About the Energy Interval beyond the Ankle Where the Cosmic Radiation Consists Only of Ultraheavy Nuclei from Zinc to the Actinides

According to recent measurements the tendency of the chemical composition above the ankle is characterized by increasing fractions of intermediate and heavy nuclei and a dominance of light nuclei around the ankle. Calculation of the chemical composition in the range 3.5 × 1018 - 5 × 1019 eV according to new principles explains both the rising tendency of the heavy component. The calculation is prolonged to the adjacent interval 5 × 1019- 2.4 × 1021 eV using the same theoretical background and some features of the observed cosmic-ray spectrum. It results that above the energy of 6.7 × 1020 eV, where the flux is estimated to be 1.8 × 10?30 particles/m2 s sr GeV, the cosmic radiation consists only of nuclei heavier than Zinc. Measurements of the spectrum of present and past experiments are compared with the calculations.