Clyde Wahrhaftig, 74, a geologist with the U.S. Department of the Interior and author of several geological guidebooks to western cities, among them San Francisco. Wahrhaftig never learned to drive and based his published tours of geologic attractions on access by bus and streetcar. A graduate of Caltech and Harvard University, he started with the Interior Department's Geological Survey in 1941, mapping the coastal basins of Santa Barbara before moving to Alaska for fieldwork. In 1945, he was among the first group of scientists posted to Hiroshima and Nagasaki to study the effects of nuclear bombing. In 1960, he became a professor of geology at UC Berkeley while continuing to work for the Geological Survey. In San Francisco on Friday of unreported causes.