1844.] 417 



both of wliich are impregnated ^vith carbonaceous matter. This 

 plumbaginous rock presents numerous polished surfaces or slicken- 

 sides, on some of which are delicate parallel striae, which reminded 

 me so strongly of the finely striated leaves common in coal, that 

 I had first supposed them to be of the same nature ; and was thus 

 induced to search very diligently, but in vain, for vegetable im- 

 pressions. In the old mine of plumbaginous anthracite about two 

 miles to the north-east of Worcester, the accompanying clay-slate 

 and mica-schist, (the latter containing garnets and veins of asbes- 

 tus), dip towards the north at an angle of between 30 and 40 

 degrees, and a railway cutting east of Worcester, and to the south 

 of the old mine above mentioned, has finely exposed to view the 

 mica-slate and clay-slate with some layers of quartz inclosing a 

 bed of similar plumbaginous anthracite ; some of which has the 

 iridescence of peacock coal. Professor Hitchcock has traced this 

 group of strata in a north-easterly direction 50 miles, to the Mer- 

 rimac river, and the beds are continued with the same strike, in a 

 south-westerly direction, for many miles. In their course they 

 exhibit a great variety of crystalline strata, and the mica-slate 

 sometimes alternates with gneiss. 



The schists including plumbago, at Worcester, as above men- 

 tioned, are separated from the anthracite occurring on the borders 

 of Rhode Island and Massachusetts, by a district of gneiss and 

 hornblende slate about thirty miles wide. The anthracite of those 

 slates is impure and earthy, but has been worked for coal at 

 Wrentham, Cumbei-land, Mansfield, and other places, where, in the 

 accompanying carbonaceous and pyritiferous slates, I collected 

 numerous impressions of the most common coal plants, such asPe- 

 copteris plumosa, Neuropteris Jlexuosa, Sphe7iophyllum, Calamites, 

 &c. This earthy authracitic coal, as well as the accompanying 

 slates, contain pyrites, as at Worcester ; and the anthracite ex- 

 hibits the same glazed surfaces and shckensides ; but it does not 

 soil the finger like that of Worcester, and its specific gravity has 

 been shown by Dr. Jackson and Professor Hitchcock to be less 

 than that of Worcester, but greater than that of the anthracite of 

 Pennsylvania. There are layers and veins of quartz in the slates 

 and micaceous sandstones forming the roof of this anthracite, 

 afibrding another point of analogy between this series and the 

 quartziferous rocks at Worcester. I have also seen numerous 

 specimens from the anthracite and bituminous slate of the neigh- 

 bouring district of Mansfield, in which the usual coal plants were 

 , imbedded ; but the slate was more crystalline. I was presented 

 by Professor Hitchcock with a specimen of distinct mica slate 

 from this neighboui'hood, in which rounded nodules of granite and 

 quartz rock are included ; and in the contiguous parts of Rhode 

 Island a conglomerate belonging to what has been called the grey- 

 wacke formation has been observed by Dr. C. T. Jackson (Survey 

 of Rhode Island, p. 70.) to pass downwards into mica slate. The 

 rocks of the coal measures now under consideration are accom- 

 panied by a red sandstone, which I examined at Attleborough, a 

 few miles from Wrentham before mentioned. There is a con- 



