4. _Historiae_.--The title is guaranteed by Tertull. _apol._ 16, 'Cornelius Tacitus in quinta historiarum suarum.' The work embraced the time from Galba to Domitian, _i.e._ 69-96 A.D. The first four Books and part of the fifth are extant, and give the history of 69 and most of 70 A.D. In MS. Mediceus II., the only ancient MS. that contains _Ann._ xi.-xvi. and the _Histories_, there is no title, but the Books are numbered continuously as belonging to the same work. Cf. Jerome, _Comm. on Zacharias_, iii. 14, 'Cornelius Tacitus, qui post Augustum usque ad mortem Domitiani vitas Caesarum triginta voluminibus exaravit.' If, therefore, the _Annals_ contained sixteen Books, the _Histories_ must have contained fourteen, supposing Jerome's statement to be correct. Some authorities think the numbers were eighteen and twelve respectively. The work was written under Trajan (cf. _Hist._ i. 1, 'principatum divi Nervae et imperium Traiani'), and was probably brought out in instalments. Pliny's letters (vi. 16; 20; vii. 33), written about A.D. 106-9, contain contributions to it.
5. _Annales_, or rather _Ab excessu divi Augusti_, the title given by MS. Med. I. Tacitus often calls his work _annales_ (as in _Ann._ iv. 32), but uses the word to signify his plan of recording events by their years. Cf. _Ann._ iv. 71, 'Ni mihi destinatum foret suum quaeque in annum referre, avebat animus antire,' etc.
He occasionally apologises (as in xii. 40) for departing from this order for the sake of clearness. The Books, the division into which was made by Tacitus himself (cf. vi. 27, 'in prioribus libris'), usually, however, end with some important event.
The _Annals_ deal with the time from the death of Augustus to that of Nero, _i.e._ from 14 to 68 A.D. There are extant Books i.-iv. and a part of v. and vi., and Books xi.-xvi., except the beginning of xi. and the end of xvi. We have thus lost the whole of the reign of Caligula and the reign of Claudius from 41-47 (part), and Nero's reign from the close of 66 to 68. The work was published between A.D. 115 and 117. This is settled by _Ann._ ii. 61, 'Exin ventum Elephantinen ac Syenen, claustra olim Romani imperii, quod nunc rubrum ad mare patescit.'