Diagram showing climatic zones.

Aristotle, on the other hand, divided the Earth into five zones, assuming two frigid climes (the arctic and antarctic) around the poles, an uninhabitable torrid clime near the equator, and two temperate climes between the frigid and the torrid ones (Meteorology 2.5,362a32).

Ptolemy

Ptolemy gives a list of parallels, starting with the equator, and proceeding north at intervals, chosen so that the longest day (summer solstice) increases in steps of a quarter of an hour from 12 hours at the equator to 18 hours at 58° N, and then, in larger steps, to 24 hours at the arctic circle.

But for the purposes of his geographical tables, Ptolemy reduces this list to eleven parallels, dividing the area between the equator and 54°1' N into ten segments, at half-hour intervals reaching from 12 hours to 17 hours. Even later in his work, he reduces this to seven parallels, reaching from 16°27' N (13 hours) to 48°32' N (16 hours).

In reducing his original system, informed by the spherical shape of the earth, into seven climes, Ptolemy was thus trying to reconcile his work with the geographical tradition of seven klimata. This division in seven zones may go back to notions of geography predating the idea of a spherical Earth introduced by Pythagoras in the 6th century BC. Persian tradition knows seven karshvar (Modern Persian keshvar) or zones, organizing the world map into a seven-storied ziggurat.

Maybe for this reason, Ptolemy's system of seven climes was primarily adopted by Arab and Persian authors such as al-Burini, al-Idrisi and Amin Razi, the author of the 16th century haft iql?m (seven climes), while in Europe, Aristotle's system of five climatic zones was more successful. This view dominated in medieval Europe, and existence and inhabitability of the Southern temperate zone, the antipodes, was a matter of dispute.

To identify the parallels delineating his climes, Ptolemy gives a geographical location through which they pass. The following is a list of the 33 parallels of the full system of climes, the reduced system of seven climes is indicated by additional numbers in brackets (note that the latitudes are the ones given by Ptolemy, not the modern exact values):

1. 12:00 (equator)
2. 12:15, 4°4' N: Taprobana (Sri Lanka)
3. 12:30, 8°25' N: Avalite bay (Saylac, Somalia)
4. 12:45 12°00' N: bay of Adulis (Eritrea)
5. (1.) 13:00, 16°27' N: Meroe island
6. 13:15, 20°14' N: Napaton (Sudan)
7. (2.) 13:30, 23°51' N: Soene (Aswan)
8. 13:45, 27°12' N: Thebes
9. (3.) 14:00, 30°22' N: Lower Egypt
10. 14:15, 33°18' N: Phoenicia
11. (4.) 14:30, 36°00' N: Rhodes
12. 14:45, 38°35' N: Smyrna
13. (5.) 15:00, 40°50' N: Hellespont
14. 15:15, 43°04' N: Massalia (Marseilles)
15. (6.) 15:30, 45°01' N: the middle of the Black Sea
16. 15:45, 46°51' N: Istros river
17. (7.) 16:00, 48°32' N: the mouths of Borysthenes (Dnepr)
18. 16:15, 50°04' N: Maiotian lake
19. 16:30, 51°06' N: the southern shore of Britannia
20. 16:45, 52°50' N: mouths of the Rhine
21. 17:00, 54°30' N: mouths of the Tanais river (Don)
22. 17:15, 55° N: Brigantion in Britannia
23. 17:30, 56° N: the middle of Great Britain
24. 17:45, 57° N: Katouraktonion in Britannia
25. 18:00, 58° N: the southern part of Britannia Minor
26. 18:30, 59° N: the middle part of Britannia Minor
27. 19:00, 61° N: the North of Britannia Minor
28. 19:30, 62° N: Ebudes island
29. 20:00, 63° N: Thule (Iceland)
30. 21:00, 64° N: unknown "Scythian people"[?]
31. 22:00, 65° N
32. 23:00, 66° N
33. 24:00, 66°08'40'' N: the polar circle

See also

• Climate
• Seven Seas

References

• J. Lennart Berggren and Alexander Jones, Ptolemy's Geography: An Annotated Translation of the Theoretical Chapters, Princeton University Press (2000).
• The Itinerary of Alexander through the Seven Climes of Antiquity according to the Aljamiado-Morisco Rrekontamiento del rrey Alisandre. Santa Barbara, CA. Fifth Annual Middle East Studies Regional Conference. March 22, 2003.

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