1284017 Zone melting COMMISSARIAT A L'ENERGIE ATOMIQUE 29 July 1970 36724/70 Heading B1S [Also in Division F4] Apparatus for growing crystals comprises a water cooled furnace body 10 provided with a base 12, a domed cover 14, resistance heating elements 36 and a melt containing crucible 16. In operation, a crystal is pulled from melt 34 under vacuum, or in a nitrogen, argon or, helium or reducing atmosphere introduced via inlet 44 and plenum chamber 40, whilst the crucible 16 and the crystal pulling rod 20 are rotated by their respective motors 50, 50'. The crystal is pulled by rod 20 being raised, the crucible 16 likewise being raised at a relative rate determined by the desired crystal growth rate. This desired raising is effected by corresponding raising of the crucible and rod supports 52, 52' along hollow columns 54, 54' to which the supports are splined, in response to the drives from motors 56, 56', 58 and 58' transmitted through screw and nut gearing (Fig. 4 not shown) mounted within the columns. Once a desired crystal length has been pulled and detached from melt 34 and subsequently cooled, jack 80 raises shaft 72, and with it lateral arms 70, 88 which carry the cover 14 and the crystal pulling rod 20 with its drive and support means, respectively, so that cover 14 and rod 20 together with the crystal grown on it are moved clear of furnace body 10. In this raised position (Fig. 2 not shown), keys 76 on shaft 72, which previously prevented the shaft 72 rotating, by running in keyways 78 in bearing members 74 used to guide and mount the shaft, are raised clear of the keyways 78, to allow rotation of the shaft 72 and so pivoting of the arms 70, 88 and the cover 14 and crystal puffing rod 20 clear of the furnace body 10, whereby the crystal may be removed from the rod. Slots 77 in a U sectioned supporting frame 28 which carries the bearing members 74, limit the degree of pivoting of the arms 70, 88 to an amount just sufficient for the rod 20 to swing clear of furnace body 10. Clear access to furnace body 10 or crucible 16 may be obtained after withdrawal of rod 20 from cover 14 by swinging the latter about pivot pin 68 clear of the furnace body (Fig. 3 not shown) after release of latch 71.