THE NAME " NEWARK" IN AMERICAN STRA TIGRAPHY. 59 



graphy are ( i ) definite association of the geographic feature with 

 the terrane, (2) freedom of the term from preoccupation in 

 stratigraphy, (3) priority. The rule of definite association is 

 satisfied if the geographic feature, being a town or district, is 

 wholly or partly underlain by the terrane, or if, being a stream, 

 it crosses the terrane. Preferably the portion of the terrane 

 thus associated should be petrographically and paleontolog- 

 ically characteristic, but this consideration yields to priority. 



The " Newark " rocks underlie the City of Newark, exhib- 

 iting typical phases of sandstone and shale and containing 

 some fossils. The only other rocks present are of widely dif- 

 ferent character, being Pleistocene. The name Newark has been 

 applied to no other terrane. It is the earliest geographic 

 name proposed for this terrane.^ 



G. K. Gilbert. 



II. 



Mr. Gilbert has very kindly invited me to answer his argu- 

 ment : (i) that the so-called Newark system ought to have a 

 name, because it is a stratigraphic integer, or unit; (2) that a 

 stratigraphic name ought to include a local geographical term ; and 

 (3) that the name Newark is the proper one, because of (a) the 

 definite association of that geographical feature with the rock 

 beds in question, (b) the freedom of the term from preoccupa- 

 tion in stratigraphy, and (c) its priority. 



I. He considers that the stratigraphic unit is peculiarly defin- 

 ite from the conspicuous unconformities at top and bottom, while 

 internally it is conformable throughout with little varied com- 

 position. 



In eastern Pennsylvania, where the rock beds have been 

 studied with some small approach to thoroughness, the compo- 

 sition is found sufficiently varied to justify at least five very con- 

 spicuously marked subdivisions of several thousand feet each. 

 Almost all the fossils hitherto used for inferring the age of the 



^ See American Geologist : Russell, Vol. 3, p. 181, and Vol. 7, pp. 238-241; 

 Hitchcock, Vol. 5, p. 201. 



