Diagram from sewage treatment plan for Philadelphia, 1912
Centre Square Water Works, Frederick Graff, Sr. Plans, 1799
Steam engine drawing, Frederick Graff Sr., 1815
Color Diagram of Plan for the Collection, Purification and Disposal of the Sewage of the City of Philadelphia
69th St. Sewer and Culvert across Lansdowne AVe.
Ventilating cover for manholes
Plan for the Collection, Purification and Disposal of the Sewage of the City of Philadelphia, 1912