Observations on extensive air showers VIII. The distribution in declination and curvature of the shower front

A directional Čerenkov counter has been used at latitude 52° N to separate shower directions into two classes, incident from North and South of the East-West plane through the zenith. Evidence from some previous experiments indicates a Northern excess of approximately 30%. No excess has been observed; out of 526 showers, each containing at least 3 × 10 6 particles at sea level, 261 were incident from the North, and 265 from the South. The apparent direction of a shower was found to be dependent on the position of its axis relative to the detector. A directional radius of curvature was measured, making reasonable assumptions, and found to be 1625 ± 505 290 metres.