42 THE PHYSICAL FEATURES OE CECIL COUNTY 



State Geologist of New Jersey and had been studying for some years 

 the clay beds of the New Jersey Coastal Plain, which he grouped 

 together under the name " Plastic clays." A continuation of these 

 beds southward into Cecil county has shown them to be the youngest 

 member of the Potomac series in that region. Following Cook, Pro- 

 fessor P. P. Whitfield investigated the same beds from a paleonto- 

 logic point of view, but called them Paritan clays, using the name sug- 

 gested by Conrad in 1869; and a little later, Professor Newberry dis- 

 cussed their flora but changed the name of the beds to Amboy clays. 



In the year 1884, Professor "W J McGee proposed for the first 

 time the name " Potomac " for the great series of clays and sands 

 which are now in eluded in the Potomac group. McG-ee continued 

 his work through a number of years and investigated the Potomac 

 beds along the Atlantic Coast, publishing papers from time to time 

 indicating the progress of the work, and finally summed up the salient 

 results of his investigations in the most comprehensive paper of the 

 series, entitled " Three Formations of the Middle Atlantic Slope." 

 Prom this time there was no longer any doubt that the great deposits 

 of clays and sands lying at the base of the Coastal Plain formations 

 should be separated as a distinct group from the rest. 



Attempts were now made to subdivide the Potomac. Professor 

 Philip P. Uhler, while Mc Gee's work was still in progress, had also 

 been engaged in the examination of that portion of the Potomac beds 

 which lie within the Patapsco basin. His investigations led him to 

 separate these beds into three members, termed, beginning with the 

 oldest, Baltimorean, Albirupean, and Alternate Clay Sands. A few 

 years later, in 1883, Darton separated the Magothy from the rest of 

 the Potomac, and in 1885 Eester P. Ward, who, for a number of 

 years, had been carrying on an elaborate and minute examination of 

 the Potomac beds, separated them into the James River series, the 

 Pappahannock series, the Mt. Vernon series, the Aquia Creek series, 

 the Iron Ore series and Albirupean series. While these later investi- 

 gators were prosecuting their work, Professor W. B. Clark and Mr. 

 A. Bibbins were also engaged in a most thorough study of the Poto^ 

 mac series throughout New Jersey, Delaware and Maryland. A 



