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

26 ASTRONOMY IN ANCIENT NATIONS
surface in one point." The axis of the excentric sphere is incli-
ned to that of the mumaṭṭal sphere, which causes the motion in
latitude. The lunar system comprises an additional sphere outside
the others, the centre of which coincides with the centre of the
world, and which is called al-gauzahar, signifying the constella-
Fig. 2.—Spheres of Mercury

1. Upper Apsis. 2. Lower Apsis. Upper Apsis of deferent sphere.
2. Deferent sphere. 4 Lower Apsis of deferent sphere. 6. Epicycle.
3. Mercury. 8. Surrounding complement. 9. Surrounded part of
   Mumaṭṭal sphere. 10. Mudīr sphere. 11. Centre of the world.
4. Centre of Mudīr. 13. Centre of deferent sphere.
   tion Draco, as this sphere provides for the revolution of the lunar
   nodes ("the head and tail of the dragon") round the zodiac. The
   inner one of the two concentric spherical surfaces, between which
   the excentric sphere lies, surrounds immediately the fire sphere of
   the Earth. The system of Mercury is more complicated, as a
   space had to be provided for the revolution of the centre of the
   (Continued from previous page)
   one is that of the concentric oblique intersphere (called the mail sphere or
   the sphæra deflectens) round the centre of the world, 11°9′ per day, by which
   amount the lunar apogee moves towards the west. The third motion is
   that of the excentric, carrying the centre of the epicycle 24°22′ towards the
   east. The fourth is the motion on the epicycle. Abu 'l Faraj, p. 27.