Some layers presenting the space lattice pattern of the metal (Be, Mg, Al, Mo, or Ni) were heated for constant periods. Beginning with a distinctly marked threshold temperature, the interference rings of the oxide space lattice appeared while, simultaneously, the metal space lattice pattern diminished, entirely disappearing with another higher lying temperature. The oxidation temperature ranges (for ten‐minute heating periods) of Be, Mg, and Al were measured. With glucinum it is equal to that within which, Kollath stated, there was a strong increase of the emissivity of beryllium secondary emission cells.An elementary calculation gives an inferior time limit to oxidation of the observable surface layer. The surface layer of polished metals is considered; the high secondary emissivity in the case of glucinum, together with the usually supposed Beilby layer giving only two broad diffuse diffraction rings, points to the existence of a random liquid‐like network of BeO molecules on the surface of polished beryllium secondary emission cells.