328 E. Hitchcock onthe Coal of Bristol Co.,and R. Island. 
The metamorphic action to which this deposit and the coal — 
have been subject, is two-fold: first, mechanical, secondly, chem- 
tcal 
The mechanical force seems to have operated upon the strata 
containing the coal ina lateral direction, so as not only to raise them 
into a highly inclined position, but also to produce plaits, or folds, 
such as would be formed if several sheets of paper, lying upon one 
another, were taken into a man’s hand, and by pressure on the 
opposite edges, were crumpled so as to form ridges and hollows. 
# * * * * * 
This same effect has been produced upon the coal strata 
of Massachusetts and Rhode Island, as well as in the great 
Appalachian coal field of Pennsylvania and Virginia. e 
miners are familiar with these irregularities, and they constitute 
some of the most serious difficulties with which they meet. in 
the mine of the Blackstone Coal Company, at Valley Falls, R. 1, 
for instance, the bed, and the accompanying rocks, which tor 
a considerable distance dip nearly 45° to the northwest, begin to 
curve so as at length to dip southeasterly. 
In the Aquidneck mine, at the north end of Rhode Island, the 
d of coal that had been worked, was in some places pinched up 
to a width of not more than one or two feet, while in other places 
it has a thickness of from ten to fifteen feet. I noticed here 
have sent veins into the coal strata: a fact that seems to indicate 
that the latter were not deposited till after the granite and syemite 
