Some experimental results are here compared with calculations previously communicated. Wurtzite crystals from Thrace show a high degree of disorder which cannot have arisen from transformation of parts of the crystal into zincblende. The rhombohedral modification of carbon seems to be the more stable one at low temperatures. Rotation photographs of SiC (II) crystals show a low degree of disorder and the general course of the diffuse scattering resembles that of a slightly disordered crystal of the SiC (III) type.