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Bematist
From Wikipedia, the free encyclopedia
Bematists were specialists in ancient Greece who were trained to measure distances by counting their steps.
Bematists accompanied Alexander the Great on his campaign in Asia. Their measurements of the distances traveled by Alexander's army show a high degree of precision to the point that it had been suggested that they must have used an odometer, although there is no direct mentioning of such a device:
- The overall accuracy of the bematists’ measurements should be apparent. The minor discrepancies of distance can be adequately explained by slight changes in the tracks of roads during the last 2,300 years. The accuracy of the measurements implies that the bematists used a sophisticated mechanical device for measuring distances, undoubtedly an odometer such as describes by Heron of Alexandria.[1]
The table below lists distances of the routes as measured by two of Alexander's bematists, Diognetus and Baeton. They were recorded in Pliny's Naturalis Historia (NH 6.61-62). Another similar set of measurements is given by Strabo (11.8.9) following Eratosthenes.[2]
| Pliny 6.61-62 | Strabo 11.8.9 | Actual Distance | |||||
|---|---|---|---|---|---|---|---|
| Route | Milia passum 1) | English Miles | Deviation | Stadia 2) | English Miles | Deviation | English Miles |
| Northern Caspian Gates - Hecatompylos | 3) | 1960 | 225 | 0.8% | 227 main road | ||
| Southern Caspian Gates - Hecatompylos | 133 | 122 | 2.4% | 125 main road | |||
| Hecatompylos – Alexandria Areion | 575 | 529 | 0.4% | 4530 | 521 | 1.9% | 531 Silk Route |
| Alexandria Areion – Prophtasia | 199 | 183 | 3.2% | 1600 | 184 | 2.6% | 189 Herat-Juwain |
| Prophtasia – Arachoti Polis | 565 | 520 | 1% | 4120 | 474 | 9.7% | 525 Juwain – Kelat-i-Ghilzai |
| Arachoti Polis – Hortospana | 250 | 230 | 0.4% | 2000 | 230 | 0.4% | 231 main road Kelat-i-Ghilzai – Kabul |
| Hortospana – Alexandria ad Caucasum | 50 | 46 | 2.1% | 47 Kabul – Begram | |||
| Alexandria ad Caucasum - Peucolatis | 237 | 218 | 3.2% | 211 Begram – Charsada | |||
| Peucolatis - Taxila | 60 | 55 | 20% | 69 Charsada – Taxila | |||
| Taxila – Hydaspes (Jhelum) | 120 | 110 | 4.8% | 105 Aurel Stein’s route | |||
| Alexandria Areion – Bactra – Zariaspa4) | 3870 | 445 | 1.6% | 438 via Kala Nau, Bala Murghab, Maimana and Andkhui | |||
| Average | 4.2% | 2.8% | |||||
| Median | 2.8% | 1.9% | |||||
Notes:
1) 1 mille passus = 1,480 meters or 1618.5 yards
2) 1 Attic stadion = 606’10’’
3) No entries: Data not specified (n.s.)
4) The route is not recorded to have been followed by Alexander himself.
Addenda: Leaving out the highest outlier each, the average deviation of the rest of the bematists's measurements would be 1.9% with Pliny and 1.5% with Strabo at a measured distance of 1958 respectively 1605 miles.