336 Scientific Geology. 



placed in the transition formation. It seems almost certain that no 

 primitive anthracite exists."* I asserted in the first part of my Re- 

 port that some of the anthracite in this country, viz. that at Worces- 

 ter, occurs in primitive rocks, because it exists in mica slate. A re- 

 viewer says that " he has certainly spoken unadvisedly when he as- 

 serts that it is so found in this country."! But had he been aware 

 that I reject the transition class, and consequently, following Maccul- 

 loch, include every variety of mica slate and gneiss, the older varie- 

 ties of quartz rock, and clay slate, in the primitive class, he would 

 have seen that my statement was in perfect accordance with the au- 

 thorities quoted above ; and their correctness and high standing, 1 

 presume, he would not call in question. When Prevost asserts that 

 " no primitive anthracite exists," he means none which he calls prim- 

 itive. But in the same paragraph he says that this mineral does ex- 

 ist in mica slate and gneiss ; every variety of which, geologists of no 

 mean name regard as primitive. If this is all that is meant by the 

 reviewer, there is between him and me no difference of opinion, ex- 

 cept in the use of the word primitive. 



If it be true, as I suppose, that the Worcester anthracite occurs in 

 mica slate, we see the reason why it approaches so nearly to plumba- 

 go, as I have elsewhere shown that it does. For whatever be the 

 cause, as a general fact it is true, that the older the rock in which car- 

 bon is found, the more compact it is, and the nearer does it approxi- 

 mate to the semi-crystallized condition of plumbago. 



On the first edition of the map a small patch of mica slate was rep- 

 resented in Sherburne. But its extent, as I observed it, was so limited 

 that I have thought it best to omit it. I am not without suspicion, 

 however, that this rock may be found of considerable extent, con- 

 nected with granite, in Sherburne and in the towns north of that 

 place, as far as Sudbury at least. 



The narrow strip of mica slate in Smithfield. R. I. represented on 

 the map as associated with talcose slate, is of rather a peculiar char- 

 acter. It is decidedly arenaceous, and even resembles certain mica- 

 ceous sandstones. (No. 675.) 



The tongue of mica slate exhibited on the map, as extending 

 through the east part of Andover into Middleton, is very probably 

 connected with the Worcester range ; since the direction and dip of 



* Diet. D'Hist. Nat. Art. Houille. 



t Peter A. Browne, Esq. Bucks County Intelligencer, Sept. 3, 1832. 



