system--that is to say, a mass of brickwork is heated by the waste heat
of the effluent gases, and when that is made sufficiently hot, the
current of waste gases is turned into a second mass of brickwork, while
air is admitted to pass through the brickwork already heated. The system
thus briefly described entails a certain amount of attention on the part
of the workmen in the altering of the valves or dampers to reverse the
currents. The regenerator now adopted consists of an arrangement of six
zigzag flues, three on each side of the setting. These flues run the
whole length of the setting. As indicated by the arrows pointing
downward in Fig. 3, the waste gases on their way to the chimney stack
pass to and fro through the side flues, thus giving up a large portion
of their contained heat by the process of conduction or contact to the
central flue through which the incoming air passes. The air necessary
for combustion is first admitted into a large chamber in the center, and
then it is divided into two currents, which pass right and left into the
central passages of the two regenerators. As the air flue is at a very
bright heat for a considerable distance before the air leaves it, the
temperature of the air must be equally great, or nearly so. In its most
improved form one of these heat regenerative furnaces provides an amount
of heating surface extending to 234 square ft., which is exposed to the
air on its way to the combustion chamber.

Passing from the producer through the flue provided for it, the gas
enters the retort setting underneath the side retorts, where it meets
the air coming from the regenerator. It enters the setting, not by a
number of small openings, but by one large opening on each side, and
meets the air entering also by a large opening, the effect of which is
to avoid the localization of intense heat, as all the retorts of the
setting become enveloped in an intensely heating flame, due to the
combustion of the carbonic oxide and hydrogen gases.