Cosmic ray results
obtained on a journey to and fro between Australia and Japan are described. The
apparatus was that used previously on the H.M.A.S. Wyatt Earp(l), but since
modified, and extended to record showers. A latitude effect of 20 per cent. was found for rays of
vertical incidence. The difference between electron and meson components did
not exceed the statistical errors of 2 per
cent. For wide angle coincidence telescope measurements the latitude effect
reduces to 13 per cent. Further
it has been found that a latitude effect of some 10 per cent. exists for extensive showers of an average spread of
1 metre. An observed latitude
effect of penetrating extensive showers falls, however, within the standard
deviation of the measurements. The above results were not corrected for
barometric and temperature effects nor for variations in height of the
meson-producing layer. Evidence is presented of the existence of a semi-diurnal
variation at the equator and at Kure of opposite phase to the barometric pressure
variations and of about twice the coefficient of the normal barometric effect.
The maximum of the diurnal period occurs at Kure at 2 hours local time and at the equator at 19 hours. A temporary increase of between 2 and 3 per cent.
in cosmic rag intensity during the period July 29-31, 1948, is noted.
The barometric effect in the intensity of near-horizontal cosmic ray muons according to the data of the coordinate-tracking detector DECOR