4 The American Geologist. juiy, isoi 
On these structural principles thirteen complete and six partial 
sections have been constructed across the Greylock mass. These 
show that it consists of a series of more or less open or com- 
pressed synclinals and anticlinals which, beginning at the north 
end ( North Adams ), increase southerly in number and altitude 
with the increasing width and altitude of the schist mass, and then, 
from a point about a mile and a half south of the summit, begin 
to widen out and diminish in number and hight until they finally 
pass into a few broad and low undulations. Mt. Greylock with its 
subordinate ridges is a sj'uclinorium consisting in its broadest por- 
tion of ten or eleven synclinals alternating with as man}^ anti- 
clinals. While the number of these minor synclinals at the surf ace 
is so considerable, in carr3'ing the sections downwards they resolve 
themselves cliiefl}' into two great synclinals with several lateral and 
smaller ones. The larger one forms the central crest of the mass, 
the smaller one east of it forms Ragged ^It. , the subordinate ridge 
on that side. The major central s^'nclinal is so compressed near 
the highest part of the mountain and its axial plane is so inclined 
to the east, i. e. it dips to the west, that the strata which under- 
lie it have on its west side a westerly dip. Further south this 
synclinal opens out and all the relations become more normal. 
On either side of these two main synclinals the subordinate folds 
are more or less open and have their axial planes vertical or in- 
clined east or west. 
The accompanying figure 1, shows one of the more important 
of these cross sections. Section G, which passes about a mile north 
of the top. * That which crosses about a half mile south of the 
top, and through the Bald Mt. spur on the south side of the 
" Hopper," is even more complex in its western portion. 
There are long undulations in the axes of these synclinals as 
shown in several longitudinal sections. The side or edge of this 
great double trough is at the extreme north end of the mass and 
its southern about eight miles distant. South of these main 
troughs is another shallower pair. The same N. S. trough struc- 
ture prevails also through all the subordinate lateral folds. The 
deepest part of the synclinorium appears to be under the saddle 
between the two summits, Greylock and Saddle Ball. 
*In order to show the current conceptions of the topography and 
geology of (Jreylock the reader is referred to Dana's Manual of (Jeology, 
3d edit., 1880, p. 213 where Emmons' section of the mountain is re- 
produced. 
