since pointed out 
by Emmons, and also afterward by Hitchcock, in the Grey- 
lock mass, by which the Williamstown and Adams limestones 
—the Holian-and Stockbridge—join one another. Additional 
evidence on the latter and related points will be found beyond. 
4. Irregularities in the courses of the belts of the Taconic series 
that appear to be, in part at least, due to earlier topographical con- 
ditions.—Two abrupt ‘east-and-west shifts in the course of the 
Taconic belt are indicated on the map. 
a. The most extensive of these abrupt changes of line is in 
the northern part of Berkshire. Here the eastern or Stock- 
bridge limestone, as above stated, stops off abruptly in the town 
of Clarksburgh, and begins again to the westward in Williams- 
town. This “change in geographical position amounts to four 
or four and a half miles, measuring from the eastera limits of 
the two limestone areas. 
The quartzyte is shifted to the same extent. Too the south, 
through Cheshire, East Lenox and beyond, the line of 
quartzyte outcrops is in general four to five miles east of the 
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