Some book nut in a dusty Buy-Old-Volumes-by-the-Pound warehouse on some obscure Fourth Avenue of the future, in say 40 years or so, will come across a battered copy of "Heartland" and, leafing through a few pages, will wonder just who the hell this Mort Sahl was. Well, anyone who was slugging it out in the entertainment world of the middle 50's and early 60's would certainly know. When I first started my own career as a humorist, paying customers would come up to me after the show in nightclubs in Cincinnati or Philadelphia and ask me, "Have you heard this guy Sahl?" He almost immediately thereafter became the hot-test thing in the business, toasted by Presidential candidates, movie queens, and even Paul Newman. Ponderous old Henry Luce put him on the cover of Time, which in those days was about like being canonized. He was forever enshrined among the hallowed greats of history along with Chiang Kai-shek and Thomas E. Dewey.