THE DEVONIAN AND CARBONIFEROUS FORMATIONS 



OF NORTH AMERICA. 



By Henry S. Williams. 



INTRODUCTION. 



THE STATE OF OPINION AT THE BEGINNING OF THE PRESENT 

 CENTURY REGARDING THE CLASSIFICATION AND NAMING OF 

 GEOLOGIC FORMATIONS. 



THE STATE OF GEOLOGICAL OPINION PRIOR TO 1835. 



Upon reviewing the works of geologists written in the early part of 

 this century, we find a very well marked school of opinion pervading 

 all the works of English and American geologists, who published their 

 works prior to the year 1835. A gradual change was taking place 10 

 years before this, but it was not until after 1835 and about 1840 that 

 the new school of opinion, as expressed in modern classification of 

 geological deposits, became generally adopted. 



The prominent English text-books upon geology which appeared prior 

 to that date are those of Maclure, 1817 ; Maculloch, 1821 ; Eaton's 

 "Index," 1820; "Erie Canal Bocks," 1824; Conybeare and Phillips, 

 1822 ; LyelFs " Principles," 1830 ; De la Beche, first edition, 1831. 



All these books are based upon the general principle for the propa- 

 gation of which, if not for the entire origination of the idea, Werner is 

 distinguished. This idea which characterized the Wernerian school 

 consisted fundamentally in the attempt to classify geologic deposits by 

 the minerals which they contained and their petrographic characters. 



Abraham Gottlob Werner (1750-1817), who has been called the father 

 of German geology, was undoubtedly the founder of the classification 

 of rocks into formations arranged in stratigraphic order. 



Although his " theory of formations" has been superseded by other 

 theories, the proposition that the crust of the earth is divisible into 

 formations and that these formations have a regular order of sequence 

 in relation to one another is at the very foundation of modern geology. 



Werner was an enthusiastic teacher, but he wrote little, and we are 

 obliged to look to the writings of his pupils and their followers for an 

 exposition of the views which formed the basis of geological science at 

 the beginning of the XIX century. 



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