28 Geology, ^c. of the Connecticut, 



P. S. Coal Formation. 



Since llie publication of the description of this series of 

 rocks along the Connecticut, I have had an opportunity to 

 examine more extensively than 1 had done before, the coal 

 formation of Rl)ode-Island ; and thus to institute a com- 

 parison between the two. And I feel satisfied that they are 

 very distinct from each other ; and that the Rhode-Island 

 formation is the oldest. There is a sort of general diiFer- 

 ence betwem them, which is readily recognized by the eye, 

 but which it is not easy to describe. Jn the Rhode-Island 

 rocks, however, there is a (i;reater resemblance, in the gene- 

 ral aspect and in the fracture, to primitive rocks than in 

 those of the Connecticut ; and the former are, in general, 

 harder and more compact than the latter; and their cement 

 is more argillaceous. The coarse puddingstone, so abun- 

 dant in Roxbury, Dorchester, &c. and which is seen at in- 

 tervals most of the distance to tlie anthracite beds in Ports- 

 mouth, approaches, in certain varieties, very near a similar 

 ronk in Monta^re, Sunderland. Durham, 4'c. In the first 

 named rock, however, the cement is raiher more abundant, 

 and the rock, as Maclure very happily expresses it, " has 

 the appearance as if the cement at the time of formation 

 had a cons stence sufficient to prevent the particles from 

 touching each other." Certain fine red and coarse gray 

 slates occur in the two formations which can hardly be dis- 

 tinguished, except that those in Rhode Island (as well as 

 most of the other transition rocks there,) are traversed by 

 veins of quartz, but those on the Connecticut never are. 



I would not be understood as endeavouring to prOve that 

 the Rhode-Island formation belongs to tlie Wernerian trans- 

 ition class and that of the Connecticut to the secondary. 

 Both probably are transition ; yet the one may lay claim to 

 a greater age than the other. 



and transition class (of Werner) for ono whicli could lead to an opposite 

 arrano:ement" — ttiat is -with the flcetz class, and also " that the sandstones 

 of the lower partofthis series approach closely in cliai-acter to the more ob- 

 viously mechanical varieties of grey wacke, and indeed so completely pass 

 into that rock, that in many instances tlie limits between this series and 

 thut of transition rocks, can only be arbitrarily assigned." — (pp. 323 and 

 324.) 



