Water by Gravitation from the Perkiomen, Birkinbine 1866
Preliminary Surveys for Procuring a Supply of Water by Gravitation for the City of Philadelphia from the Perkiomen, by H. P. M. Birkinbine, 1866
Preliminary Surveys for Procuring a Supply of Water by Gravitation for the City of Philadelphia from the Perkiomen, by H. P. M. Birkinbine, 1866