Athelstan F. Spilhaus, 86, geophysicist and first U.S. ambassador to the United Nations Educational, Scientific and Cultural Organization (UNESCO). A native of Cape Town, South Africa, Spilhaus was educated at the University of Cape Town and the Massachusetts Institute of Technology. He was named to the UNESCO post by President Dwight D. Eisenhower in 1954 and served in other scientific posts during the Kennedy and Johnson administrations. Link created the U.S. science exhibit at the 1962 Seattle World's Fair. He also developed the bathythermograph to measure temperatures in the deep ocean and proposed the national Sea Grant program in 1963. When he was dean of the University of Minnesota's Institute of Technology, Spilhaus developed covered skyways and tunnels to connect buildings in Minneapolis and other areas subject to severe weather. On Monday in Middleburg, Va.