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    Latitude from length of day
    From: John Huth
    Date: 2009 Nov 17, 15:18 -0500
    I'd posted previously a question as to whether anyone actually used length of day to determine latitude.   I actually stumbled upon the work of a medieval Arab geographer, Yaqut, who used the length of day as a method of marking the zones of the 7 "climes" of the "occupied world".   I think both the idea of climes and occupied world (oecumene) is Greek in origin, but I was unaware of a classification scheme based on the length of day.  

    In this case, he uses the length of day at the summer solstice.   Knowing this information, one can figure out the latitudes of the boundaries of his climes.     He also uses the length of a shadow stick at the equinox at meridian passage, but there are too many inconsistencies in his account.   Length of day seems better.

    Does anyone know who a medieval Arab would measure the length of day?   Sun-dial simply?   Klepsidra? Hour glass?

    Clime listing from Wadie Jwaideh’s translation of Yaqut’s Mu-Jam Al-Buldan

     

    First clime

     

    Longest day = 12 ½ hours at southern end (12 ¾ from al-Biruni, Tafhim)

    13 hours = middle

    13 ¼ = northern end

     

    12 ½ = 9o N, 12 ¾ = 12o N

    13 hours = 17o N

    13 ¼ = 21o N

     

    Locations cited:  

     

    Southern China,  Ceylon/Sarandib/Cerendin, seacoast of “Sind” , Yaman, Sea of Qulzum (Alcuzum in Marseilles tables), Abyssini, Nile, ends in the Sea of Maghrib.   

     

    Island of al-Kark, southern India, Sanaa, Aden, Hadramawt, Najran, Jurash, Jayshan, Sa’dah, Saba, Zufar, Mahrah, Uman.   Lands of the Maghrib:  Tabalah, Jarmi, capital city of Abyssinia, Dumqalah, capital city of Nubia, southern Berbers, Ghanah (country of the Sudan of the Maghrib) and then the Green Sea.   Green Sea = surrounding ocean

     

    Note that Cerendin is listed as 3o N in Marseilles tables.

     

    It is the clime of Saturn, agreed by the Persians and Byzantines.   Capricorn and Aquaris are its signs. 

     

    Second clime

     

     

    13 ¼   hours at southern end 21o N

    13 ½   hours = middle  24o N

    13 ¾    = northern end 28o N

     

    Passes:   China, India (northern parts – Sind, Qamrun, Kanuj), confluence of the Sea of Basrah and the Green Sea, the lands of Najd, Tihamah and Al-Bahrayn, the Sea of Qulzum, the Nile  and the lands of the Maghrib.

     

    Cities:   al-Mansurah, the lands of the Tatars, Daybul.    Yathrib, furthest southern section is a bit beyond Mecca,  Ansina, Aswan.

     

    It is the clime of Jupiter according to the Persians, according to the Byzantines, it is the clime of the Sun.   Sagittarius and Pisces are its signs. 

     

    Third clime

     

    13 ¾    hours at southern end 28o N

    14   hours = middle  31o N

    14 ¼     = northern end 34o N

     

    Kabul, Alexandria, Baghdad, Qandahar, Tyre, Beruit, Kabul, Damascus, Tyre, Jerusalem, Gaza, Qulzum, Damietta, Tangier

     

    Clime of Mercury, Aries and Scorpio

     

    Fourth clime

     

    14 ¼   hours at southern end 34o N

    14 ½    hours = middle  37o N

    14 ¾    = northern end 39o N

     

    Cyprus, Rhodes, Sicily, Straits of Gibraltar, Aleppo, Antioch, Adana, Samarra, Persepolis

     

    Clime of Jupiter, Leo

     

    Fifth clime

     

    14 ¾   hours at southern end 39o N

    15     hours = middle  42o N

    15 ¼    = northern end 44o N

     

    Farghanah, Samarqand, Bukhara, Sea of the Khazars, Armenia, Rumiyah al-Kubra (Rome)

     

    Clime of Venus, Taurus and Libra

     

    Sixth clime

     

    15 ¼   hours at southern end 44o N

    15 ½   hours = middle  46o N

    15 ¾    = northern end 47o N

     

    Constantinople, Heraclea

     

    Clime of Mercury (Persians), Moon (Byzantines), Gemini and Virgo

     

    Seventh clime

     

    15 ¾   hours at southern end 47o N

    16   hours = middle  49o N

    16 ¼     = northern end 51o N

     

    Rus, Varangians, Slavs, Suwar

     

    “The end of this clime marks the end of the oecumene, beyond which no one is to be found save a people of no consequence.   In their impoverished state and lack of refinement, they are more like wild beasts than men. “

     

    Clim of the Moon (Persians), Mars (Byzantines), Cancer.

     

     

     

     

     

     

     


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