Charles Emerson Beecher, James Hall, John Peter Lesley and John Simpson Africa, Second Geological Survey of Pennsylvania… (1884)
“ The Second Geological Survey of Pennsylvania was planned and has been prosecuted with a primary view to the material interests of the Commonwealth, the practical study of the rocks, their structure and mineral contents, and to as perfect a description of them as a diligent survey of facts could afford, with maps and sections and occasional photographic views for illustration; and I am happy to know that this conception of the proper nature of a State Survey has been approved by the Board of Commissioners, without reserve ”
