Isaac Mitton Stewart, 13-year president of the Mormon Tabernacle Choir during the 1960s and '70s, died Friday, Dec. 14, 1990, at his Indian Wells, Calif., home. He was 85.

Mr. Stewart's long life was dedicated to public service. A graduate ofthe University of California, Los Angeles, Mr. Stewart received his law degree from George Washington University in 1928 before serving as an assistant to Sen. Reed Smoot from 1928-1932.

Mr. Stewart later practiced law in Washington, D.C., and was involved in the development of the atomic bomb during the Manhattan Project. He was president of Union Carbide Corp. from 1949-1967 and director of Consolidated Freightways from 1958-1983. During 1983-1984, Mr. Stewart was a consultant to Bonneville International.

Called to serve as president of the Tabernacle Choir in October 1962, Mr. Stewart succeeded Lester F. Hewlett. He retired from this position in August 1975 for health reasons.

During his long career, Mr. Stewart was also one of the first official observers to the United Nations for The Church of Jesus Christ of Latter-Day Saints. He served as a member of the U.S. Senate Advisory Committee on Interstate and Foreign Commerce and received the George Washington University Distinguished Alumni Award in Law and Public Service.

Services will be held in California on Monday, and he will be buried in the Francis Cemetery, Francis, Summit County.

The family asks that remembrances be donations to the Cystic Fibrosis Research Foundation, 2323 N. Mayfair Road L-23, Milwaukee, WI 53226.