Vincent adopted the opinion of Salmasius regarding the date of the work, but thinks that the Kaîsar mentioned in § 26 was Claudius. “The Romans,” he says, “from the time they first entered Arabia under Ælius Gallus, had always maintained a footing on the coast of the Red Sea. They had a garrison at +Leukê Kômê+, in Nabathaea, where they collected the customs; and it is apparent that they extended their power down the gulf and to the ports of the ocean in the reign of Claudius, as the freedman of +Annius Plocamus+ was in the act of collecting the tributes there when he was carried out to sea and over to +Taprobanê+. If we add to this the discovery of Hippalus in the same reign, we find a better reason for the destruction of Aden at this time than at any other.” The assertion in this extract that the garrison and custom-house at +Leukê Kômê+ belonged to the Romans is not warranted by the language of the _Periplûs_, which in fact shows that they belonged to +Malikhos+ the king of the Nabathæans. Again, it is a mere conjecture that the voyage which the freedman of Plocamus (who, according to Pliny, farmed the revenues of the Red Sea) was making along the coast of Arabia, when he was carried away by the monsoon to Taprobanê, was a voyage undertaken to collect the revenues due to the Roman treasury. With regard to the word Καῖσαρ, which has occasioned so much perplexity, it is most probably a corrupt reading in a text notorious for its corruptness. The proper reading may perhaps be ΕΛΙΣΑΡ. At any rate, had one of the emperors in reality destroyed Aden, it is unlikely that their historians would have failed to mention such an important fact. Schwanbeck, although he saw the weakness of the arguments with which Salmasius and Vincent endeavoured to establish their position, nevertheless thought that our author lived in the age of Pliny and wrote a little before him, because those particulars regarding the Indian navigation which Pliny says became known in his age agree, on the whole, so well with the statement in the _Periplûs_ that they must have been extracted therefrom. No doubt there are, he allows, some discrepancies; but those, he thinks, may be ascribed to the haste or negligence of the copyist. A careful examination, however, of parallel passages in Pliny and the _Periplûs_ show this assertion to be untenable. Vincent himself speaks with caution on this point:—“There is,” he says, “no absolute proof that either copied from the other. But those who are acquainted with Pliny’s methods of abbreviation would much rather conclude, if one must be a copyist, that his title to this office is the clearest.”