728 HISTORICAL GEOLOGY. 



Lower Silurian. 



I. Potsdam. — "Primal Series" of Rogers: sandstones and slates, 3000'-4000'. 

 IL Calciferous. — " Auroral" calcareous sandstone, 250'. 



Chazy. — "Auroral " magnesian limestone, with some cherty beds, 5400'. 

 Trenton. — "Matinal" limestone, with blue shale, 550'. 



III. Utica. — " Matinal " bituminous shale, 400'. 



Hudson. — "Matinal" blue shale and slate, with some thin gray calcareous sand- 

 stones, 1200'. 



Upper Silurian. 



IV. Oneida. — " Levant Gray " sandstone and conglomerate, 700'. 



Medina. — "Levant Red" sandstone and shale, 1050'; and "Levant White'* 

 sandstone, with olive and green shales, 760' : total, 1810'. 

 v. Clinton. — " Surgent Series," shales of various colors, both argillaceous and cal- 

 careous, with some limestones, ferruginous sandstones, and iron-ore beds, 2600'. 

 Niagara. — Not well defined ; possibly corresponds with part of the " Surgent 



Series." 

 Salina. — "Scalent" variegated marls and shales, some layers of argillaceous 

 limestone, 1650'. 

 VI. Lower Helderberg. — ' ' Scalent ' ' limestone, thin-bedded, with much chert, 350' ; 



" Pre-meridian " encrinal and coralline limestone, 250' : total, 600'. 

 VII. Oriskany. — " Meridian" calcareous shales, and calcareous and argillaceous sand- 

 stone, 520'. 



Devonian. 



VIII. Upper Helderberg, Cauda-galli. — "Post-meridian" silico-calcareous shales, 200' to 

 300'. 



Corniferous. — "Post-meridian" massive blue limestone, 80'. 



Marcellus. — " Cadent " Lower black and ash-colored slate, with some argilla- 

 ceous limestone, 800'. 



Hamilton. — " Cadent" argillaceous and calcareous shales and sandstone, HOC 



Genesee, — " Cadent " Upper black calcareous slate, 700'. 



Portage. — " Vergent" dark-gray, flaggy sandstones, with some blue shale, 1700'. 



Chemung. — "Vergent" gray, red, and olive shales, with gray and red sand- 

 stones, 3200'. 

 IX. Catskill. — " Ponent " red sandstone and shale, with some conglomerate, 6000'. 



Carboniferous. 



X. Pocono. — "Vespertine" coarse, gray sandstones and siliceous .conglomerate at 

 the eastward, becoming fine sandstones and shales at the westward, 2660'. 

 XI. Mauch Chunk. — "Umbral" fine red sandstones and shales, with some limestone, 



3000'. 

 XII. Millstone- grit, or Pottsville conglomerate. — ' ' Serai " siliceous conglomerate, coarse 

 sandstone and shale, including coal-beds, 1100'. 

 Coal-measures. — 2000'-3000'. 



POST-PALEOZOIC OR APPALACHIAN REVOLUTION. 



Paleozoic time closed with the making of one of the great mountain 

 systems of North America — the Appalachian, besides ranges in other lands, 

 and in producing one of the most universal and abrupt disappearances of 

 life in geological history. So great an event is properly styled a revolution. 



