In the early 50s, I don't think I was even 8 years old, my father took me to a coal mine. We took his 1949 Plymouth coupe up Fairview Canyon to the top of Huntington Canyon. The coal mine had a horse-drawn hopper; I was given a helmet & loaded in the hopper, then with my Dad beside the drover, we headed into the mine shaft. At the end of the shaft were miners ready to load the hopper with coal from the mine face; while the drover hooked the horse up to the other end of the hopper. My Dad & I had to walk back-out, up against the wall to avoid the hopper as it came back and forth. (Also there was a crew starting a side tunnel with a drill.)
We couldn't ride-out because at the mine opening, the horse with the drover behind would veer to the side after the drover had pulled a pin releasing the hopper straight-ahead to hit a bumper, dumping the coal into the top of a chute - a coal truck could then be loaded from the chute below.
I wonder about the hazards to the horse; for example, the pin not getting pulled - a horse once spooked may never work in the mine again.
Addendum: This blurb not a MyStory but my Dad's story ... in coal towns like CastleGate, they raised canarys for use in the mines, but there were canarys that never sang - sometimes the canary in the coal mine did not die, it just never sang again.
James A. BELL