264 J, D. Dana—Geology of Vermont and Berkshire. 
compound synclinal, and to this owe the apparently great thick- 
ness of its andalusitic mica schists. Flexures of less span than 
five miles, and. much less, are far more common among steeply 
dipping rocks than those of greater extent, and sisnply because, 
under the pressure producing such bold upturnings shaly strata 
cannot help flexing at narrow intervals, so as to have frequent 
local flexures subordinate to the larger folds. 
twenty miles. 
he magnitude of the results are strong evidence that the 
so-called limestone-area is really but a small part of a larger 
region of cotemporaneous disturbance and uplift. The true 
e 
Valley on the west, and so had the breadth of the Appalachian 
disturbance of a later epoch, or whether it had narrower limits 
—may be ascertained by studying the stratification. Some o 
the results of such a study as regards Connecticut and a 
portion of New York I propose to give in another paper. 
are needed for a conclusion. 
