If Music be, among the arts, 'Heaven's youngest-teemed star', the latest of the art-forms she herself has brought forth is unquestionably Opera. Three hundred years does not at first seem a very short time, but it is not long when it covers the whole period of the inception, development, and what certainly looks like the decadence, of an important branch of man's artistic industry. The art of painting has taken at least twice as long to develop; yet the three centuries from Monteverde to Debussy cover as great a distance as that which separates Cimabue from Degas. In operatic history, revolutions, which in other arts have not been accomplished in several generations, have got themselves completed, and indeed almost forgotten, in the course of a few years. Twenty-five years ago, for example, Wagner's maturer works were regarded, by the more charitable of those who did not admire them, as intelligible only to the few enthusiasts who had devoted years of study to the unravelling of their mysteries; the w