260 J. D. Dana on the Quartzite, Limestone, etc., 
(The map, in volume v, may be consulted for the positions of 
these points.) The south end of Beartown Mountain stands on 
i h plateau, 150 feet or more above the level of Muddy 
map), an important geological locality referred to below. 
Three-mile Ridge stands directly opposite, on the west side of 
the valley (as represented in fig. 11).* 
Along the high region from East Mountain near Great Bar- 
rington to Three-mile Ridge on Muddy Brook Valley, the 
rocks, gneiss and quartzite, form a very shallow synclinal. The 
dip at the west end of the section (right end of fig. 10) have 
at first a high dip, or 50°; but it changes in the course of 30 
yards to 40°; and then a mile beyond becomes nearly horizon- 
tal; and in Three-mile Ridge, the low anticlinal which spans 
Muddy Brook Valley is already begun, its rocks dipping 10° 
to 15° to the northwestward. The quartzite at the top of Hast 
Mountain—a stratified and rather soft quartzite, in some places 
gneissoid—disappears to the eastward. In Three-mile Ridge 
to have a thin center of quartzite, and then, in the course of a 
hundred feet, is changed wholly to hard quartzite, while in the 
opposite direction (northward) it retains its mica schist charac- 
ter, but narrows gradually to six inches before passing under 
cover of the soi 
* Muddy Brook has its head just north of this point: but the broad valley con- 
tinues on southward, and becomes the valley of tee Konkapot, and at the same 
time nds eastward, over the lake region of Monterey. 
+ The diagram here given, to be true to nature, should have the dotted line repre- 
senting the meadow land of the valley doubled in length. 
. 
