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

GOLAYANTRA OR ARMILLARY SPHERE 339
In the Arabic epitome of the Almagest entitled Tahriru'l
mejesti. the armillary sphere, Za ul halk, is thus described :
Two equal circles are placed at right angles, the one
representing the ecliptic, the other the solstitial colure.
Two pins pass throught the poles of the ecliptic and
two other pins are placed on the poles of the equator.
On the first two pins are suspended a couple of circles
moving, the one within, the other without, the
first mentioned circles, and representing two seconda-
ries of the ecliptic. On the two other pins a circle
is placed, which encompasses the whole instrument,
and within which the different circles turn; it repre-
sents the meridian. Within the inner secondary of
the ecliptic, a circle is fitted to it, in the same plane
and turning in it. This is adapted to measure latitudes.
To this internal circle, two apertures or sights, opposite
to each other, and without its plane are adapted like
the sights of an instrument for altitudes. The armil-
lary sphere is complete when consisting of these six
circles. The ecliptic and secondaries are to be gra-
duated as minutely as may be practicable. It is best
to place both secondaries, as by some directed, within
the ecliptic (instead of placing one of them without it),
that the complete revolution of the outer secondary
may not be obstructed by the pins at the poles of the
equator. The meridian likewise should be doubled,
or made to consist of two circles; the external one gra-
duated and the internal one moving within it. Thus the
pole may be adjusted at its proper elevation above the
horizon of any place. The instrument so constructed
consists of seven circles.
It is remarked that when the circle representing the
meridian, is placed in the plane of the true meridian, so
छिद्रं विकृतं कुर्यात् तेन जलं निस्स्रवति । नलकाच्च जलमधो गच्छति । तद्वशाच्च तदस्थमलावु
पारतपूर्त्या गुरुत्वाज्जलेन सहाधो गच्छद् गोलं प्रत्यङ्मुखमाकर्षति । एवं त्रिंशद् घटिकाभिर्व्वसंमितं यथा
जलं भवति गोलस्य चार्धं भ्रमति तथा स्वबुद्ध्या जलनिस्स्रावो योज्यः । इति ।
अमृतस्रावयोगेन कालभ्रमण साधनम् ।
गुणबीजसमाकृष्टं गोलयंत्रं प्रकल्पयेत् ॥ SuSi. XIII, 16-17