This first model used the flue on top to vent the products of combustion. The gas burner heated a radiant panel that was supposed to provide heat into the drum like an electric element. Needless to say, efficiency suffered and the design was soon changed to pass the heat of the flame along with the by-products of combustion through the drying chamber. I think more information about this can be found by searching the Imperial Archives.
I have always had a very special interest in Gas Clothes dryers of this vintage. Both Commercial and Domestic.
I wish someone would offer a Galvanized Steel Clothes Dryer with drum perforated. The burner "chamber" above the opening of the drum. Exhaust below. They were so much faster. (Commercial Gas dryers have always used this arrangement) I would buy one in a heartbeat. With todays electronics and programs. A raw gas flame or electric element can be very controlled. With this type of drying cylinder you can get so much heat in and out very fast. (Not to mention the moisture) Big BTU burner and good size blower. Quick.
That is so interesting Tom about the first run of the Hamilton Dryers having a Manifold. Very cool.
Brent