Bīrūnī, Muḥammad ibn Aḥmad, Alberuni's India (v. 2)

(London :  Kegan Paul, Trench, Trübner & Co.,  1910.)

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CHAPTER LVII.                             91

northern latitude, and because also the country (of
the observer) has so much latitude. For in the more
northern regions they are seen both at the beginning
and end of one and the same night, and never dis¬
appear."

They have particular methods for the computation Onthe
of the heliacal rising of Agastya, i.e. Suhail or Canopus. rising of
They observe it first when the sun enters the station
Hasta, and they lose it out of sight when he enters the
station Rohini. Pulisa says : " Take double the apsis of
the sun. If it is equalled by the corrected place of the
sun, this is the time of the heliacal setting of Agastya."

The apsis of the sun is, according to Pulisa, 2| zodiacal
signs. The double of it falls in 10° of Spica, which is
the beginning of the station Hasta. Half the apsis
falls on 10° of Taurus, which is the beginning of the
station Rohini.

Brahmasfupta maintains the following in the emen- Quotation

-,     .          „                                                                                                       from Brah-

dation of the Khandctkhddyaka :—                                     magupta.

" The position of Suhail is 27° Orion, its southern
latitude 71 parts. The degrees of its distance from the
sun necessary for its heliacal rising are 12.

" The position of Mrigavyadha, i.e. Sirius Yemenicus,
is 26° Orion, its southern latitude 40 parts. The de¬
grees of its distance from the sun necessary for its
heliacal rising are 13. If you want to find the time
of their risings, imagine the sun to be in the place of
the star. That amount of the day which has already
elapsed is the number of degrees of its distance from
the sun necessary for its heliacal rising. Fix the
ascendens on this particular place. When, then, the
sun reaches the degree of this ctscendens, the star first
becomes visible.

" In order to find the time of the heliacal setting of
a star, add to the degree of the star six complete zodiacal
signs. Subtract from the sum the degrees of its dis¬
tance from the sun necessary for its heliacal rising, and
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