By amazing industry and a most rigid economy of time, Pliny combined with his continuous official duties an immense reading and a literary production of great scope and value. A hundred and sixty volumes of his extracts from writers of all kinds, written, we are told, on both sides of the paper in an extremely small hand, were bequeathed by him to his nephew. Besides works on grammar, rhetoric, military tactics, and other subjects, he wrote two important histories--one, in twenty books, on the wars on the German frontier, the other a general history of Rome in thirty-one books, from the accession of Nero to the joint triumph of Vespasian and Titus after the subjugation of the Jewish revolt. Both these valuable works are completely lost, nor is it possible to determine how far their substance reappears in Tacitus and Suetonius; the former, however, in both _Annals_ and _Histories_, repeatedly cites him as an authority. But we fortunately possess the most important of his works, the thirty-seven books of his _Natural History_. This is not, indeed, a great work of literature, though its style, while sometimes heavy and sometimes mannered, is on the whole plain, straightforward, and unpretentious; but it is a priceless storehouse of information on every branch of natural science as known to the ancient world. It was published with a dedication to Titus two years before Pliny's death, but continued during the rest of his life to receive his additions and corrections. It was compiled from a vast reading. Nearly five hundred authors (about a hundred and fifty Roman, the rest foreign) are cited in his catalogue of authorities. The plan of this great encyclopedia was carefully thought out before its composition was begun. It opens with a general system of physiography, and then passes successively to geography, anthropology, human physiology, zoology and comparative physiology, botany, including agriculture and horticulture, medicine, mineralogy, and the fine arts.