| Here is the 23rd of 36 plates constituting the "Centennial Album of Pennsylvania R.R. Photos and Prints." It was published in the April 1946 issue of "Railroad" magazine, page 32. Photo Caption: "Ball Signals. Through truss Schuylkill Bridge, built as part of the Delaware Extension in 1861, displayed ball-signal indications to trains and river traffice, advising position of swing-span." |