With Alexander was a group of men conventionally known as the bematists, or “pacers,” who accompanied his army engineers and surveyed the land routes traversed by his campaign (cf. Fraser 1996: 78ff). Pliny the Elder (HN 6.61–62) names Diognetos and Baiton as Alexander’s itinerum mensores and lists their land measurements for a long distance route from Media to India passing through the Caspian Gates, Hecatompylos, Alexandria in Areia, Prophthasia of the Drangoi, a city of the Arachosians, Hortospanus, Alexandria near the Hindu Kush, the Copheta river and Peucolaïtis, the Indus and Taxila, and finally the Hydaspes. He notes also that variant calculations existed for the stretch up to the Hindu Kush, presumably because more people were able to explore here than beyond it in the Indus region. Athenaeus (10.59) calls Baiton a bematist, also supplying the title of his text: Stathmoi tēs Alexandrou poreias (Stations of Alexander’s Expedition). Athenaeus (2.74, 10.59, 11.102, 12.9, and 12.39) mentions another bematist, Amyntas, whose work was titled Stathmoi or Stathmoi Persikoi. We know of another of Alexander’s pacers, Philonides, whose dedicatory inscription for his statue at Olympia lists him as “day-runner (hemerodromos) of king Alexander and bematist of Asia” (Inschriften von Olympia 276 and 277; Paus. 6.16.5). Philonides probably earned his statue for running across the Peloponnese from Sicyon to Elis, reported by Pliny (HN 2.181 and 7.84) as a distance of 1,305 stades, or approximately 149 miles (Matthew 1974: 165–166). That Philonides combined service as a courier and pacer recalls the extensive highway network used by the Persians for communicating across their empire. Aristotle (de mundo 398a) names hēmerodromoi among the servants of the king, and Herodotus (8.89) describes the impressive speed of the Persian couriers who relayed messages from station to station on horseback, a task requiring thorough knowledge of the terrain. Pliny (HN 6.63) hints that bematists continued in royal service after Alexander, reporting that Seleucus I, or rather anonymous people in his employ, completed the distances for India as far as the mouth of the Ganges. We also know of the general Patrokles, who explored the Caspian region for Seleucus I, and to whom geographies of Hycania and India are attributed (Pliny HN 6.58; FGrH 712; Müller FHG II, 442–444).
Units of Measurement
The titles of the bematists’ geographies were all apparently Stathmoi (Stations), indicating that they organized their data according to the stopping points along an itinerary. This had its basis in the practical needs of travelers, who needed to know how to schedule their journeys and arrange where to stay overnight. This was made possible by the many stathmoi, quite literally “stops,” way-stations, and caravanserais which dotted the old routes of the Persian Empire, spaced approximately a day’s travel apart and serving as watering holes, camp-sites, and courier depots. The bematists took measurements using the stadion (or stade) and stathmos, though the parasang and schoinos were also employed when dealing with pre-existing Persian distances. The stade was a well-known unit, used throughout Greece, and the stathmos came into use in the Hellenistic period when long overland journeys became more common. Neither unit was a fixed or exact measurement but varied according to region of use and topography of the route being measured. A stade is typically estimated as around 184 meters, for purposes of rough conversions into modern measurement units (except for Egyptian stades, which were shorter, like the Egyptian schoinos). A stathmos not only denoted the stopping point on a route, but also the distance traveled between two stops, hence it measured one day’s travel, variable depending on how heavily laden the travelers and their pack animals were. Herodotus (5.53) reports 111 stations on the Persian royal road from Sardis to Susa, which measured 13,500 stades, and, reckoning that a day’s journey was 150 stades, he reports that the total travel time along the road was 90 days.
