smd4 posted:
"At ordinary working pressures, the difference between the temperature of the water in the boiler and the water of the entering feedwater is about 200 degrees F. When the engine is working the circulation is rapid and the temperatures soon equalize, but if the engine is standing, the temperatures equalize more slowly; the cooler water settles around the firebox sheets and damage results from the contraction that follows." (emphasis added)
--ICS, Locomotive Management, 1928, 1937
"When the engine is working the circulation is rapid and the temperatures soon equalize,"
