E.. Hitchcock on the Coal of Bristol Co., and R. Island. 329 
slates, yet they also show a greater degree of induration, and in 
also more common than usual. These too, are now usually re- 
ferred to the action of heat. The coal, also, from this basin, has 
a greater specific gravity than mest anthracite ; bearing a propor- 
tion to the Pennsylvania anthracite, of 175 to 1°55. It hasa 
tendency greater than usual, to break into cuboidal fragments, and 
t 
tate to pronounce a genuine coal formation. 
Such are the chief circumstances that have so long perplexed 
is a metamorphic coal field. ; 
uch an identification of this deposit is a point of great import- 
ance in forming a judgment of its value, and it therefore seems 
desirable that the evidence should be presented. This will in- 
volve a description of all the important facts with which I have 
come acquainted respecting this coal field. ; 
I. In the first place, the general outline of the surface over this 
corresponds with that of a regular coal field, or basin. tis 
generally nearly level, save some gentle swells and a few outliers 
of rock, the remnants of former more extensive masses. On its 
margin the older and more crystalline rocks rise higher, though 
not very much so; for there is reason to think that both the mar- 
gin and the surface of the coal field have been subject to powerful 
Sxcoxp Serms, Vol. XVI, No. 48.—Nov. 1853. 42 
