A few hours after flat racing's favorite, Kelso, had failed his fans at Laurel's International, harness racing's alltime champion, Adios Butler, made a memorable win of his farewell pace. Bidding adieu to competition in Roosevelt Raceway's $50,000 National Pacing Derby, the sport's fastest horse (No. 8) seemed for a moment to be threatened from the rear. Then Driver Eddie Cobb rattled the sulky shaft to remind the champion of his proud position, and the great pacer responded with a surge of speed. It carried him over the wire in time to match a track record and to set up a new total of $500,000 earned for his owners.