282 



Scientific Geology. 



of Sturbridge — probably the oldest of all rocks — a bed of well charac- 

 terised plumbago. How very probable that all these varieties of car- 

 bon have the same, and that a vegetable origin ? How unphilosoph- 

 ical, when we can thus trace nearly every step of the change, from 

 one variety into another, to call in the aid of other causes to account 

 for the origin of one of them? We see here only the operation of the 

 cause, or causes — whatever they were — by which, as we descend from 

 the newer to the older rocks, they exhibit less and less of a mechanical, 

 and more and more of a chemical arrangement of parts, and fewer and 

 fewer traces of organic remains : until, in the primary rocks, these 

 relics are nearly or quite obliterated. Why should we doubt the op- 

 eration of such causes upon coal, any more than upon other mineral 

 masses ? and if we do grant this, we have an easy and satisfactory ex- 

 planation of the mode in which all the varieties of carbon were pro- 

 duced, except perhaps the diamond: and from the fact that the dia- 

 mond breccia of India is surrounded by, and based upon granite, we 

 may reasonably conjecture that this mineral has been produced from 

 vegetable carbonaceous matter, that has been fused, (for Prof. Silliman 

 has proved that it is fusible) and subsequently crystallized.* And if 

 it be true, that secondary coal is sometimes converted into anthracite 

 and plumbago by the influence of trap, why should we doubt but 

 heat has been the agent of those changes in every case ; especially as 

 it is difficult to conceive how any other agent could have given to 

 rocks and minerals of a mechanical origin, a crystalline or sub-crys- 

 talline structure. 



It will be perceived that I have anticipated some statements in re- 

 spect to the Worcester anthracite and the Sturbridge plumbago. This 

 I have done that I might treat of their origin together, to avoid repe- 

 tition. 



I have said so much in the first part of my report, in respect to the 

 economical uses of the anthracite of our gray wacke formation, that I 

 need add nothing here. I cannot, however, but express my surprise, 

 that the ablest European geological and chemical writers should still 

 represent anthracite as of little or no use, except for furnaces : when, 

 for the last ten or fifteen years, so many thousand tons of this miner- 

 al have been used in our principal cities, along the whole Atlantic 

 coast, in the parlour, the study, and the kitchen ; and so much has 

 been said of its value in our scientific and other periodical journals. 



* Edinburgh Journal of Science, Vol. 10. p. 184. 



