The 4835 and 4868 are hauling an eastbound manifest through Columbia as their engineer yanks the horn cord for Walnut and Locust Streets. The silver piping in the foreground carried compressed air to the track switches controlled by the operator in COLA Tower. An MW foreman told me at the time that the air-operated switch points slapped into position with enough power to crush rocks, so it was best to steer clear; commonsense, but it got your attention. The 4835 was built by Baldwin/PRR/Westinghouse in July, 1935, nearly 42 years prior to the photo date.