590 DISCUSSION ON THE 
(1) The first fact is the complete uniformity in distribution of the cosmic 
rays within the present limits of experimental error in the measurement of 
their intensity. This has been disputed by some, but I should like to 
show how I have been testing it this summer. I have the results of a 
continuous month of cbservation of the intensities of the cosmic rays 
taken through four daily six-hour periods as follows: 6 a.m. to noon, 
noon to 6 p.m., 6 p.m. to midnight, and midnight to 6 a.m. None of the 
means of intensities in these four periods differ by so much as one-half 
of one per cent. The barometer which, as Cameron and I first showed 
in 1925,° influences markedly these intensities, was extraordinarily 
constant during this summer month in Pasadena, scarcely varying 3 mm. 
either way from the mean throughout twenty-five days ; the barometer 
readings go through a small minimum each afternoon, due to currents 
set up by the sun’s heat, and a small maximum early each morning. The 
cosmic rays, on the other hand, go through a small afternoon maximum 
and an early morning minimum, thus showing quite conclusively, I think, 
that the minute variations in cosmic ray intensities are not due to 
radiations from the sun, which is shining during both maxima and minima, 
but rather to slight variations in the atmospheric blanket induced by the 
alternate heating and cooling of the gaseous matter through which the trays 
reach the earth. Further evidence for the correctness of this conclusion 
is found in the fact that the period from midnight to morning, during which 
the atmosphere is more quiet than is the case in any of the other three 
periods, shows the smallest variations in the individual readings, thus 
appearing to indicate that these, too, are due to atmospheric disturbances. 
The conclusion is consonant, too, with the latest, very exact measurements 
of Hoffmann’ at Halle, though the conditions in central Europe are less 
favourable for testing the especial points brought to light im my own 
work. 
This independence of the cosmic ray intensities of the positions of the 
sun, the Milky Way, or other celestial objects is the most amazing property 
of these rays, since it seems to show quite definitely that those portions of 
the universe—better, those directions in the celestial dome—in which 
matter is most abundant, such as the directions of the sun or the Milky 
Way, have no advantage over those directions in which matter is very 
scarce. J can see no possible escape from the conclusion that the con- 
ditions existing in those portions of the universe where matter is abundant, 
that is, in and immediately about the stars, are inimical to the formation 
of cosmic rays. This in itself bars out the likelihood of their being due to 
the annihilation of protons, provided such annihilation is to be called 
upon, in accordance with the demands of most modern astronomers, for 
maintaining the temperatures of the stars. In making this statement I 
am eliminating as scientifically unacceptable the hypothesis that in bygone 
ages these rays were created by processes no longer existing and have 
since been wandering like lost souls about a universe from which there is 
for them no possibility of escape. Further evidence on this point will be 
presently given. 
6 Millikan and Cameron, Phys. Rev., 28, 856; 1926. 
7 Hoffmann, Zeit. fiir Physik, 69, 703 ; 1931. 
