Clime

The seven climes (klima, plural klimata, meaning "inclination", referring to the angle between the axis of the celestial sphere and the horizon) was a notion of dividing the Earth into zones in Classical Antiquity. The lists of klimata found in early geographers vary in their extension, but by convention, they numbered seven, counted from south to north. This number was taken up by Ptolemy who in his Geography divided the northern temperate zone into seven zones (klimata).

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-Biruni, al-Idrisi and al-Razi, the author of the 16th century haft iql&#299;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):


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