# Magnus Sinus

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Ancient cartographical feature known today as the Gulf of Thailand and surrounding areas

The 11th Asian regional map from [Ptolemy](/source/Claudius_Ptolemy)'s *[Geography](/source/Ptolemy's_Geography)* ([Harleian MS 7182](https://en.wikipedia.org/w/index.php?title=Harleian_MS_7182&action=edit&redlink=1))

The **Magnus Sinus** or **Sinus Magnus** ([Latin](/source/Latin); [Ancient Greek](/source/Ancient_Greek_language): ὀ Μέγας Κόλπος, *o Mégas Kólpos*),[1][2] also [anglicized](/source/Anglicization_of_names) as the **Great Gulf**, was the form of the [Gulf of Thailand](/source/Gulf_of_Thailand) and [South China Sea](/source/South_China_Sea) known to [Greek](/source/Greek_geographers), [Roman](/source/Roman_geographers), [Arab](/source/Medieval_Arab_geographers), [Persian](/source/Medieval_Persian_geographers), and [Renaissance cartographers](/source/Renaissance_cartographers) before the [Age of Discovery](/source/Age_of_Discovery). It was then briefly conflated with the [Pacific Ocean](/source/Pacific_Ocean) before disappearing from maps.

## History

Further information: [Sino-Roman relations](/source/Sino-Roman_relations), [Daqin](/source/Daqin), [Chinese cartography](/source/Chinese_cartography), and [Chinese geography](/source/Chinese_geography)

The gulf and its major port of [Cattigara](/source/Cattigara) had supposedly been reached by a 1st-century [Greek](/source/Ancient_Greeks) trader named Alexander, who returned safely and left a [periplus](/source/Periplus) of his voyage.[3] His account that Cattigara was "some days" sail from [Zaba](https://en.wikipedia.org/w/index.php?title=Zaba_(Ptolemy)&action=edit&redlink=1) was taken by [Marinus](/source/Marinus_of_Tyre) of [Tyre](/source/Tyre_(city)) to mean "numberless" days and by [Ptolemy](/source/Ptolemy) to mean "a few".[4][note 1] Both Alexander and Marinus's works have been lost, but were claimed as authorities by Ptolemy in [his *Geography*](/source/Ptolemy's_Geography).[8] Ptolemy (and presumably Marinus before him) followed [Hipparchus](/source/Hipparchus) in making the [Indian Ocean](/source/Indian_Ocean) a landlocked sea, placing Cattigara on its [unknown eastern shoreline](/source/Terra_incognita). The expanse formed between it and the [Malay Peninsula](/source/Malay_Peninsula) (the "[Golden Chersonese](/source/Golden_Chersonese)"), he called the Great Gulf.[9]

[Ptolemy's *Geography*](/source/Ptolemy's_Geography) was translated into [Arabic](/source/Arabic_language) by a team of scholars including [al-Khwārizmī](/source/Al-Khw%C4%81rizm%C4%AB) in the 9th century during the reign of [al-Maʿmūn](/source/Al-Ma%CA%BFm%C5%ABn). By that time, Arab merchants such as [Soleiman](/source/Soleiman_the_Merchant) had begun regular commerce with [Tang China](/source/Tang_China) and, having passed through the [Strait of Malacca](/source/Strait_of_Malacca) *en route*, shown that the Indian Sea communicated with the [open ocean](/source/World_Ocean). African traders similarly showed[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] that the coastline did not turn sharply east south of [Cape Prasum](/source/Cape_Prasum) below [Zanzibar](/source/Zanzibar) as Ptolemy held.[10] [Al-Khwārizmī](/source/Al-Khw%C4%81rizm%C4%AB)'s influential *[Book of the Description of the Earth](/source/Book_of_the_Description_of_the_Earth)*, therefore, removed Ptolemy's unknown shores from the Indian Ocean. The robustly-described lands east of the Great Gulf, however, were retained as a phantom peninsula (now generally known as the [Dragon's Tail](/source/Dragon's_Tail_(peninsula))).

