http://authors.library.caltech.edu/11133/ Seasonal cosmic-ray effects at sea level Millikan, R. A. Neher, H. V. Smith, D. O. Caltech Library Services By sending a Neher self-recording electroscope in a 10-cm lead shield repeatedly on a slow Norwegian steamer over the route Vancouver-Los Angeles, around South America and return to Los Angeles and Vancouver we find: (1) As heretofore, an equatorial dip, measured from Los Angeles, of 7 percent on the western side of South America, 8 percent on the eastern side; (2) no seasonal sea-level effect at Los Angeles or at any point south of there down to the Straits of Magellan that is of sufficient magnitude to stand out above the fluctuations -- as much as 0.6 percent-observable at the different localities traversed in these voyages; (3) as heretofore on the voyage between Los Angeles and Vancouver, constancy in cosmic-ray intensity in summer and fall, within the limits of uncertainty imposed by the fluctuations, estimated here as certainly not over 1 percent; (4) in winter and spring, however, a definite increase in different voyages of 2 percent or 3 percent in going from Los Angeles to Vancouver. American Physical Society 1939-07 Article PeerReviewed application/pdf http://authors.library.caltech.edu/11133/1/MILrmp39.pdf http://resolver.caltech.edu/CaltechAUTHORS:MILrmp39 Millikan, R. A. and Neher, H. V. and Smith, D. O. (1939) Seasonal cosmic-ray effects at sea level. Reviews of Modern Physics, 11 (3-4). p. 166. ISSN 0034-6861 http://resolver.caltech.edu/CaltechAUTHORS:MILrmp39 <http://resolver.caltech.edu/CaltechAUTHORS:MILrmp39> http://authors.library.caltech.edu/11133/http://authors.library.caltech.edu/11133/1/