Sawdust cyclone

About 5.5' in diameter at its widest point and about 7' long. An enormous chunk of rust. From "Wood Burners", by Daniel Mihalyo, Princeton Architectural Press:

"Their function was to funnel planar shavings and particles of sawdust into the burner. These particles were blown through a pipe into the cyclone from the mill itself."

The sawdust pipe coming from the mill can be seen in other photos in this series.