1 122 PRINCIPLES OF STRATIGRAPHY 



similarity of superposition and lithic identity were taken as the 

 guides to synch roneity, a proceeding which naturally led to many 

 erroneous correlations. Thus McClure and Eaton in their early 

 studies of the rocks of the United States were entirely guided by 

 superposition and lithic and structural character of the rocks, their 

 classification being modeled upon that of Werner. Both McClure 

 and Eaton identified the undisturbed Palaeozoic formations of east- 

 ern United States with the Secondary or Mesozoic formations of 

 England, being thus influenced in their correlation by another cri- 

 terion, namely, the relative position of the strata. Lithic similarity 

 caused Eaton to identify the Rochester shale of New York (Lower 

 Siluric) with the Lias of England (Lower Jurassic). Lithic sim- 

 ilarity and similarity of superposition led many of the early geolo- 

 gists to identify the Potsdam sandstone and the quartzose sand 

 rock of Vermont as of the same age, though one is Upper and 

 the other Lower Cambric. In the same manner lithic similarity 

 led some of the earlier geologists to identify the L^pper Cambric 

 or early Ordovicic. Lake Superior sandstone with the Triassic sand- 

 stone of New Jersey and the Connecticut \^alley. while the ribbon 

 limestones of Pennsylvania and New Jersey, of Cambric and Lower 

 Ordovicic age, and the Waterlimes of the Hudson River region — of 

 Upper Siluric age — were not so long ago thought to be stratigraphic 

 equivalents, on account of their great similarity in lithic characters. 

 Superposition, sometimes erroneously inferred, similarity of lithic 

 character, and superficial comparison of fossils led Bigsby in 1824 

 to identify the Rideau sandstone of Kingston, Ontario (Lower 

 Ordovicic), with the Medina of the Niagara and Genesee gorges 

 (Lower Siluric), and both with the Old Red .Sandstone of Eng- 

 land, on account of lithic resemblance of the two formations, and 

 the apparent similarity of fossils in the limestones overlying them. 

 In his later investigations Eaton, like Bigsby, made use of fossils 

 in correlation, but the comparisons made by both were of the 

 crudest, being chiefly by classes of organisms. Thus the Ordovicic 

 conglomerates opposite Quebec were correlated by Bigsby with the 

 "Carboniferous limestone" of England, because both contain re- 

 mains of trilobites, ''encrinites," "corallites" and other fossils. An- 

 other of the early correlations of formations by lithic characters was 

 made in 1821 by Dr. Edwin James. He considered that the sand- 

 stone of Sault Ste. Marie (Cambric or early Ordovicic) the Trias- 

 sic sandstone of the eastern foothills of the Rocky Mountains, the 

 Catskill, Medina and Potsdam sandstones of New York and the 

 Newark sandstone of New Jersey were of the same relative geologic 