Herodotus (2.6, 5.53) describes the Persian parasang measure as 30 stades and the Egyptian schoinos as 60; by his account the Sardis to Susa route was 450 parasangs. Xenophon (Anab. 2.2.6, 5.5.4, 7.8.26) also gives 30 stades for the parasang, although the passages in the Anabasis with his journey calculations hint at the parasang as either a variable unit of measure or one employed more for narratological impact than mathematical accuracy (Rood 2010). Strabo (11.11.5) puts the parasang at 40 stades, noting that it varied between 30 and 60 stades according to different authorities, and he gives the same length and variations for the schoinos. Strabo credits Artemidorus (not Herodotus) with the schoinos equivalency of 30 stades, based on his distance from Alexandria to the vertex of the Nile delta (28 schoinoi, or 840 stades), although he notes that he himself saw measures of 40 stades and more used for schoinoi on the Nile, where a schoinos denoted the interval between each of the cities, which were not equidistant (17.1.24, 11.11.5). The anonymous late ninth-century Byzantine Sylloge Tacticorum, preserved in a single codex (Laur. 75.6), contains a short passage on distance units. It states that the Persian parasang had a variable measure, from Xenophon’s 30 stades to 60 for others, as reported by Strabo in a quote from Posidonius (Edelstein and Kidd 1989, F203). It is suggested that this author, instead of directly consulting Strabo, took this material from other secondary sources on either Strabo or Posidonius’s scientific writings (Kidd 1988: 729–730).
Roman explorers measured in miles (milia passuum), and Strabo (Strabo 7.7.4; fr. 56 (Jones)) reported that most people counted eight stades to the mile, although Polybius (Polyb. 34.12.4) added an extra two plethra, or one-third of a stade, making eight and one-third stades equal to one Roman mile. Walbank suggested that Polybius’s amendment was for greater accuracy over long distances and easier mathematical conversions from miles to stades (Walbank 1979, iii. 624): to convert m.p. to stades one simply multiplies the distance by 25 and divides by 3. The Sylloge Tacticorum author also comments upon conversions to miles in Strabo, mistaking Polybius’s eight and one-third stades to the mile as a proposal of eight and one-quarter by Eratosthenes, and he asserts that the mile was now conventionally reckoned as seven and one-half stades, a calculation also appearing in Aelian’s Tactica (Kidd 1988: 730). Censorinus (de die nat. 13.2), who wrote in the first half of the third century CE, went so far as to call the stade that was one-eighth of a mile (625 Roman feet) the “Italic stade” (Morgan 1973: 30). Roman authors generally used stades when handling material taken from the Greek geographers or when dealing with nautical distances, and except for a few exceptional uses of the stade, they employed miles for all land measurements taken by Roman surveyors (Morgan 1973: 34–35; Arnaud 1993: 242).
Sea-Faring
The same method of measuring journeys by stops along a route was employed for sea travel recorded in the Periploi texts for the Phoenician and Arabian coasts. A Periplus was literally a “sailing around,” and was used as a title for several Greco-Roman texts giving the sailing distances around the Mediterranean sea, the Black Sea, and Indian Ocean. Sometimes the term paraplus, or “a sailing alongside,” is employed instead. Like Stathmoi texts, Periploi used a combination of distance units (based on variable sailing times as well as different measurement units, see Arnaud 1993: 231ff) and noted information about regions, cities, harbors, flora, fauna, commodities, and political curiosities along the routes described. Also like the land geographies, the Periploi were written to satisfy a number of different aims, some for practical application by navigators, others for more theoretical exercises. The earliest known Periplus is credited to Scylax of Caryanda, commissioned by Darius I to explore the Indus river and Indian Ocean.4 In the mid-fourth century BCE, an author now known as Pseudo-Scylax wrote a Periplus of the Mediterranean, which includes a description of the Syrian and Phoenician coast and so is a useful source for what was known of this region at the outset of the Hellenistic period (Müller, GGM I, xxxiii–li, 15–96). This text is wrongly attributed to Scylax of Caryanda (see Shipley 2011: 4–6), and it is now thought that it was not based on first-hand exploration, but worked more as philosophical geography. Alexander’s fleet-commander Nearchus and court historian Onesicritus wrote up accounts of their 326–325 BCE voyage from the Indus eastward to the Persian Gulf, which served as sources for Strabo and Pliny (HN 6.96,