Just after 1295, [Maximus Planudes](/source/Maximus_Planudes) restored Ptolemy's Greek text and maps at [Chora Monastery](/source/Chora_Monastery) in [Constantinople](/source/Constantinople) ([Istanbul](/source/Istanbul)). This was translated into Latin at [Florence](/source/Republic_of_Florence) by [Jacobus Angelus](/source/Jacobus_Angelus) around 1406 and quickly spread the work's information and misinformation throughout Western Europe. The maps initially repeated Ptolemy's enclosed Indian Sea. Following word of [Bartholomew Dias](/source/Bartholomew_Dias)'s circumnavigation of Africa, maps by [Martellus](/source/Henricus_Martellus) and by [Martin of Bohemia](/source/Martin_of_Bohemia) replaced this with a new form of the [Dragon's Tail peninsula](/source/Dragon's_Tail_peninsula), including details from [Marco Polo](/source/Il_Milione). As early as 1540, [continuing exploration](/source/Age_of_Discovery) led [Sebastian Münster](/source/Sebastian_M%C3%BCnster) to conflate the Great Gulf with the [Pacific Ocean](/source/Pacific_Ocean) west of the [Americas](/source/Americas), supposing that the 1st-century Alexander had crossed to a port in [Peru](/source/Viceroyalty_of_Peru) and safely returned.[4] The idea was repeated by [Ortelius](/source/Ortelius) and others.[11] (Some modern [South American](/source/South_America) scholars have returned to the idea as recently as the 1990s, but there remains no substantial evidence to support the idea.[12]) The Great Gulf was finally dispensed with in all its forms as more accurate accounts returned from both the [East](/source/East_Indies) and [West Indies](/source/West_Indies).

A detail from a 1794 map showing the common identification of the Great Gulf with the Gulf of Thailand[13]

## Details

The details of the Great Gulf changed somewhat among its various forms, but the ancient and Renaissance [Ptolemaic accounts](/source/Ptolemy's_Geography) had it bound on the west by the [Golden Chersonese](/source/Golden_Chersonese) and on the north and east by the ports of the [Sinae](/source/Sinae), chief among which was [Cattigara](/source/Cattigara).[14] [Medieval Islamic cartographers](/source/Medieval_Islamic_cartographers) followed [al-Khwārizmī](/source/Al-Khw%C4%81rizm%C4%AB) in having a strait southeast of the gulf communicating with the [Sea of Darkness](/source/Sea_of_Darkness). Believing the [circumference of the Earth](/source/Circumference_of_the_Earth) to follow Ptolemy's reduced figures or even smaller ones, cartographers during the early phases of the [Age of Discovery](/source/Age_of_Discovery) expanded the Gulf to form the [Pacific Ocean](/source/Pacific_Ocean) west of [South America](/source/South_America), considered to represent a [southeastern peninsula](/source/Dragon's_Tail_(peninsula)) of Asia.

Modern reconstructions agree in naming the [Golden Chersonese](/source/Golden_Chersonese) a form of the [Malay Peninsula](/source/Malay_Peninsula) but differ in their considerations of how much of the [South China Sea](/source/South_China_Sea) to include within Ptolemy's reckoning of the Great Gulf. Those following Alexander's route from Zaba on its northern shore to Cattigara to its southeast consider it to be no more than the [Gulf of Thailand](/source/Gulf_of_Thailand), with Cattigara located in the [Funanese](/source/Kingdom_of_Funan) [Óc Eo](/source/%C3%93c_Eo) ruins at [Thoại Sơn](/source/Tho%E1%BA%A1i_S%C6%A1n). Its [Cottiaris River](https://en.wikipedia.org/w/index.php?title=Cottiaris_River&action=edit&redlink=1) would then be a former course of the [Mekong](/source/Mekong_River) which once passed the site to enter the [Gulf of Thailand](/source/Gulf_of_Thailand).[15][16][3] Others ignoring the route as garbled but taking Cattigara to be the major [Han](/source/Han_Empire) entrepôt of [Longbian](/source/Longbian_Commandery) consider the Great Gulf to have been the [Gulf of Tonkin](/source/Gulf_of_Tonkin), hypothesizing that the Gulf of Thailand (if present) was represented by the smaller inlet on the eastern shore of the Golden Chersonese. Its Cottiaris River would have been [Vietnam](/source/Vietnam)'s [Red River](/source/Red_River_(Vietnam)). [Panyu](/source/Panyu) ([Guangzhou](/source/Guangzhou)) had been the major port of the [Kingdom of Nanyue](/source/Kingdom_of_Nanyue) but identifications of Ptolemy's Cattigara with Han-era [Nanhai](/source/Nanhai_Commandery), though common in the past,[17][18] are credited little more than those placing it in Peru.

