Four years later a fourth book of _Odes_ was published, the greater part of which consists of poems less distinctly official than the _Secular Hymn,_ but written with reference to public affairs by the direct command of the Emperor, some in celebration of the victories of Drusus and Tiberius on the north-eastern frontier, and others in more general praise of the peace and external prosperity established throughout Italy under the new government. Together with these official pieces he included some others: an early sketch for the _Carmen Seculare,_ a curious fragment of literary criticism in the form of an ode addressed to one of the young aristocrats who followed the fashion of the Augustan age in studying and writing poetry, and eight pieces of the same kind as his earlier odes, written at various times within the ten years which had now passed since the publication of the first three books. An introductory poem, of graceful but half-ironical lamentation over the passing of youth, seems placed at the head of the little collection in studious depreciation of its importance. Had it not been for the necessity of publishing the official odes, it is probable enough that Horace would have left these few later lyrics ungathered. They show the same care and finish in workmanship as the rest, but there is a certain loss of brilliance; except one ode of mellow and refined beauty, the famous _Diffugere nives,_ they hardly reach the old level. The creative impulse in Horace had never been very powerful or copious; with growing years he became less interested in the achievement of literary artifice, and turned more completely to his other great field, the criticism of life and literature. To the concluding years of his life belong the three delightful essays in verse which complete the list of his works. Two of these, which are placed together as a second book of _Epistles_, seem to have been published at about the same time as the fourth book of the _Odes_. The first, addressed to the Emperor, contains the most matured and complete expression of his views on Latin poetry, and is in great measure a vindication of the poetry of his own age against the school which, partly from literary and partly from political motives, persisted in giving a preference to that of the earlier Republic. In the second, inscribed to one of his younger friends belonging to the circle of Tiberius, he reviews his own life as one who was now done with literature and literary fame, and was giving himself up to the pursuit of wisdom. The melancholy of temperament and advancing age is subtly interwoven in his final words with the urbane humour and strong sense that had been his companions through life:-- _Lusisti satis, edisti satis atque bibisti, Tempus abire tibi est, ne potum largius acquo Rideat et pulset lasciva decentius aetas._