J. D. Dana—Taconic Rocks and Stratigraphy. 398 
Art, XLIII—On Taconic Rocks and Stratigraphy, with a Geo- 
logical Map of the Taconic region (Plate XI); by James D. 
DANA. ) 
Part II. The Middle and Northern Part. 
(Continued from p. 276 of this volume.) 
THE map of Middle and Northern Berkshire mentioned in 
the preceding part of this paper (p. 270 of this volume), is here- 
with published. For detailed explanations of the symbols and 
letters used on the map, the reader is referred to p. 206 of vol- 
ume xxix (March, 1885) of this Journal.* The map illus- 
trates fully the points presented on pages 271-276: (1) the. 
eastern limestone with its intercalated and often isolated ridges 
of schist; (2) the passage of the eastern limestone belts into the 
western—as that of the Vermont through North Bennington, 
into the Hoosac and Petersburg area, that of the Vermont, 
through Williamstown and Hancock, into the Lebanon and 
Canaan area, and the near approach of the latter at Canaan to 
junction with the Stockbridge limestone in West Stockbridge; 
(8) the variations from normal directions and continuity in the 
belts, apparentiy due, for the most part at least, to earlier topo- 
graphical conditions—exemplified (1) in the Williamstown and 
Clarksburg region; (2) in the town of Bennington; (8) in the 
* For the convenience of the reader, the following explanations of the lettering 
on the map and the symbols in the figures beyond, are here repeated in brief. 
Q, quartzyte; M, mica schist; M, (not used before) hvdromica schist; Gn, gneiss; 
A, Archean. In the figures, a dot stands for quartz, a hyphen for mica, and a 
cross (+) for feldspar, a long hyphen — for hydrous mica; dots for quartzyte ; 
alternating dots and hyphens - - - - for mica schist; alternating dots aud long 
hyphens - — - — for hydromica schists; and alternating dots, hyphens and crosses 
(- - +) for gneiss; alternation of four dots with a hyphen (-------- -) for 
micaceous quartzyte ; alternations of two or three dots with a hyphen (- - - - - -) 
for quartzytic mica schist; the lines alternate with a rule, for a bedded or schistose 
rock as mica schist, hydromica schist and bedded quartzyte; and groups of 3 or 4 
lines with rule between, for gneiss or slightly bedded quartzyte. In the section 
_the dip of the lines is the true dip; an unfilled space in the inner part of a figure 
of a section signifies that the dip was obtained from exposures over the surface, 
and not from an actual transverse section; while an unfilled interval between the 
lines indicates a concealment by soil, and the figures added, the width of the coy- 
ered surface; the end of a figure to the right is always the eastern or northern 
end; a circle with a letter inside means a quarry or ore-bed, and the letter indi- 
cates the material afforded: Fe, the iron-ore, limonite; Q, quartzyte as hearth- 
stone or sand. The map was plotted on the maps of Beers’s Atlases, which, 
while of great value for the purpose, have not the accuracy of a thorough survey 
of the region; and hence some unavoidable errors are introduced which I could 
easily make right on a new map of equal size (mostly two inches to the mile), and 
having all of its details, including the positions and names of owners of all houses 
which aid in marking localities or as a base for measurements. Some of: the 
areas, as the narrow one of schist in New Alford, might take a more probable 
form on such a map, since the roads have been the chief means of fixing the 
courses of the outlines. As in the map of Southern Berkshire, it was not possible 
to adjust to the Massachusetts map the lines on the portion of Connecticut added 
to it, so it is as regards the addition of Vermont. Scale 4 inch=} mile. 
