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.