1880.] NATURAL SCIENCES OF PHILADELPHIA. 283 



paper by Prof. Lesle3\^ Here again it was found in a limestone 

 valley close to iron ore excavations. It was at a depth of 40 feet, 

 belo-sv strata of clay and sand. According to the superintendent 

 of the mine, it was in two strata, the lowest of which was 18 

 feet in thickness, and was separated from the upper bed, 4 feet thick, 

 b}^ a stratum of sand. Below it, at a depth of 65 feet, red and 

 white plastic clay occurred. The strata were nearly horizontal. 

 It was thought that the lignite was not necessarily connected with 

 the iron ores, but w^as a local deposit of late date, made in a shallow 

 pond, and that, as at Brandon, a sink-hole had been formed in tiie 

 underlying limestone. It was regarded as of the latest Tertiary 

 age. 



Lignite has also recentlj^ been discovered by Prof Prime, in 

 Browm's iron mine, at Ironton, Lehigh Co., Pa.- He states that 

 it occurs in a Avhite plastic clay, but does not give the depth at 

 which it was fonud. He believes that it was transported by ice 

 and water in the Glacial epoch, and refers the iron oz'es of the 

 valley- to the same origin. 



The writer believes that in the light of facts now developed, 

 this theory of the age of the lignite cannot be maintained. After 

 an inspection of the locality, he has found that the surface-drift 

 and boulders of that valley lie unconformably upon the forma- 

 tion containing the lignite. The lignite lies at a depth of 46 

 feet from the surface, in a tough plastic clay, which is entirely 

 free from boulders. About 30 feet of potters' clay and decom- 

 posed hydromica slate lie upon the lignitic stratum, and resting 

 upon the whole is 15 feet of drift. This surface drift, of yellow 

 brick-clay, boulders, gravel and drift iron ore, is thus of quite 

 different character from the strata below it, and is probably de- 

 posited b}^ glacial water's. The underlying formations have, 

 apparently, in some places, a dip like that of the adjacent lime- 

 stone, and are certainly more ancient than the surface drift. 



The lignite recently found by the writer in the Montgomery Co. 

 valley, and described at the last meeting of the Section, occurs 

 under conditions very similar to those above indicated. In im- 

 mediate proximity both to a limestone outcrop and to iron ore 

 diggings, it was found at a depth of 35 feet, in a plastic cla}'- 

 which contains no gravel or boulders, and which is overlaid by 



1 Proc. Amer. Phil. Soc, ix, 463. 



^ Report DD., 2d Geolog. Survey of Pa., p. 76. 



