We learn from the preface that a measurement of the whole Roman world was ordered by Julius Caesar to be made by the most able men, that this measurement was begun in the consulship of Julius Caesar and M. Antonius, i. e. B. C. 44; that three Greeks were appointed for the purpose, Zenodoxus, Theodotus, and Polyclitus; that Zenodoxus measured all the eastern part, which occupied him twenty-one years, five months, and nine days, on to the third consulship of Augustus and Crassus; that Theodotus measured the northern part, which occupied him twenty-nine years, eight months, and ten days, on to the tenth consulship of Augustus; and that Polyclitus measured the southern part, which occupied him thirty-two years, one month, and ten days; that thus the whole (Roman) world was gone over by the measurers within thirty-two (?) years; and that a report of all it contained was laid before the senate. So it stands in the edd.; but the numbers are evidently much corrupted: the contradictoriness of Polyclitus's share taking more than 32 years, and the whole measurement being made in less than (intra) 32 years is obvious.

It is to be observed that, in this introductory statement, no mention is made of the western part (which in the work itself comes next to the eastern), except in the Vatican MS., where the eastern part is given to Nicodomus, and the western to Didymus.

A census of all the people in the Roman subjection was held under Augustus. (Suidas, s. v. Αὔγουστος.) By two late writers (Cassiodorus, Var. 3.52, by an emendation of Huschke, p. 6, über den zur Zeit der Geburt Jesu Christi gehaltenen Census, Breslau, 1840; and Isidorus, Orig. 5.36.4), this numbering of the people is spoken of as connected with the measurement of the land. This work in fact consists of two separate pieces. The first begins with a short introduction, the substance of which has been given, and then proceeds with an account of the measurement of the Roman world under four heads, Orientalis, Occidentalis, Septentrionalis, Meridiana pars. Then come series of lists of names, arranged under heads, Maria, Insulae, Montes, Provinciae, Oppida, Flumina, and Gentes. These are hare lists, excepting that the rivers have an account of their rise, course, and length annexed. This is the end of the first part, the Expositio. The second part is called Alia totius orbis Descriptio, and consists of four divisions: (1.) Asiae Provinciae situs cum limitibus et populis suis; (2.) Europae situs, &c.; (3.) Africae situs, &c.; (4.) Insulae Nostri Maris. This part, the Description, occurs with slight varia tions in Orosins, 1.2. In Aethicus what looks like the original commencement, Majores nostri. &c., 16 tacked on to the preceding part, the Expositio, by the words Hanc quadripartitam totius terrae continentiam hi qui dimcnsi sunt. From this it would appear that Aethicus borrowed it from Orosius.

The work abounds in errors. Sometimes the same name occurs in different lists; as, for example, Cyprus and Rhodes both in the north and in the east; Corsica both in the west and in the south; or a country is put as a town, as Arabia; Noricum is put among the islands. Mistakes of this kind would easily be made in copying lists, especially if in double columns. But from other reasons and from quotations given by Dicuil, a writer of the 9th century, from the Cosmographia, differing from the text as we have it, the whole appears to be very corrupt. The whole is a very meagre production, but presents a few valuable points. Many successful emendations have been made by Salmasius in his Exercitationes Philologicae, and there is a very valuable essay on the whole subject by Ritschl in the (1842), 1.4.

The sources of the Cosmographia appear to have been the measurements above described, other official lists and documents, and also, in all probability, Agrippa's Commentarii, which are constantly referred to by Pliny (Hist. Nat. iii. iv. v. vi.) as an authority, and his Chart of the World, which was founded on his Commentarii. (Plin. Hist. Nat. 3.2.)

Cassiodorus (de instit. divin. 25) describes a cosmographical work by Julius Honorius Crator in terms which suit exactly the work of Aethicus; and Salmasius regards Julius Honorius as the real author of this work, to which opinion Ritschl seems to lean, reading Ethnicus instead of Aethicus, and considering it as a mere appellative. In some MSS. the appellatives Sophista and Philosophus are found.