39. In dealing with the part of Provence on the east side of the Rhone, Ptolemy (ii. 10. 7, 8) fixes Vienne as the city of the Allobriges; Valence as the city of the Segallauni; Orange, Avignon and Cavaillon as cities of the Cavari; and Vaison as the city of the Vocontii; and he places the Tricastini east of the Segallauni, north of the Vocontii and south of the Allobriges. He does not mention the Tricorii, but Strabo says (iv. 1. 11, 6. 5) that the Vocontii were “above” the Cavari, and the Tricorii “above” the Vocontii. The Tricorii would thus be east or north-east of Embrun, as he states (iv. 1. 3) that the territory of the Vocontii extended along the Durance up to Embrun. 40. Strabo says here (iv. 1. 3) that the Roman road from Tarascon to the Alps entered the territory of the Vocontii at “the beginning of the ascent,” 63 Roman miles from Tarascon and therefore near Mirabeau, and quitted it again at Embrun, 99 miles further on. And as he says here that the road ran along the Durance, and elsewhere (iv. 1. 11, cf. 6. 3, 4) treats the Durance as the frontier of the Salyes, the road might be described as running along the extreme edge of the territory of the Vocontii--_per extremam oram Vocontiorum agri_--which is the phrase employed by Livy (xxi. 31) for Hannibal’s line of march. The distances, the 63 and 99 miles, agree with what Polybios says of Hannibal’s march--see paragraph 29--and the digression would not be included in the distances he gives as marched “along the river,” iii. 39. 9, 50. 1. It would thus appear that after Hannibal had turned to the left into the territory of the Tricastini, he came back on to the line of what was afterwards the Roman road, and followed it from a point near Mirabeau to some point near Embrun. 41. Hannibal must have reached the Island the day after Scipio reached the crossing of the Rhone, as Polybios says (iii. 49. 1, 5) that Hannibal was four days on the march and had started from the crossing three days before Scipio got there. Polybios also says (iii. 49. 3, 4) that Scipio went back as fast as he came, re-embarked his forces and sailed off. Thus, by about the fifth day after Hannibal reached the Island, there was nothing to prevent his returning to the direct route to the Alps, supposing that he had quitted it in order to avoid a battle with the Romans. But this deviation, into the territory of the Tricastini, may really have been part of Hannibal’s movements in the civil-war in the Island, for Polybios says (iii. 49. 10) that Hannibal not only joined one faction in attacking the other, but joined in driving it out. As a matter of fact, Livy (xxi. 31) does not exactly say that Hannibal entered the territory of the Tricastini: he merely says _in Tricastinos_ and afterwards says _in Tricorios_, whereas in the intervening words, already quoted, he speaks of the “territory” of the Vocontii; and the difference may be more than merely verbal.