The Furnace, The Human Body

As humans, we stoke the fire which keeps our bodies moving, like coal to a train. I am the furnace which produces no soot, no accumulation. Logs are added to the stone bottom and they catch and vanish, leaving no trace. While it is not good to gather too much soot without sweeping the furnace out, it is equally not good to have so efficient a furnace that there is no residue. Without the residuals of fuel, there is little pay off, like putting money in a bank without earning interest. The soot from a furnace, after all, goes on to nourish a garden and bring further growth and prosperity.