62 



OUTLINES OF GEOLOGY. 



baryta, and which yield cobalt, bismuth, copper, and carbo- 

 nate of iron. There are also found irregular deposits of 

 calamine and galena. The bituminous shale of this group 

 contains sulphuret of mercury. 



119. Besides the rocks we have cited, there is a district of 

 France in which the upper and lower beds of marl and sand- 

 stone are separated by a formation of limestone. This is 

 extremely rich in the remains of mollusese, and has in conse- 

 quence been called conchylien. The other rocks of the 

 group are comparatively barren in the indications of organ- 

 ized life, with the exception of the bituminous shale, which 

 often abounds in the impressions of fishes. It has been ge- 

 nerally stated, although incorrectly, that this is the lowest 

 group in which any remains of vertebrated animals are 

 found. The magnesian limestone is the highest rock in 

 which metallic veins are found. 



120. The fossils of this group are characteristic, but are so 

 rare in many of its rocks, that it is often difficult to distin- 

 guish them from an older formation, similar in its mechanical 

 and mineralogical structure. The new red sand-stone of 

 Connecticut exhibits tracks of the feet of gigantic birds. 



121. This formation is among the most extensive in Eu- 

 rope, and is the site of the salt mines of Cheshire and Po- 

 land, and of the mercury of Idria. In this country, it is re- 

 cognized in Connecticut, and is the probable seat of the salt 

 springs and gypsum of the western part of the state of New- 

 York. It seems to be yet undecided whether the very ex- 

 tensive formation of red shale sand-stone and conglomerate 

 which exists in New- Jersey, belong to this, or a more ancient 

 group. IC however, we may form a judgment from the tra- 

 dition of vegetable remains found many years since at Nyack 

 and at Newark, these rocks are of the new red sand-stone. 

 The red marls in New-Jersey contain sulphuret of copper, 

 and copper pyrites, which appear to take their place as 

 stratified rocks, or to be intercalated in the joints. 



