The steam tractor running the sawmill was running on firewood.
I know because I took my 7 year-old nephew along for the day. He stood there in awe as all these behemoths huffed and chuffed, with the ball governor on this one spinning, then listening to it load down as the saw took a big bite into yet another tree trunk.
The owner saw this young boy standing there, asking me a blizzard of questions, and invited him to come on board and stoke the firebox with the split and stacked firewood seen in the hopper boxes at the cab end. So that's exactly what they did, stoked the big fellow, closed the firebox door, and watched the steam pressure gauge as it dropped momentarily after he was allowed to pull the steam whistle chain for just a second or two. I don't think I've seen a happier kid in a long time. I can guarantee he'll call his uncle next summer to go do it all again, and I'd do it in a heartbeat.