42 Introduction 



HISTORICAL REVIEW AXD BIBLIOGRAPHY ' 



The prominent physiographic features of western Maryland have long 

 been known, since it was on the route of the early trails and roads from 

 the Atlantic to Fort Cumberland and thence across the Alleghany Plateau 

 to the Ohio Valley. In the early years of the nineteenth century the con- 

 struction of the National Road and later the surveys for the Chesapeake 

 and Ohio Canal and the Baltimore and Ohio Railroad were instituted, all 

 of which added to the knowledge of the topography of the countiy and to 

 some extent to its geology. 



The earliest attempt to classify the formations of western Maryland 

 and correlate them with the geologic column as then established in 

 Europe was made by William Maclure in 1809. Maclure accepted the 

 Wernerian classification and divided the rocks of this country into the 

 Primitive, Transition, Flcetz or Secondary, and Alluvial. Apparently all 

 of the Maryland rocks now referred to Devonian were included in Mac- 

 lure's Transition. This article was subsequently revised, enlarged and 

 published in book form in 1817. In this work the highest mountains in 

 western Pennsylvania, Maryland, and a portion of Virginia were referred 

 to the Transition rocks as well as a strip along the banks of the Potomac 

 in western Maryland. It contains a colored geologic map of the United 

 States extending from the Atlantic coast to the western line of Louisiana, 

 Arkansas, and Missouri. The line separating the Secondary and Transi- 

 tion rocks crosses Maryland to the east of Cumberland, all west of that 

 line being referred to the Secondary age, while the Transition rocks ex- 

 tend eastward to or beyond the Blue Ridge. The map published the fol- 

 lowing year in the Transactions of the American Philosophical Society 

 covers a larger area and the line of separation between the Transition and 

 Secondary rocks crosses Maryland considerably west of Cumberland, so 

 that only the extreme western part of the State is represented as of 

 Secondaiy age. 



James Shriver in his account of the surveys and examinations for the 

 Chesapeake and Ohio Canal in 1824, described to some extent the 

 physiography of Garrett County and made slight reference to its geologv'. 



^ Contributed by Charles S. Prosser. 



