Muhammad B. Muh
MUHAMMAD H. MUH. NASIR AD-DIN AT-TUSI (d. 1273 A.D.)
An Arab astronomer born at Tūs. 1) Az-zīj al-ilkhānī (Astronomical Tables for the Ilkhans) Exc.: MC (1004 r-v) T.: MC A:1
2) At-tadhkira an-naṣiriyya (Memoirs) MS: London, Brit. Mus., MS. Or. 23394 Exc.: MC (1044) T.: MC A: 1
1) Town Long. Lat. Climate Dunqula 5 3° 40• 14° 30• Jarmī (= Aksum) 65° O' 9° 30' (MC 1004 r-v)
2) As for the regions which lie south of the Maghrib (MC: du côté sud-ouest), it is said that travellers who go towards the sources of the Nile of Egypt reach a place beyond Lat. 10° south of the Equator and from there they see, in a southerly direction, the mountains capped with white snow. These are the (mountains called) Jibal al-Qamar (Mountains of the Moon) or Jibal al-Qumr. ... where the sources of the Nile are found. Travellers, however, have never reached the (southern) sea, nor do we possess any correct information about the sea extending north-east (of that country). (MC 1044; MS fol. 39 r.).
Some (scientists) have expressed the opinion that the countries lying in the Fourth Climate possess the most balanced (climatic) conditions. If, by "balanced conditions" we mean such climatic conditions that are (constantly) even (tashābuh al-aḥwāl), this applies to the Equator with greater reason (than to the Fourth Climate). But if (by "balanced conditions") we means a temperate (climate) middle between the two extremes, this is not the case of the Equator. In fact, the black complexion and the kinky hair of the inhabitants of the equatorial regions such as the Zanj and the Ḥabasha prove that the air, in their countries, is extremely hot. Just the opposite is observed among the inhabitants of the Fourth Climate, and this proves that here the air is temperate. The general reason, however, why the Seven Climates are more densely populated and have a higher birth rate than all the other known regions of the Earth, must be another. (MC 1044; MS fol. 41 v - 42 r).