88 J. D. Dana on the Quartzite, Limestone, etc., 
Another ridge of quartzite of similar character starts near the 
same point and stretches southeastward, crossing the road from 
Vandeusenville to Alford just west of Long Pond brook. It is 
marked v on the map. No section was found showing the re- 
lation of the Tom Ball slates to the quartzite; but the limestone 
of Long Pond valley, east of the quartzite ridge (at e’) and that 
on the west of it (near e, either side of the road) both dip toward 
the ridge, the latter at an angle o x 0°; and thus it is 
proved that the quartzite is a stratum directly overlying the 
limestone, and, therefore, the same that exists in ridge W. It 
hence follows that the beds of Tom Ball, while all mica slate at 
the north end, are replaced by quartzite in their bottom portion 
at the south end of the ridge. From e, limestone is continuous 
westward and then northward into and through Alford, and 
also southward over Egremont; while from e’ the limestone 
extends eastward to Vandeusenville ; and in this part it is vari- 
ous in its strike and dip. Near g the dip is to the southwest- 
ward, being at the more southern outcrop 35°, with the strike 
N. 50° W.; then, a few rods to the north, 40°, strike N. 35° W. ; 
then 50° to 70°, strike N. 35° to 24° W.; then farther north, 
near the quartzite, 70° to the eastward, strike N. 5° to 10° E. 
This range of outcropping limestone, extending east to Vandeu- 
senville, —- off the quartzite ridge L; or, in other words, the 
quartzite, which is the overlying rock, does not extend across It. 
Along the road opposite the iron furnace, just west of Vandeu- 
senville, the bedding of the limestone is obscure; but the strike 
appears to be east and west and the dip northward 50° to 60°. 
5. I pass now to the fifth of the western sections, or that in 
the line of Great Barrington, two miles south of Vandeusen- 
ville. 
In this section, fig. 7, the limestone on the left (west) is that 
of the Egremont region, already shown to be identical with that 
of Alford, Glendale and Stockbridge. It dips under three hun- 
iF 
Section across the Housatonic valley through Great Barrington. 
dred feet or more of schist (mica schist and gneiss), in which, 
as the section shows, there is a bed of quartzite. The bill 
rises directly from the railroad track at Great Barrington, and 
has the limestone outcropping at its highest part, near z (map); 
as well as along the lower of its western slopes. 
