Engineering--Pennsylvania--Philadelphia 3 Engineering--Problems, exercises, etc 3 Engineers--Pennsylvania--Philadelphia--19th century 2 Science and engineering--Pennsylvania--Philadelphia--20th century 2 Bessemer process 1 Business--History--Pennsylvania--Philadelphia--20th century 1 Canals and railroads--19th century 1 more ... Centennial Exhibition (1876 : Philadelphia, Pa.) 1 Clubs and Associations--Philadelphia--20th century 1 Delaware & Schuylkill Canal 1 Engineering firms--United States 1 Engineering proceedings 1 Engineering--Education 1 Engineering--Pennsylvania 1 Engineering--Social aspects--United States 1 Engineering--Societies, etc 1 Engineers--19th century 1 Pennsylvania Railroad--19th century 1 Philadelphia (Pa.)--History--20th century 1 Philadelphia (Pa.)--Social conditions--20th century 1 Philadelphia Views--Street Scenes--19th century 1 Philadelphia views--Street scenes--20th century 1 Railroad engineering 1 Railroads--Pennsylvania--19th century 1 River engineering--Pennsylvania--Philadelphia 1 Science and Engineering--Notes 1 Separation and divorce--19th century 1 Sewerage--Pennsylvania--Philadelphia 1 Smallpox--Pennsylvania--Philadelphia 1 Social life and customs--Pennsylvania--Philadelphia (Pa.)--19th century 1 Steel 1 Steel--Standards--United States 1 Taverns (Inns)--Philadelphia--History 1 United States--History--Civil War, 1861-1865--Personal Correspondence 1 Voyages and travels 1 Weather--Personal accounts 1 World War, 1939-1945--Personal narratives, American 1 less ...