It will be seen that the current of steam can be regulated by moving the tuyere, D, from or toward the eduction orifice.
The harder the air is driven into the fire above the tuyere the more oxygen is furnished and the hotter the fire becomes.
Danger of explosion: Coal gases leak into the tuyere when the blast is shut off.
Directly below the tuyere is an opening through which the ashes that drop from the fire may be cleaned out.
The tuyere for a furnace-blast found at Fasagh (see illustration) is another evidence of that skill.
But the principle of the tuyere, where the blast enters the forge, is the same as we blacksmiths have always used.
The steam enters through the tubulure, A, and finds its way around the periphery of a tuyere, D.
The air necessary for the combustion is sucked through the interior of the nozzle, H, which is in front of the tuyere.