FLOKA OF OLDFl! I'O'iTniAC FOI;^F\TI()^■. :'.o9 



iiivsclf. Aftoi- two (Inys spciil in ihc iniincdinlc vicinity of \\';isliiiii:;l()ii 

 we coiimuMiccd llic jc.unicy soutliwni-d iiilo \'ii-<iinia. 'riic plan was lo 

 follow Iho ^'oun^ci- Mosozoic hell, zigzagsinjl freciuently across it to 

 examine its huulward and coastward niar<iins and llie contact with 

 l)otli th(> underlyinsi crystalline and Paleozoic rocks and tlic overlyino; 

 Tertiary deposits. Thus by easy stajjes l''re(lerickshur<i was reacluMl 

 on Aujiust 1 and liichmond on the Sth. I'roni Itichniond an excui'sion 

 was made in a rowhoat down the .lames and up the Appomattox to 

 Petershm'sr. I'-iilht davs \v(mv si)ent in this rejiion, and on the ISth the 

 soulliwai'd journey was I'esumed in the attempt to trace the formation 

 in that direction. The locality mentioned by Ifojivrs on the Nottoway 

 Ui\('r at Hollinjis liridge" as the most southerly point at which he had 

 IxHMi able to find an exi)osuiv of the formation was visited, and it was 

 fomid with chai'acteristic clay balls in the bed of the river underlying 

 the ]';ocene. The l)est exposure was close to Boilings Bridge, but it 

 was also found at Fields Bridge, 4 miles ahove, which is undoubtedly 

 Rogers's locality. The reconnaissance was continued to the Roanoke 

 at Weldou, opposite which, near the railroad bridge, beds wer(> found 

 closely reseml:)ling those of the Okler Potomac, but the exposures wei'e 

 not decisive on this point. The expedition then returned to Peters- 

 burg, Richmond, Fredericksburg, and Washington, varying the route 

 as much as possible and examining many additional localities and 

 exposures. The party reached Washington on the 25th, but resumed 

 opei'ations on the 27th and traversed the State of Maryland, following 

 the Potomac outcrop as before. The iron-ore region was carefully 

 examined, the only plant remains found being pyritized lignite and 

 silicified wood. The cycadean trunks collected tiy T>-son, and then 

 at the Maryland Academy of Sciences, were shown us b\- Prof. P. I{. 

 Uhler, president of the academy, and permission was given us to have 

 photographs made of them, which was done a little lat(M'. Professor 

 Uhler accompanied us to many localities with which he was familial'. 

 Considerable time was spent on the coastward margin on the forma- 

 tion, where its relations to the overlying marine beds were studied. 

 The reconnaissance was concluded on the 31st, a clear conception hav- 

 ing been acquired \)\ all the members of the party of the general nature 

 of the Potomac formation. 



"Report for \fiX), p. 17. 



