During the Gila Expedition I relied heavily on fire. It was often the one thing keeping me alive when temperatures dipped below zero. I can't honestly say how cold it was, but from experience I estimate that the lowest temperature I experienced was no greater than -10F.
Every afternoon I would gather a stack of resinous wood from fallen apache pines. The resin allowed the wood to sustain my fire. I longed for an axe that would make the job of harvesting wood easier.
You can also see a coffee can on the other side of the fire. This was used to melt the snow that I had collected.