Abstract
Measurements are reported on the arrival direction distribution of over 70000 carefully selected showers with energies above 6*1016 eV detected at Haverah Park since 1963. After showing that spurious effects do not significantly perturb the data the authors find that the probability of isotropy in the energy region 6*1016 eV to 1020 eV is less than 3% and that there is evidence to suggest that the arrival directions are complex functions of energy and declination. There is a significant anisotropy of about 2% in the first harmonic of right ascension in the direction 251 degrees for energies near 1017 eV, and a significant 6% first harmonic in the direction 46 degrees RA for energies near 1018 eV. Some of the particles of highest energy arrive nearly perpendicular to the Galactic Plane.