366 LIST ET AL, Fig. 7—Strontium-90 in soil in 1963 and early 1964 in the continental United States and southern Canada, millicuries per square mile, on the western side of the Wasatch Mountains, is more than twice as great as that found at Logan, Utah, about 70 miles to the north but on the eastern slopes of the mountain range. The discrepancy between the values at Salt Lake City and at Logan suggested that a more complete investigation in the vicinity of the Great Salt Lake was in order. It was originally suggested that the very high deposition at Salt Lake City was somehow connected with its position relative to the Nevada TestSite. In 1962 additional samples on the east and west sides of the Wasatch Mountains were obtained.* The stations on the western, or lake, side of the mountains showed ™Sr deposition values about -twice those on the eastern side. Another sampling in 1963 in the southwestern corner of Utah and very much closer to the Nevada Test Site showed values comparable to those on the eastern side of the Wasatch Mountains. This led to the conclusion that the high values at Salt Lake City were related to the proximity to the Great Salt Lake or to surrounding salt deserts. Although no complete physical explanation of the phenomenon has been advanced, presumably it is related to the abundance of salt nuclei in the air. It is interesting to note that the total Sr deposition reported for the HASL ion-exchange column at Salt Lake City for the 1960 to 1963 period compares very closely with the deposition occurring in Salt Lake City soils during the same period. Another, much larger area of high Sr deposition is in the central and northern Great Plains states. There have been several attempts