The first is the Earth, over which is Water, but not encompassing it entirely. Above this is Fire, towards its northern extremity shaped like a myrobalan. Above this again is the Air, but its concave surface is not spherical. The Air is of nine kinds. Bhúváyu, is the atmosphere extending up to the height of forty-seven kos from the globe of the earth. It is volatile in every direction and is the region wherein rain, thunder and lightning take their origin. Avaha is the air from the last-mentioned body to the moon. Pravaha, from the second to Mercury. Udvaha from the third to Venus. Saṃvaha, from the fourth to the Sun. Suvaha, from the fifth to Mars. Parivaha, from the sixth to Jupiter. Parávaha, from the seventh to Saturn. Pravahánila, from the eight to the fixed stars. Day and night are formed by the revolution of this wind, with a movement from east to west, the other seven winds reversing this order of motion.* But their more authoritative opinion is that those seven form the Pravahánila, and are named after the seven planets and all revolve from east to west.* Their knowledge does not extend beyond the fixed stars. Ether transcends all other spheres and is unfathomable.

The mean motions of the planets which they call Madhyama differ from the Greek reckoning in the seconds and thirds. Thus, in a nychthemeron extending from midnight to midnight, the Súrya-Siddhánta gives the following calculations.

According to the Greeks.

The motion of the Planets is considered of their essence and is of equal velocity in all. When calculated in kos their rate of motion is said to be 11,858 yojana* and 3 kos in the space of a nychthemeron, and their direc­tion is from west to east. The difference in their periods arises from the greater or less extent of their orbits, the superior being greater than those lower in position.

The progression of the fixed stars they consider to be somewhat simi­lar to that of the planets, but differing from the Greeks, they assert that with regard to the Lunar stations, there is a motion of 54 seconds* in one year, or one degree in 66 years and 8 months. They* compute that the asterisms advance 27* degrees from the beginning of Aries, or according to another calculation, having advanced 24 degrees, they have a retrograde motion till they reach the 28th degree of Pisces whence they return to Aries, and the same movement re-commences. The Ursa Major which is called in Sanskrit Sapta-ṛishi* (the seven Sages) has a precession in one year of 17 seconds, 47 thirds from west to east, or one degree in 200 years and 6 months, and accomplishes its revolution. One sect considers the operation of these forces to depend solely on the power of the Almighty.

The ancient Greeks, including Aristotle, were ignorant of the motion of the fixed stars and Hipparchus observed a few* with a motion from east to west in the Zodiac, but he was unable to calculate their dimen­sions. Ptolemy determined the motion of the stars in longitude to be one degree in a hundred solar years. Ibn A´ạlam and others reckoned sixty. The observations of Naṣír'uddín Ṭúsi agree with this last, but Muhyi'ddín Maghrabi* and a number of experts at the same observatory discovered that Aldebaran, the Heart of Scorpio (<Greek> Scorpii), and others, advanced a degree in 66* years. In the Gurgáni Tables (of Ulugh Beg) this is made to occur in 70 Yazdajirdi* years, each of which is 365 years without a fraction.