## Notes

1. **[^](#cite_ref-8)** "Marinus does not exhibit the mileage from the [Golden Chersonese](/source/Golden_Chersonese) to [Cattigara](/source/Cattigara). But he says that Alexander has described the land beyond to lie facing the south, and that after sailing by this for 20 days you reach the city of Zaba, and still saying on for some days southward but rather to the left [i.e., east] you reach Cattigara. He exaggerates the distance, for the expression is *some days* not *many days*. He says indeed that no numerical statement of the days was made because they were so many: but this I take to be ridiculous."[7]

## Citations

1. **[^](#cite_ref-FOOTNOTEPtolemyc._150Vol. VII,_§3_&_5_1-0)** [Ptolemy (c. 150)](#CITEREFPtolemyc._150), Vol. VII, §3 & 5.

1. **[^](#cite_ref-FOOTNOTEAgathemerusVol. I,_p. 53_2-0)** [Agathemerus](#CITEREFAgathemerus), Vol. I, p. 53.

1. ^ [***a***](#cite_ref-FOOTNOTEGlover2005_3-0) [***b***](#cite_ref-FOOTNOTEGlover2005_3-1) [Glover (2005)](#CITEREFGlover2005).

1. ^ [***a***](#cite_ref-FOOTNOTESuárez199999_4-0) [***b***](#cite_ref-FOOTNOTESuárez199999_4-1) [Suárez (1999)](#CITEREFSuárez1999), p. 99.

1. **[^](#cite_ref-FOOTNOTEPtolemyc._150_5-0)** [Ptolemy (c. 150)](#CITEREFPtolemyc._150).

1. **[^](#cite_ref-FOOTNOTEYule1866cl_6-0)** [Yule (1866)](#CITEREFYule1866), p. cl.

1. **[^](#cite_ref-7)** Ptolemy,[5] translated by Yule.[6]

1. **[^](#cite_ref-FOOTNOTEPtolemyc._150Vol. I,_§14_9-0)** [Ptolemy (c. 150)](#CITEREFPtolemyc._150), Vol. I, §14.

1. **[^](#cite_ref-FOOTNOTEBunbury1911625_10-0)** [Bunbury (1911)](#CITEREFBunbury1911), p. 625.

1. **[^](#cite_ref-FOOTNOTEBunbury1911624_11-0)** [Bunbury (1911)](#CITEREFBunbury1911), p. 624.

1. **[^](#cite_ref-FOOTNOTESuárez199971_12-0)** [Suárez (1999)](#CITEREFSuárez1999), p. 71.

1. **[^](#cite_ref-FOOTNOTERichardson2003_13-0)** [Richardson (2003)](#CITEREFRichardson2003).

1. **[^](#cite_ref-FOOTNOTEd'Anville1763_14-0)** [d'Anville (1763)](#CITEREFd'Anville1763).

1. **[^](#cite_ref-FOOTNOTEVaux1854b_15-0)** [Vaux (1854b)](#CITEREFVaux1854b).

1. **[^](#cite_ref-FOOTNOTEHerrmann1938_16-0)** [Herrmann (1938)](#CITEREFHerrmann1938).

1. **[^](#cite_ref-FOOTNOTEMalleret1962_17-0)** [Malleret (1962)](#CITEREFMalleret1962).

1. **[^](#cite_ref-FOOTNOTESmith1854_18-0)** [Smith (1854)](#CITEREFSmith1854).

1. **[^](#cite_ref-FOOTNOTEVaux1854a_19-0)** [Vaux (1854a)](#CITEREFVaux1854a).

## References

- [Agathemerus](/source/Agathemerus), *Tē̂s Geōgraphías Hypotypṓseis en Epitomē̂i* τῆς γεωγραφίας ὑποτυπώσεις ἐν ἐπιτομῇ [*A Sketch of Geography in Epitome*] (in Greek)

- d'Anville, Jean Baptiste Bourguignon (1763), [*Orbis Veteribus Notus*](http://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~3039~410038:Orbis-Veteribus-Notus-) [*The World Known to the Ancients*] (in Latin), Paris

- Bunbury, Edward Herbert; Beazley, C. Raymond (1911), ["Ptolemy: Geography"](https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Ptolemy#Geography), in [Chisholm, Hugh](/source/Hugh_Chisholm) (ed.), *[Encyclopædia Britannica](/source/Encyclop%C3%A6dia_Britannica_Eleventh_Edition)*, vol. 22 (11th ed.), Cambridge University Press, pp. 623–626.

