[Geological Survey of Pennsylvania ; J.P. Lesley, state geologist, anthracite district ; Charles A. Ashburner, geologist in charge ; A.W. Sheafer and Frank A. Hill, assistant geologists]
Date
1882
Series
Report of progress (Geological Survey of Pennsylvania) ; AA
compiled from the Survey by Richard H. Sanders, A. Dw. Smith ... [and others] Topographical map of the Blue Mountain at Port Clinton in 2 sheets / surveyed and drawn by George M. Lehman. --
Date
1881-91
Series
Report of progress (Geological Survey of Pennsylvania) ; AA Atlas Suppl. 2