Abstract: Furnace apparatus and method, for the continuous electric heating or fusion of particulate mineral-bearing substances, wherein a cylindrical furnace housing is adapted to trunnion bearing, the housing having at least one detachable and elongated conical extension at ends for dumping, the extensions likewise having electrode openings which are coaxially aligned with the housing, whereby a charge of the mineral-bearing substance may be introduced either during fusion or heating or roasting or firing, thus permitting partial filling of the furnace housing and sequential build-up, protecting the respective ends of the furnace against dead space and excessive charge recycle. By virtue of design, the conical ends are shielded against burning out by unbearable heat generated from the electrode arc. Inherent advantages occur by highly accelerated rotation, yielding resultant centrifugal forces which are applied to the charge.