EDWARD S. KENNEDY
The historian of the Islamic exact sciences is frequently confronted with an embarras de richesse—hundreds of manuscript sources which have never been studied in modern times. For descriptive geography the situation may well be the same. The reader will find indications to this effect in the surveys of S. Maqbul Ahmad (1965a, b). But for those parts of the subject which employ mathematics, frustration arises from a paucity rather than a plethora of sources. For instance, it is reliably reported (Shawkat 1962:12) that the astronomer Ibn Yūnus (fl. 1000) made a world map for the Fatimid caliph al-‛Azīz. But precise information as to the projection method is not available, much less the map itself.
What information is available can be regarded as involving either geodesy or cartography, and the presentation below is organized under these two main topics. Under the first, the subject of latitude determinations leads to that of geodesy proper, thence to the fixing of longitudes and the zero meridians upon which they were based. The section concludes with an indication of the end-products of these operations—lists of place names with co-ordinates.
In the cartographical section which follows, the lack of precise information alluded to above severely hampers an assessment of the degree to which Hellenistic geography penetrated the Muslim world. The situation of al-Bīrūnī will be seen to be the reverse of al-ldrīsī’s. For the former, projections are adequately described, but no applications to actual maps can be exhibited until the Renaissance or later. For the latter, many copies of the map survive, but the projection methods are largely a matter of conjecture. The maps of other scientists are described, but no attempt is made to cover Muslim navigation or sea charts.