GEOLOGICAL SOCIETY. 



13 



Shade mountain, on its southern side, consists of a 

 compact rock, composed of crystalline grains of quartz, 

 and rising to the height of near 750 feet in waving beds 

 and coarse lamina, whose average inclination is about 

 50° S.E. their direction being N.E. nearly. The sur- 

 face of this stone is covered with minute quartz crys- 

 tals, and its masses are every where intercepted by that 

 peculiar striated glance cleavage, so commonly observed 

 in the anthracite coal slates, and even in the coal itself. 

 On breaking this rock, it appears spotted with a brown 

 mineral substance, occupying small cells. This mine- 

 ral oxidates on exposure, and being soon removed, the 

 empty cavities confer a honeycomb appearance on 

 weather-worn masses. Rocks of this structnre are by 

 no means uncommon in the grauwache group. The 

 neighboring parallel ridge of Jack's mountain is of this 

 description on its south side ; and I have even observed 

 fragments on the west side of the Alleghany ridge. 



Red sandstone, (quartose, greywache or grit,) with 

 interlacing white quartz veins, occurs on the, north 

 slope of both the Shade mountain and Jack's mountain, 

 and a similar arrangement prevails in the main ridge of 

 the next group, called the Seven mountains. Coarse, 

 imperfectly defined traces of Fucoides are occasionally 

 seen on the surface of the red sandstones, in all these 

 localities. 



The deposits, which by way of local distinction I 

 have designated as the Fucus beds, comprise strata of 

 different mineralogical character ; consisting of modifi- 

 cations and admixtures of argillaceous, slaty and silice- 



