The fireplace would have been used to heat branding irons for branding barrel heads of flour barrels. The original level of the mill's basement was originally 2 to 3 feet lower. The attic had storage bins or garners for grain and tempering bins. The second floor had room size bins in the area above the miller's office end of the building. How It Works 1.
Different grains go into different chutes and into different bins on the second floor.
The action removes any mold that may have grown on the grain or dirt that may be physically attached to the grain. This is where the major work takes place. The ground grain is now warm and moist flour. Flour falls through the finest mesh. And the bran, the coarest, falls out the end.