60 THE DEVONIAN AND CARBONIFEROUS. [bull. 80. 



the lines between the "Chainplaiu" and " Ontario," or the " Ontario" 

 and " Helderberg divisions," and this part of the classification has 

 accordingly fallen out of use, because useless. 



Like objection exists to the term " New York system." While the 

 base is well marked, the rocks of Pennsylvania, to the top of the Coal- 

 Measures, should be added to them to complete the system. Adding 

 the Carboniferous system, as expressed in Pennsylvania, Ohio, and Vir- 

 ginia, a natural group of the first order is produced which nearly cor- 

 responds to what we call the Paleozoic era. Were we to adopt for this 

 grand terrane the name Appalachian group, we should have a properly 

 constituted name for an actual, existing geologic group, free from 

 theory, and its use would probably assist in the progress of science. 



This classification of the New York State survey is further defective 

 in the retention from the old nomenclature of such definitive terms as 

 Corniferous, Eucrinal, Water-lime, etc. Intrinsically they are not dis- 

 tinctive of any particular stage and therefore do not fulfill the true pur- 

 pose of names for the stages. 



A similar objection holds in the case of such names as Cauda-galli 

 grit, Pentamerus limestone, and similar terms. Although the fossils 

 indicated may characterize the formations so named in their typical 

 outcrops, the fossils may fail in the geographic extension of the forma- 

 tion, or further study may show that the fossils are not confined strati- 

 graphically to the zone represented by the particular formation in 

 question. 



The only kind of name which can be applied without objection to the 

 ultimate subdivisions of the terranes, is a binomial term composed of 

 the lithologic name of the rock and the geographic name indicating its 

 typical exposure. 



The use or the name "Old Eed sandstone system" has been dis- 

 carded, and its use in 1843 indicated that the name system gave such 

 dignity to a terrane that it was supposed necessary to find it in every 

 complete section of rocks. It was later that geologists agreed that the 

 Old Red sandstone represents the Devonian system, but represents it 

 in a different type of deposits. 



The imperfection in the nomenclature, even at the present time, is 

 seen in the fact that English geologists x still use the phrase " Devonian 

 and Old Red sandstone " for the rocks between the Silurian and Car- 

 boniferous systems. This error and confusion comes from the difficulty 

 in ridding ourselves of the old notion that the age of rocks may be in- 

 dicated by their lithologic or stratigraphic characters. Age can be 

 indicated only by something which persists through time; the litho- 

 logic characters of rocks indicate what they were made of and how ; 

 the stratigraphy indicates the *order of sequence. The age of rocks 

 can be indicated only by something which changes with the passage of 

 time according to some definite law. The organisms represented by 



1 1887. Goikie Text-Book: Woodward's Geology of England and Wales. 



