@Byrdie posted:From what I've read lots of scrap coal is use, material of inferior quality with a high concentration of coal dust. The particulate mater in the dusty coal is picked up in the blowers
What "blowers"?
as the locomotives labor up the hill and partially burned cinders are exhausted through the stack. Makes the night shots look like a fireworks display. I don't know that my sources are particularly knowledgeable but it seems like a reasonable explanation to me.
Quite logical.