The arrival directions and mass composition of cosmic rays above 10¹⁸eV

Data on the arrival direction distribution and mass composition of cosmic rays above 10¹⁸eV are briefly reviewed. There is no compelling evidence for wide‐angle or point‐source‐like anisotropies and the mass composition above 10¹⁷eV is constant to at least 5×10¹⁸eV: a mixture of protons and Fe nuclei can describe the data. There is weak evidence that the mean mass increases above 5×10¹⁸eV but, as with this and with the arrival direction problem, a vastly greater and better data set is required. This could come from an instrument with an aperture of 10⁴ km² sr.