Hi. D. Campbell—The Potsdam Group, Virginia. 471 
Archzean rocks, consisting of granulite, syenite and rocks of a 
gneissoid character. The river then leaves the mountains 
about at right sels é 
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MAP OF THE JAMES RIVER GoreEr at BALCONY FALLS, VIRGINIA, 
Scale, 4,000 feet = 1 inch.— VERTICAL SECTION ALONG THE LINE A-B ON THE Map, 
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_ The sandstones and slates from these Archean rocks to t 
Western limit of the gap have been classed as mlemery = 
Lower Cambrian. Starting from the Archean axis of the 
