along the Arabian coast, including Androsthenes of Thasos, who had also traveled with Nearchus and wrote Periplus of the Indian Coast, a source used by Eratosthenes and Athenaeus (Strabo 16.3.2; Athen. 3.93b; FGrH 711; Wirth, “Androsthenes 4,” Der Kleine Pauly, 350–351; Potts 1990: 5). Other reports from sea expeditions sent by Alexander and the Ptolemies informed the historian and geographer Agatharchides of Cnidus (c. 200–c. 145 BCE) who wrote On the Erythraean Sea, known from excerpts in Diodorus Siculus (3.12–48), Strabo (16.5.5–20), and Photius (Bibliotheca Codex 250) (FGrH 86, Müller, GGM I, liv–lxxiii, 111–194; Burstein 1989: 30–32, 176ff).
In the second century BCE the Greeks learned about the monsoon winds, what they called the etesian (annual) winds, which permitted long-distance open-sea travel to India at certain times of year. Strabo (2.3.4) seems to report an early discovery of the monsoons in his account of the hapless Eudoxus of Cyzicus who made two voyages across the Indian Ocean for Ptolemy Physcon and Cleopatra III in c. 117–116 BCE, while the author of the Periplus Maris Erythraei (dated to the mid-first century CE based on a reference to Malichus II of Nabataea, r. 40–70 CE) credits a fellow sea-captain named Hippalos. It is possible that both attributions are correct and that other Hellenistic sea-farers independently noticed the phenomenon, but Strabo obtained his reference for the winds from a text, in this case Posidonius’s history of Eudoxus’s misadventures.5 Using the monsoons correctly, later travelers were able to venture much farther beyond the Persian Gulf and Arabia, although the Arabian frankincense trade ensured that Near Eastern ports remained important. The most complete Periplus text is the Periplus Maris Erythraei, preserved in a tenth-century codex (Codex Palatinus Graecus 398, fol. 40v–54v), written by an Egyptian Greek merchant from his personal experiences sailing out of the Red Sea at least as far as Rhapta (near Dar es-Salaam, Tanzania) and Cape Comorin, India.6 He meticulously reports the distances between stops, types of anchorage available at each stop, the local political situations, and what commodities can be acquired and offloaded. Much later, Marcianus of Heraclea (1.15–19) converted Ptolemy’s world map into a Periplus of the Outer Sea, supplying similar accounts of the Arabian and Persian Gulfs as the earlier Periploi authors, but within a global scheme (Schoff 1927: 6).
The Roman Period
The imperial ambitions motivating geographical research begun under the Hellenistic rulers continued under Augustus after he had firmly established Roman dominance in the Near East, and M. Vipsanius Agrippa was the major authority, serving as governor in Syria and leading a number of campaigns there. He oversaw production of a world map at Rome in the Porticus Vipsania, still incomplete at his death in 12 BCE, and several accompanying commentaries (Dilke 1985: 41–42, 1987: 207–209; Nicolet 1991: 98ff; Pliny HN 3.17). Pliny the Elder quotes Agrippa at several points in his Natural History, generally referring to the commentaries, and in a few instances to the map itself. For example, the dimensions of Mesopotamia (800 miles long, 360 miles wide) come from the commentaries (HN 6.137), while the distance of Charax Spasinou (an old Hellenistic city located at the confluence of the Tigris and Eulaeus rivers7 ) to the Persian Gulf is obtained from the map “Agrippa’s portico” (HN 6.139; cf. Dilke 1985: 50). Around 1 BCE, preparatory to an expedition by Gaius Caesar, Juba of Mauretania and Isidorus of Charax were commissioned to prepare surveys of Parthia and Arabia, the results of which augmented Agrippa’s earlier information (Pliny HN 6.141).8 Isidorus’s description of Parthia contains hints that it was indeed intended for a military force, as with its reference to an army crossing the Euphrates at the confluence of the Khabur river north of Dura-Europos: Isidorus says (FGrH 781 F2 §1) “there the army crosses over to the Roman side,” i.e. from the east bank to the west (Millar 1998a: 120).
