IAMBIC, a verse or succession of verses composed wholly or principally of the foot called an iambus (v ) . It is generally described by a compound name consisting of a Greek numeral and the word metron, signifying a group of two iambi; as, iambic dimeter, a line consisting of two metra or four iambi: "perunxit hoc Iasonem," or "John Gilpin was I a citizen." The commonest form, and one of the most popular of Greek metres, especially in drama, is the trimeter (three metro, or six iambi). When "pure," i.e., containing no other feet, this runs "suis et ipsa Roma viribus ruit." But as a substitute for each of the first five iambi, under various restrictions more or less severe according to subject and language, the ancients allowed a spondee (- -), a tribrach (.. .), a dactyl ( an anapaest (s v -), sometimes a proceleusmatic (? ), Other common lines are the tetrameter catalectic ("paratus omne V v V ... v v v -, Caesaris periculum subire") and acatalectic ("beatus ille qui procul negotiis, ut prisca gens"), with similar substitutions al lowed. These last two are common in English, as "In good King Charlesi's golden days, I when loyalty I no harm I meant," and "But come, thou god' dess fair I and free, I in heaven I yclept Euphrosyne," but the trimeter is almost unknown; Spenser's "Unhappy verse I the witness of I my unhappy state" is an ex ample; the Alexandrine, as "And hope to merit Heaven I by making earth a hell," has a different rhythm. Its place in our literature is taken by the five-foot line, in couplets or "blank," as "A lit!tie on I ward lend I thy gui ding hand."