Jierieu- of flecdit (Trohtificul Llterafii re. '?87 
limestone alternate with the schists, the section in descending order be- 
ing the Greylock schist, the Bellovvspipe limestone, the Berkshire schist, 
the Stockbridge limestone, quartzite conglomerate, and the Stamford 
gneiss. The series has an aggregate thickness of 5,000 feet oi- more. In 
the Hoosac range, a few miles distant on the east, the corresponding 
section has no limestone; and the Greylock series above the conglomer- 
ate is represented there by the Rowe and Hoosac schists. 
Summing up the geologic history of this mountain belt. Prof. Pum- 
pelly writes: ''The results of the survey in northwestern Massachusetts 
lead to the supposition that the central or main ridge was in pre-Cam- 
brian time outlined as a mountain range of highly crystalline rocks on 
the western border of an area of dry land. During long exposure to the 
action of atmospheric agencies and of the products of vegetable decay, 
the rocks of this region had become decomposed at the surface and dis- 
integrated at depths. The breaching action along the advancing shore 
line of the ( 'ambrian sea found ready prepared the materials which the 
water assorted and distributed to form the great sheet of Cambrian rocks. 
While these deposits of detritus were accumulating over the shallow 
areas, the materials for the future limestone were gathering offshore to 
the west. As the positive movement deepened the water shoreward, 
the calcareous materials accumulated above the earlier detrital beds, so 
that we may imagine that, while the later beds of the Cambrian were 
being made of sand and gravel in shallow water, the lower beds of the 
great limestone were being deposited offshore. Later, with a change of 
some kind in the conditions, there came the deposit of finer material 
over the previously shallow region, while the accumulation of limestone, 
with Lower Silurian organisms, still continued offshore. Still later, by 
another change in the conditions, the deposit of finer detrital material 
extended far to seaward, covering everywhere the limestone accumula- 
tions." 
Very thorough structural and petrographic studies of Hoosac moun- 
tain and adjacent territory are presented by Mr. Wolff in pages 35-118, 
plates iv-xi; and of Greylock mountain by Mr. Dale in pages 119-196, 
with plates xii-xxiii. Metamorphism has nearly everywhere produced 
cleavage foliation, which commonly is far more conspicuous than the 
vestiges of the original stratification. On a grand scale the rocks lie in 
a series of meridional folds: and often hand specimens of the schists 
have minute and even microscoi^ic folds and faults. Referring to the 
extreme complexity of these altered and foliated formations, in which 
the sedimentary stratigraphy is usually very obscure. Dr. Woltf re- 
marks: "The gneisses of the Green mountains are just as susceptible to 
stratigraphic investigation as the unaltered sediments of the Appala- 
chians, but the problem is much more difficult owing to the secondary 
structures produced by metamorphism." 
Following his description of the geology of Mt. Greylock, Mr. Dale 
adds a short discussion of the influence of the geologic structure in de- 
termining the present topographic contovu-. 
