end of chute 6 via a pivot connection 22 pivot connection 22 is spaced from the horizontal pivot axis of chute 6 by a distance 34 d 34 the movements of control rod 20 are effected by means of drive components located within a gearbox indicated generally at 24 supported from rotary casing 10 and located within annular chamber 14 gearbox 24 has a vertically oriented rotatable input shaft 26 which is driven via a pinion 28 and ring gear 30 as a result of the combination of relative movements of a pair of additional ring gears 32 and 34 the manner and means of driving gears 32 and 34 so as to impart rotation to shaft 26 while casing 10 is rotating about the furnace axis does not comprise part of the present invention and is described in aforesaid co pending application 65 289 gearbox 24 has at least a first rotatable horizontally oriented output shaft 50 output shaft 50 is coupled to the upper end of control rod 20 via a short connecting rod 36 having a length 34 l 34 see fig2 as may be seen from fig3 the connection of connecting rod 36 to control rod 20 is via an articulated coupling i e a pivot joint 38 fig2 schematically represents several.