Juba was a historian, ethnographer, and client king of the Romans, and he concentrated his report On Arabia for Gaius Caesar on southern Mesopotamia, Arabia, and the coasts of the Persian Gulf and Red Sea, now known through Pliny the Elder’s Natural History (FGrH 275, especially F1–3, 30–34). Isidorus’s report, Parthian Stations (Stathmoi Parthikoi), is possibly the summary of a longer description, the Guidebook of Parthia (Parthias Periēgētikon) (Schoff 1914: 17).9 It is preserved in the late thirteenth-century Codex Parisinus suppl. gr. 443 and Codex Parisinus gr. 571 (Diller 1952: 19–20, 30; 46–4710 ) and like the bematists’ writings it describes the route and stations for a west-to-east journey. Isidorus reveals the continuity of Persian routes and stations and the eastern Hellenistic cities up to the first century CE, as well as the current geopolitical situation. Of the regions surveyed, he describes Mesopotamia in the greatest detail, tracing a route from Zeugma down the east side of the Euphrates through Anthemousia to Ichnai and Nikephorion, back across the Euphrates, down its west bank to Dura-Europos, and weaving across the river valley to Seleucia on the Tigris. In mapping this particular route Isidorus revealed to his Roman patrons the ramifications of new Parthian dominance in the Euphrates valley. Isidorus’s contemporary Strabo, writing only a decade or so earlier, represents an earlier situation in his description (16.1.27–28) of a very different highway across the desert, taken by merchants enjoying friendship with the desert nomads and wishing to avoid the higher tariffs exacted by local chieftains controlling the Euphrates river valley. By Isidorus’s time of writing the Parthians had enforced use of the older and longer Hellenistic route around the Fertile Crescent, so as to collect the tolls, an important source of income for their empire (Gawlikowski 1994: 27, 31). When Strabo produced a revised edition of his Geography around 18 CE he did not update the Parthian material (Roseman 2005: 28 n.9): Strabo’s first edition appeared in 7 BCE, and a revised edition in 18 CE, and he did not use Agrippa’s map as evidence, which fits with the earlier date since the map was not finished in 7 BCE.
Isidorus gives detailed information for the routes and stations across Mesopotamia and Babylonia as far as the Tigris, observing the locations and names of villages and cities (always called poleis), and noting where there are royal stathmoi, as at the fortress Alagma near Ichnai and at Thillada Mirrada, and which cities are Greek, namely Anthemousia, Ichnai, Nikephorion, Dura-Europos (FGrH 781 F2 §1). Beyond Seleucia on the Tigris were two relatively densely populated regions, Apolloniatis and Chalonitis, with a noticeable Greek presence, so they also receive more attention. Isidorus describes both as containing a number of villages and Greek (Artemita and Chala) and non-Greek (Chalasar) cities (FGrH 781 F2 §§2–3). Once into Media, the route stretches out over longer distances, with fewer cities and villages mentioned; Isidorus continues to name the cities, some of which are Greek, and indicates the presence of stathmoi, but few of his western audience can have expected to venture this far. Indeed we may wonder how much of this route Isidorus himself traveled (cf. Fraser 1996: 91–92). The key to understanding Isidorus’s text, as with all the Greco-Roman geographies, is to consider its purpose. Isidorus conducted his survey of Parthia for political reasons, not scientific, and so he focuses upon cities, structures, and terrain of significance to the Augustan leadership, enumerating the Greek cities still flourishing under Parthian rule, the location of fortresses and “royal” stathmoi (presumably large enough to furnish a rest stop for an army or expeditionary force), and the disposition of civilian habitations and strategic river crossings (Millar 1998a: 120–121). All of these are what a Roman contingent would need to know in order to gather local intelligence effectively and manage their encounters with Parthian forces.
We know from Pliny (HN 5.83, 6.40) that Domitius Corbulo’s expedition to Armenia for Nero produced some new measurements for the upper Euphrates and Caspian region. For evidence of later expeditions and geographic surveys during the resurgence of Roman campaigns against the Parthians under Trajan and Hadrian, the main source is Ptolemy’s Geographikē hyphēgēsis (or, Guide to Drawing the World, conventionally titled Geography) (Berggren and Jones 2000: 4). We have the name of one Syrian, Maes Titianus, who ventured along the Silk Road as far as the Stone Tower (Tashkurgan, Xinjiang) and supplied Ptolemy with 876 schoinoi (26,280 stades) as the land distance from the Euphrates to Stone Tower (Ptol. Geog. 1.11.3). Maes sought to trade directly with the Chinese silk merchants whose wares normally passed to the avid Roman market via Parthian traders