Saturday was light engine day on the Shamokin Secondary. Each Saturday morning a light engine movement would begin in St. Nicholas, taking all the power there, usually five or six units, east. They would stop at Tamaqua and pick up the unit that worked there. Upon arriving at Port Clinton, they would run west to West Cressona where they would pick up another three or four units before reversing direction and running east to Reading, then west on the main line to Enola Yard where all the units were serviced. We see the movement with nine units at West Cressona, preparing to head to Reading and Enola. If I count correctly, the consist included 5 MP15s, 2 SW1500s, and 2 GP10s.