1880.] NATURAL SCIENCES OF PHILADELPHIA. 281 



has ])een cut througli, and almost encircling it may he seen the 

 thin-bedded Aariet}', with its apparent stratification tangential to 

 the mass from which, by decomposition, it evidently was derived. 

 The true stratification of this bed of gneiss appears to be more 

 nearly horizontal and less contorted than that of any of the rocks 

 of the vicinit)- of Philadelpliia. 



A Neio Locality for Lignite. — Mr. Henry Carvill Lewis 

 announced the discoveiy of lignite, or brown coal, in the lime- 

 stone valley of Montgomery Coanty, a mile and a-half from the 

 boundarj' of Philadelphia. He had found it, last June, at Marble 

 Hall, close to the marble quarry, within a few feet of diggings 

 for iron ore. In order to ascertain its extent and geological posi- 

 tion more definitely, he had caused a shaft to be sunk 40 feet deep 

 on the propertN' of Henry Hitner, Esq. After passing through 38 

 feet of decomposed hydromica slate, there was found a stratum 4 

 feet thick of a tough black fire-clay filled with fragments of lignite. 

 These fragments, sometimes a foot or more in length, lay in all 

 directions in the cla^^ They had the form of twigs and branches, 

 and, though completely turned into lignite, showed distinctly the 

 grain of the wood. The smaller pieces were generally flattened, 

 and offen as soft as charcoal, but the larger ones were quite hard 

 aud brittle and had the shining fracture of true coal. It burned 

 with a bright 3'ellow flame. Frequently l)alls of pyrite occurred 

 with the lignite. 



The clay which contained it was underlaid by sand, and appeared 

 to dip south. It had an east and west strike, like that of the lime 

 stone and of the iron ores. In appearance it was similar to the 

 sub-Cretaceous plastic clays of New Jersey, which also contained 

 lignite I'esembling that of Marble Hall. White kaolin and white 

 and red potters' clay occur in the vicinity and are probably of 

 similar age. They are all older than the surface deposits and 

 gravel of the valley. 



It was stated that while lignite is not uncommon in the Triassic 

 formation, its occurrence in a Silurian limestone valley is of great 

 interest. Whether referred to Tertiary or Jurassic age, it brings a 

 new geological epoch into this region and revolutionizes our ideas 

 of the age of man^' of the so-called *■' Primal " iron ores. 



On Serpentine in Bucks County Mr. Lewis called attention 



to the fact that while serpentine was abundant in Delaware Co., it 

 had not been recorded as occurring anywhere in Bucks Co. He 

 had recently noticed an exposure of it in that county, near the 

 village of Flushing, Bensalem Township. A narrow dyke of hard, 

 impure serpentine here crosses the road near the Neshaminy 

 Creek. He thought that the genesis of serpentine and its relation 

 to the gneissic rocks was still uncertain. 



19 



