This communication presents some experimental results that seem to indicate that the barometric pressure coefficient customarily employed to correct terrestrial neutron monitor intensities is subject to variations in magnitude that are apparently related to changes of atmospheric water vapor content above the site of measurement. An aluminum container was placed above one section of the IGY standard neutron monitor at the University of Denver, Denver, Colorado (1600‐meter altitude, 2.93 Gv/c Quenby‐Wenk threshold). The container was filled to different depths of water for various intervals of time, and the corresponding attenuation of the nucleonic intensity was determined. Preliminary results of a statistically reliable nature have been obtained for four different water levels. The results are indicated m the table below.

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It seemed to be of interest to investigate the emission of alpha particles from rocks and other surface materials of the earth in order to find out whether these processes play an important role in the ionization balance of the lower atmosphere.The alpha emission from surface material was measured with a scintillation counter and photomultiplier tube.The values given for the emissivities of vegetation, rocks, and soils indicate that alpha-ray emission plays a not very important role in the ionization balance of the lower atmosphere.The exhalation of radon from rocks was investigated and a means of correcting for spurious counts due to this cause is explored.

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