During July, August, and September of 1974, daily aerosol measurements were made at three stations in the tropical North Atlantic: Sal Island, Cape Verde islands; Barbados, West Indies; Miami, Florida. The two major components of the aerosols at each station were mineral aerosol, comprising Saharan dust, and sea salt. Fifty-eight samples were analyzed to determine the atmospheric concentrations of water-soluble sodium, potassium, magnesium, and calcium and of the mineral aerosol. By using a multiple variable regression technique, the dominant source of water-soluble potassium was found to be sea salt; the Saharan dust did, however, contribute a significant and sometimes quite substantial fraction (up to 38%). The soluble magnesium was almost exclusively a consequence of the presence of sea salt aerosols. In contrast, the soluble calcium at Sal Island and Barbados was derived predominantly (~80%) from the Saharan dust; at Miami the contribution from Saharan aerosols (~50%) and locally generated soil aerosols (~40%) dominated the sea salt aerosol with respect to the amount of soluble calcium contributed. In comparison to the global continent-to-ocean flux via streams, the flux of soluble potassium via the atmosphere is probably negligible; the flux of soluble calcium via the atmosphere, however, may be of the order of 10% of that via streams.