284 



PROCEEDINGS OF THE ACADEMY OF 



[1880. 



clay and decomposed hydromica slate. A surface drift, containing 

 iron ore, gravel, and occasional boulders, lies unconformably upon 

 the whole formation. The section here presented was made in a 

 shaft which the writer was allowed to have sunk within a few feet 

 of Mr. Hitner's marble quarry, Marble Hall, Montgomery County. 



FEET. 



10 



m 



2^ 



LLLLU 



" Top dirt," yellow, impure. 



Soft white decomposed hydromica slate or im- 

 pure " kaolin," containing occasional broken 

 seams of sharp quartzite,'but no pebbles. 



Coarse white sand and rounded pebbles ; appar- 

 ently a decomposed sandstone. 

 Tough mottled red claj'. 



Blue plastic clay. 



Lignite in a very tough, dark clay. 



Coarse yellow sand, with fragments of stony 

 iron ore and with pebbles. 



The lignite bed contains occasional streaks of fine gray sand, 

 and is underlaid by a coarser sand. So far as could be judged 

 from the very limited exposure, it dipped south, at an angle of 

 about 30° ; becoming thicker as it dipped. The lignite lies in 

 fragments in the clay, and consists of twigs and branches of land 

 plants, apparently all dicotyledonous. The lignite frequently 

 shows a brilliant black lustre when transversely fractured. The 

 small fragments are more like charcoal, and are often in the form 

 of flattened twigs. Some of these appear to be partially rounded 

 by attrition. No shells or marine fossils occur. Pyrite frequently 

 encrusts the lignite or forms nodules, and when exposed to the 

 air decomposes into ferrous sulphate. 



At this same locality, lignite has been taken from three other 

 shafts in addition to the one just described. Two of these are 



