ब्राह्मस्फुटसिद्धान्त (ब्रह्मगुप्त - शून्य, कुट्टक, बीजगणित एवं सम्पूर्ण २१ अध्याय सान्वय सटीक)

24 ASTRONOMY IN ANCIENT NATIONS smallest distances being in substantial agreement with the theory of Ptolemy. Al Battani also gives a similar set of figures, though with some slight differences. He does not mention peculiar treat- ment given by Ptolemy to the theory of Mercury. The above table gives the distance expressed in semidiameters of the Earth. Al Kusgi and diameters of planets Al Kūsgī, one of the astronomers of Ulug Begh, gives a list of the semidiameters of the "concavities" of the planetary sphe- res (i.e. the smallest distances of the spheres) expressed in para- sangs, the diameter of the Earth being 2,545 parasangs.¹ Expres- sed in semidiameters of the Earth, the figures turn out somewhat differrent from those given above, e.g. the smallest distance of the Sun being 1,452 and the greatest of Saturn 26.332, but he does not supply any means of making out how these figures were found. Before leaving this subject, we shall also give the diameters of the planets according to Al Fargani, as they became known in Europe at an early date and were quoted by Roger Bacon and others.² With trifling variations the same values are given by Al Battani, Abu 'l Faraj, and Abraham ben Chija. Apparent True Diameter Diameter (Earth's=1) Moon in apogee ... ... ... 31½' ... 1 : 3½ Mercury, mean dist. ... ... ¹⁄₁₅ of Sun's ... ¹⁄₂₈ Venus " " ... ... ¹⁄₁₀ " ... 1 : 3⅓ Sun " " ... ... 31½' ... 5½ Mars " " ... ... ¹⁄₂₀ of Sun's ... 1⅙ Jupiter " " ... ... ¹⁄₁₂ of Sun's ... 4½ + ¹⁄₁₆ Saturn " " ... ... ¹⁄₁₈ " ... 4¼ Al Kazwini, Abu'l Faraj and Al-Jagmini on Excentric Spheres of the Sun The system of the spheres is set forth in greatest detail in three treatises of later date, the cosmograpy of Zakarija ben Muhammed ben Mahmud al Kazwini (about 1275), the astronomy

1. Astronomica Shah Chelgii, pp. 95-97.
2. There are some slight differences between the figures given in the various editions (J.L.E. Dreyer has compared those of 1493, 1546, and 1669), but those given above agree with the cubic contents according to Al Fargani. The figures of .Kazwini seem to have been greatly corrupted.