Because the term ""dirty old man"" has taken on new energy in the casual speech and patter of a nation quite taken by the Beatles' movie A Long Day's Night (Grandpa is always called a ""clean old man""), and by the Backporch Singers record, which has turned Ol' Dan Tucker into that ""mean ol', dirty ol' man,"" this title may make it as an impulse item in bookstores. The correctly applied, but nevertheless suggestive, subtitle is likely to help the devilish impulse along. Erik Blegvad has supplied small, delicate, full color miniatures of the dirty old man who might be the ancestor of Miss Havisham in Dickens' Great Expectations. The rhyme describes how he started out in life, gallant and spiffy, only to cascade into a decline when his lady love failed to show up for a dinner, which he kept untouched ever after. In the same vein as, but without the strength of, Galdone's recreation of juvenile recitation favorites.