The onset times of a number of Forbush-type decreases observed at four widely spaced stations are compared, and it is shown that appreciable differences occur. The stations selected were Hobart, Mawson, Ottawa, and Sulphur Mountain. It was found that a consistent pattern is obtained for the events studied when the onset times are plotted as a function of the direction of maximum sensitivity of the recorders relative to the earth-sun line. This is interpreted as being due to a directional anisotropy that exists in the mechanism producing the decreases, at least in the early stages. The depression occurs first for particles arriving from directions between 30° and 120° west of the earth–sun line. The relation between these observations and geomagnetic disturbances and the quiet-day daily variation is discussed.

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A Geiger counter telescope has been employed to study μ-mesons incident at large zenith angles. The counters were hodoscoped in pairs enabling the direction and angle of incidence of the particles to be determined. The intensity has been analyzed as a function of arrival time but no significant variation has been found either in solar time or sidereal time. However, a variation in solar time has been noted on analysis of extensive air showers measured concurrently. The angular variation of intensity has been studied and absolute rates obtained; these rates have been compared with those of an earlier determination showing excellent agreement. Some evidence has been obtained of a directional anisotropy in the μ-meson flux as measured at the apparatus.

Enhanced diurnal variations during February 1–6, 1967; April 5–14, 1967; and February 22–28, 1968, have been examined by use of data from several super neutron monitors. It is found that during these days, cosmic‐ray intensity in a direction 40°–70° west of the sun‐earth line was lower with respect to other directions, in particular the polar and antigarden‐hose directions. This anisotropy, which resulted from a reduced intensity in the garden‐hose direction in the ecliptic plane, suggests that the entire diurnal variation observed in cosmic‐ray intensity cannot be attributed to a simple mechanism involving the corotation of cosmic‐ray gas, with the interplanetary field. Corotation of cosmic‐ray gas implies an enhancement of intensity from a direction roughly 90° east of the sun‐earth line (1800 hr direction). Highly variable north‐south asymmetries were also present during these periods. These anisotropies occurred without accompanying geomagnetic disturbances or Forbush decreases indicating that they were not due to solar activity on the visible side of the sun.

is defined by Eq e (5), Ex is the true transition energy, and Eg is the binding energy of the muon in the atom 0 By examining 2T states (T = 1) in O 16 and N 16 , one gets uf-Ef=2.56 MeV. 15 The form factors in the notation of Ref 0 14 are F x = 0.972, F 2 = 3.602/2M, and F A =-1.179. 16 J. C. Taylor, Phys. Letters jLl, 77 (1964), and references given there.