Humor doesn't travel very well, especially from the telling to the printed page. In this survey of radio humor, some of the medium's most memorable jokes lie parched and dusty, leaving even a reader who heard them the first time around to wonder why they were ever considered funny. It is this ephemeral and fragile quality of comedy--plus the advent of television--that spelled the demise of the radio comedian. The author, a history professor, recalls rather pedantically the short, brilliant history of the famous jokesmiths, from Amos 'n' Andy in the late Thirties to ""The Charlie McCarthy Show"" of 1956, for which CBS could not find a sponsor. By that time, most of the major stars--Jack Benny, Bob Hope, Red Skelton--had made a successful transition to TV. Along the way, we are introduced to the early performers--Easy Aces, Fibber McGee and Molly, Burns and Allen, Vic and Sade--and to such radio novae as Joe Penner, Jack Pearl, and Stoopnagle and Budd, along with the revered Fred Allen. Professor Wertheim offers thumbnail sketches of the major stars as well as samples of their sketch material, but his most useful service is in tracing the way radio comedy, which was relentlessly aimed at the middle class, changed and developed with such social phenomena as the Depression and World War II. But there is not much humor here. Once a joke has been explained, put in its proper social context, its teller profiled and a footnote appended, the inclination to laughter is stifled.