1880.] NATURAL SCIENCES OF PHlLADELrHIA. 285 



close to the Marble Quariy, but the third is about 400 feet east of 

 these, behiud the barn of Mr. H. S. Hitner, who sa^-s that it Avas 

 found many feet below the surface. These facts indicate an east 

 and west strike to the lignitic strata, and an extent of 400 feet in 

 length and 40 feet in breadth. Shafts 100 feet north of these 

 struck iron ore, but no lignite. They exhibited the following 

 succession of strata: — (1) "Top dirt;" (2) Decomposed hydro- 

 mica slate; (3) White clay; (4) Yellow sand ; (5) Iron ore. 



Recent explorations have shown that Marble Hall is not the 

 only locality where lignite is found, but that it occurs in a number 

 ol other places in the same valley. About a mile and three- 

 quarters west of Marble Hall it was formerly found in a field on 

 the Eidge Road, opposite a house once owned by W. Potts. It 

 was at a depth of about 40 feet. Red and white potters' clay, 

 white kaolin and iron ore are found close to the opening. The 

 lignite at this place is hard, and is said to burn well. Another 

 locality is on the farm of W. Wills, south of Plymouth Creek, 

 about one mile from Conshohocken. Considerable quantities of 

 lignite have been here exhumed, the pieces being often a foot in 

 length. This shaft was opened about thirt}'^ years ago, and was 

 probably the locality referred to by Dr. Leid}'. Lignite has also 

 been found in a number of iron ore pits south of here and east of 

 Conshohocken. It is said always to occur in fire-clay. 



The above localities are all included in a strip of country about two 

 and a-half miles long and a quarter of a mile broad, Ij'ing in nearly an 

 eist and west direction. The lignite appears to form two distinct, 

 na. row lines of outcrop with a definite E. and W. or E. N. E. and 

 W. S. W. strike, — thus conforming with the limestone. While its 

 dip has not been actually established, the decomposed slates and 

 sandstones of apparently similar age have been observed to dip 

 40° S. 20° W. 



From these facts it would appear that the lignite is not a mere 

 local wash or accidental deposit, but thatf it is part of a stratified 

 and distinct formation, having a trend like that of the limestone, 

 and of considerable extent ; and when the strata in the Mont- 

 gomery Count}" Valley are compared with those in other parts of 

 the countr}^, it will be seen that we have here to deal with a forma- 

 tion which, closely connected with the limonite iron ores of the 

 great limestone valleys, and having remarkably similar characters 

 throughout, may prove an important feature in American geology. 



In entering upon a consideration of the age of the lignite, it will 



