CHAPTER II. 



HISTORICAL REVIEW OF THE GEOLOGIC AND PALEONTOLOGIC 



WORK. 



The scope of this review is limited, with a few exceptions, to the no- 

 tice of papers and memoirs that have added something original to the 

 preexistent knowledge of the rocks and faunas now referred to the 

 Cambrian group. 



Several methods of presenting the historical data have suggested 

 themselves. 



(1) Chronologic; (2) Geographic and chronologic ; (3) Chronologic, 

 geographic, and stratigraphic. 



(1) Chronologic. — This method necessitates reference to papers in the 

 order of their publication, whether they treat of Cambrian rocks in 

 Newfoundland, New York, Alabama, or Nevada. All is subservient to 

 the chronologic record. 



(2) Geographic and chronologic. — This method permits of the chrono- 

 logic grouping of the papers referring to the rocks under consideration 

 in geographic areas. 



(3) Chronologic, geographic, and stratigraphic. — This third and more 

 comprehensive method arranges the review in the form of a statement 

 of the historical data as in the second method, with the addition of 

 treating of such primary divisions separately as may be thought worthy 

 of such consideration. To this there may also be added, in exceptional 

 instances, the chronologic arrangement of the discoveries and opinions 

 of some of the more prominent investigators and authors. 



The second method is adopted in this review in connection with the 

 third, where the latter is necessary in order to present more clearly the 

 evolution of the present knowledge of the rocks and fauna of the Cam- 

 brian group. 



The Cambrian group can usually be divided into three primary divisions. 

 First, the Lower Cambrian ; second, Middle Cambrian ; third, Upper 

 Cambrian. This nomenclature will be used throughout the review, 

 when it is necessary to refer to a standard generally known. 



Bocks of Cambrian age occur on the North American continent in 

 four principal geographic areas or geologic provinces. In reviewing 

 the literature it is possible, owing to the investigators in each province 

 having limited their work to their respective provinces, to present the 

 history of discovery and publication in each by itself, as follows : 

 I. The Atlantic Coast or Eastern Border Province. 

 II. The Appalachain Chain. 

 III. The Rocky Mountain or Western Border Province. 



Bull. 81 4 49 