- Glover, Ian C. (2005), ["Cattigara"](https://books.google.com/books?id=bVWcAQAAQBAJ&pg=PA292), in Hornblower, Simon; Spawforth, Antony (eds.), *The Oxford Classical Dictionary* (3rd ed.), Oxford University Press, p. 292, [ISBN](/source/ISBN_(identifier)) [9780198606413](https://en.wikipedia.org/wiki/Special:BookSources/9780198606413)

- Herrmann, Albert (1938), "Der Magnus Sinus und Cattigara nach Ptolemaeus" [The Magnus Sinus and Cattigara in Ptolemy], *Géographie Historique et Histoire de la Géographie*, Comptes Rendus du 15me Congrès International de Géographie, Amsterdam, 1938 (in German), vol. II, Leiden: Brill, §IV, pp. 123–128

- Malleret, Louis (1962), "XXV: Oc-Èo et Kattigara" [Oc-Èo and Cattigara], *L'Archéologie du delta du Mékong* [*Archaeology of the Mekong Delta*] (in French), vol. III, pp. 421–454

- [Ptolemy](/source/Claudius_Ptolemy) (c. 150), [*Geōgraphikḕ Hyphḗgēsis* Γεωγραφικὴ Ὑφήγησις](/source/Ptolemy's_Geography) [*The Geography*] (in Greek), Alexandria

- Richardson, William A.R. (2003), "South America on Maps before Columbus? Martellus's 'Dragon's Tail' Peninsula", *Imago Mundi*, vol. 55, pp. 25–37, [doi](/source/Doi_(identifier)):[10.1080/0308569032000097477](https://doi.org/10.1080%2F0308569032000097477), [S2CID](/source/S2CID_(identifier)) [129171245](https://api.semanticscholar.org/CorpusID:129171245)

- Smith, Philip (1854), ["Cattigara"](https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0064%3Aalphabetic+letter%3DC%3Aentry+group%3D9%3Aentry%3Dcattigara-geo), in Smith, William (ed.), *Dictionary of Greek and Roman Geography, Illustrated by Numerous Engravings on Wood*, vol. I, London: Walton & Maberly, p. 570

- Suárez, Thomas (1999), [*Early Mapping of Southeast Asia*](https://books.google.com/books?id=wQTQAgAAQBAJ), Singapore: Periplus Editions, [ISBN](/source/ISBN_(identifier)) [9781462906963](https://en.wikipedia.org/wiki/Special:BookSources/9781462906963)

- Vaux, William Sandys Wright (1854a), ["Cottiaris"](https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0064%3Aalphabetic+letter%3DC%3Aentry+group%3D23%3Aentry%3Dcottiaris-geo), in Smith, William (ed.), *Dictionary of Greek and Roman Geography, Illustrated by Numerous Engravings on Wood*, vol. I, London: Walton & Maberly, p. 698

- Vaux, William Sandys Wright (1854b), ["Magnus Sinus"](https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0064%3Aalphabetic+letter%3DM%3Aentry+group%3D2%3Aentry%3Dmagnus-sinus-geo), in Smith, William (ed.), *Dictionary of Greek and Roman Geography, Illustrated by Numerous Engravings on Wood*, vol. II, London: Walton & Maberly, p. 253

- [Yule, Henry](/source/Henry_Yule) (1866), ["Extracts from the Geography of Ptolemy. (Circa A.D. 150)"](https://archive.org/stream/CathayAndTheWayThitherVol1/Cathay_and_the_way_thither_a_collection#page/n159/mode/2up/search/Marinus), *Cathay and the Way Thither; Being a Collection of Medieval Notices of China with a Preliminary Essay on the Intercourse between China and the Western Nations Previous to the Discovery of the Cape Route*, vol. I, London: Hakluyt Society, pp. cxlvi–cliii

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Adapted from the Wikipedia article [Magnus Sinus](https://en.wikipedia.org/wiki/Magnus_Sinus) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Magnus_Sinus?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.