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

338 BRAHMAGUPTA AND ASTRONOMICAL INSTRUMENTS III. 17) ; also rule for finding the Sun's altitude (BrSpSi. III. 27 ; MBh. III. 24) (The Sun's altitude for the night has been called by Brahmagupta as pātāla-śaṅku, BrSpSi. XV. 9). Golayantra or Armillary Sphere The first mention of the Golayantra or the armillary sphere is in the Āryabhaṭīya (Golapāda. 22)¹ which was a uniformly round circle made of wood or of bamboo and which was of uniform weight or density alround. It was levelled with mercury, oil or water. A śalākā or pin (or rod) was fixed in it in the south-north direction. Its description from the com- mentary Bhaṭadīpikā of Paramādiśvara is given here : A sphere of wood. uniformly round on all sides and with uniform density, and also light is made to revolve round an iron axis fixed north-south without friction (oil may be introduced to avoid friction). To the backside of the sphere, is fixed a nālaka full of water which has the length equal to the circumference of the sphere: and which has a hole at the bottom. Now a thread, connected to the hook of the wooden ball (on the top side) passing over another small ball (in the same axis of the wooden ball) is attached to the mercury lobe by its other end. The mercury lobe is placed on the level of water and water is allo- wed to flow through the bottom hole and with water mercury lobe also goes down. The time in which the above hook of ball comes to bottom (180°) is noted. The experiment is repeated with oil. The use of this mechanism is to revolve the ball by water or oil¹

1. काष्ठमयं समवृत्तं समन्ततस्सम गुरु लघु गोलम् । पारतं तैलजलैस्तं भ्रमयेत्स्वधिया च कालसमम् ॥ Arya. IV. 22 काष्ठमयं वंशादि काष्ठेन निर्मितं समवृत्तं सर्वतोवृत्तं समन्ततस्सम गुरुं सर्वावयवेषु समं गुरुत्वं यथा भवति तथा कृतं । लघुमगुरुं एवं भूतं गोलं कृत्वा पारतादिभिस्तं स्वधिया च कालसमं भ्रमयेत् । अयमर्थः । भूमिष्ठ दक्षिणोत्तरस्तम्भयोरुपरि गोलप्रोतायश्शलाकाया अग्रे स्थापयेत् । गोलदक्षिणोत्तरा- च्छिद्रे च तैलेन सिञ्चेत् यथा निस्सङ्गो गोलो भ्रमति । गोलस्यापरतो गोलपरिधिसंमित दैर्ध्यं साधश्छिद्रं जलपूर्णं नलकं निदध्यात् ततो गोलस्यापरस्वस्तिक कीलकं विधाय तस्मिन्सूत्रस्यैक मग्रं बद्ध्वादौ विषुवन्मण्डलपृष्ठेन प्राङ्मुखं नीत्वा तदग्रबद्धं पारतपूर्णमलावु जलपूर्णे नलके निदध्यात् ततो नलकस्याध [Cont. on Page 337]