chute 2 is likewise capped which has the double effect of preventing splashes of molten material and reducing the cooling of the glass as it passes from the cupola furnace to the reservoir which path may be long in certain circumstances up to approximately 10 meters since the tapping aperture 9 is preferably exactly vertical with respect to the first wheel 6 and it is not always possible or even desirable to dispose the cupola furnace too close to the fiber drawing machine it should be noted that the use of electrodes provides further means for alerting the operator if there is a need to drain the melt when the level of cast iron increases and is close to the limit level illustrated at 26 in fig3 the electrical current passing through the mass of molten glass decreases greatly as iron is far more conductive than glass the chute 2 melting pot 4 and pouring spout 5 are preferably formed by double walls 19 of refractory steel cooled by intense circulation of water from duct 20 such that a protective layer 10 of devitrified glass is formed the base 21 of the melting pot 4 in which the cast iron discharged from the cupola furnace 1 accumulates is itself made from refractories for example of the type lined with carbon it is provided with an opening 11 which may of course be blocked and through which the cast iron can be drained the pouring spout is made in a similar manner and is mounted so as to be detachable from the assembly in order to minimize problems when replacing the pouring nozzle the flow rate of the feed 17 to the fiber drawing machine is.