[Sidenote: The Natural History.] The result of Pliny’s diligence is seen in his great encyclopædic work, the _Natural History_, in thirty-seven books. In this he undertakes to describe the whole realm of nature in a systematic way. The first book consists of a table of contents with a list of the authors consulted. Then follow in order the general mathematical and physical description of the universe, geography and ethnology, anthropology, zoology, botany, and mineralogy. Under mineralogy the uses of metals and stones are described, and this leads to a valuable history of painting and sculpture. The _Natural History_ is written for the most part in a simple, straightforward style, though with occasional lapses from good taste, but it is not a great work of literature. Its importance lies in the information it contains. In the first book, Pliny mentions nearly five hundred authors from whom his information is derived, but as he also speaks of one hundred chosen ones whose works he consulted, it is evident that his authorities fall into two classes. Apparently he really consulted about one hundred, but recorded in the first book the names of other writers to whom his real authorities referred. Pliny is almost the only ancient writer who tries to give much information about the sources of his knowledge, but it is often difficult, if not impossible, even in his case to be sure from what source a particular statement is derived. In general, it is clear that Pliny was a careful worker, and his statements can, as a rule, be accepted as true. The great work was ready for publication in 77 A. D. and was sent to Titus with an interesting preface. But even after this, Pliny continued to add the results of further reading or observation. His death came upon him in the midst of his work. [Sidenote: Pliny’s other works.] Pliny was also the author of several other works, the most important of which were the _History of the German Wars_, in twenty books, and a history _From the End of the History of Aufidius Bassus_, in thirty-one books. Just what period this work embraced is not certain, but the suggestion that each book treated of one year and that the whole was a history of the years 41-71 A. D. is not improbable. These works, as well as Pliny’s lesser writings, are lost, but they served at least to supply material to Tacitus, who cites the _German Wars_, and to other historians.