44 



THE DEVONIAN AND CARBONIFEROUS. 



[BULL. 80. 



fi- 

 ll. 



i. 

 3k. 



I. 

 m. 

 ». 

 n. 



n. 

 o. 

 o. 

 P- 



P> 



a- 



Carboniferous system. 



Upper Coal and Fresh- water lime 



Lower Coal Measures 



Millstone grit 



Carboniferous limestone 



Old Red Conglomerate 



Corustone and marls of Old Red }0\d Red system. 



Tilestone of Old Red 



Upper Ludlow rock.. "\ ^ 



• S Wenlock... 1 



.Upper Silurian 

 rocks. 



> Silurian system. 



Lower Silurian 

 rocks. 



Silurian System.. 



Aymestry and Ludlow i Lmllow 



limestone 



Lower Ludlow rock.. 

 Wenlock limestone. 



Wenlock shale 



Upper Caradoc (with ) 



limestone) > Caradoc. ..•") 



Caradoc sandstone . .. ) t 



Llandeilo Hags (and ) Llamleilo .. ( 



limestone) ^ J 



r. Upper Cambrian (beds of passage) ? Cambrian system (part 



8. Slaty Cambrian rocks ) of). 



M. de Verneuil 1 gave the following classification: 



( 1. Coal Measures and Millstone grit. 



Carboniferous System ^ 2. Mountain limestone. 



Lower Carboniferous shales. 



Upper Silurian (including Old Red sandstone and 



Devonshire strata). 

 Middle Silurian. 

 Lower Silurian. 



Thus evidently following Murchison, and he pointed out the error of 

 Foster of Ohio and other American geologists in identifying limestones 

 containing Silurian fossils as " Mountain limestone." 



In the same journal, in the following year (1841), J. W. Foster ex- 

 plains that the Silurian fossils came from a formation wrongly called 

 by him u Mountain limestone." 



In a review of the report of the geological and agricultural survey 

 of the State of Rhode Island, by Charles T. Jackson, 2 the reviewer gave 

 the following opinion: "In determining the geological age of rocks 

 Br. Jackson gives a preference to superposition of strata and the 

 mineralogical composition over zoological and botanical characteristics, 

 which, however, he allows to be of great value. He prefers also 

 the Wernerian division of Transition rocks to the names Cambrian 

 and Silurian proposed for certain groups iu England, which he thinks 

 will never be regarded in this country as appropriate terms for our 

 rocks." 



This is an indication of the prejudice which is not confined to the old 

 geologists or to the early stages of geological science, but which 

 troubles us at the present time. The names "Cambrian" and 

 "Silurian," within 10 years of the time when Jackson wrote this, were 

 almost universally adopted by Americans whenever the formations 

 included under these names were under consideration, and the Wer- 

 nerian system, for which Jackson and many of his associates at that 



1 Vernenil, Ed.de: Surl'importance de la limite qui separe le calcaire montagne des formations qui 

 lui sont inferieures. Soc. g6ol. France, Bull., 1840, vol. 2, pp. 166-179. 



2 Am. Jour. Sci., vol. 40, 1840, pp. 182, 183. 



