Never make people laugh...All great monuments are built over solemn asses."" This was the advice offered by Sen. Thomas Corwin to Presidential candidate Garfield and, although there have been grand exceptions to his rule, it seems to work in a majority of political cases. Among the grand exceptions here are Richard Brinsley Sheridan, who lived up to what Harris calls the mid-wife's phrase for wit -- ""A quick conception and an easy delivery."" The author's essay contrasting British and American practice points up the fact of our national predilection for anecdotal humor while the British employ a more literary wit. John Randolph of Roanoke and Aneurin Bevan emerge as the masters of inventive. The elegant insults of Disraeli and the repartee of Lloyd-George overshadow our F.D.R., whom associates claim was prone to enjoy non-creative sarcasm. Of course there is a long section of Churchill at his quotable best and a patchwork of Adlai Stevenson's polished impromptus. It ends with John F. Kennedy, whom Harris calls the leader of ""a considerable renaissance of wit in American politics."" Altogether, it's rousing good browsing.