38 DESCai?TIONS 



11. METALLtPERous Ltmerock, consists of carbonate of 

 lime in a homogeneous state, or in the state of petrifactions. 

 Subdivisions. Compact^ when it contains but few petrifac- 

 tions and is susceptible of a pohsh. Shelly, when it consists 

 of petrifactions, mostly of bivalve molluscous animals. Varie- 

 ty. Birdseye marble, when the natural layers are pierced 

 transversely with cylindric petrifactions, so as to give the 

 birdseye appearance when polished. The true metalliferous 

 limerock is always compact, as far as I have examined. But 

 Carbonifer- vock Called the carhoiiiferous limestone by Europeans, has, 

 stone and' equivalent in this country, a covering of limestone, 



cherty lime- and, in some localities, it has a higher covering of cherty 



stone. . ' . .. S J 



limestone ; that is, limestone containing hornstone. An ex- 

 ample may be found by tracing Catskill Creek from its mouth, 

 about four miles. But it is separated by interposed carbo- 

 niferous and quartzose rocks, where it passes through Albany 

 county. 



Localities. Compact, on East Canada Creek, Otsquaga 

 Creek, and west of Little Falls. Shelly, Trenton Falls, 

 north of Utica, Glen's Falls, twenty miles north of Saratoga 

 Springs. Variety. Birdseye marble, is the compact, to which, 

 when polished, the vertical encrinites give a birdseye appear- 

 ance. All these kinds, terminating upwards in the cherty kind, 

 may be traced from Catskill, by way of the Delaware and 

 Hudson Canal, until they may be seen passing laterally under 

 the carboniferous slate, which embraces the Carbondaie and 

 other coal beds along the Susquehanna, in Pennsylvania. 



Class III. Lower Secondary, or Third Series. 

 3. Carbo- 12. Second Graywacke, is an aggregate of grains of 

 mation^ quartzose sand, less angular than those of first graywacke, 

 and generally contain some fine grains of limestone. It can 

 scarcely be distinguished from first graywacke in hand speci- 

 mens ; but it is always above calciferous sand rock and me- 

 talliferous lime rock. Subdivisions. Graywacke slate when 



