1839.] Description of an Astronomical Instrument. 837 



Cos. decl. : 1 : : Chitija ; Sin chara 



00091609 

 8-9693648 



8-9785257= 5° 28' nearly,— ascensional diff. 

 Again, the Lugna of Lanca, or right ascension, is, 

 + 17° 50' 

 Chara — 5° 2 8' 



Gives 22°. 22' the ascension of the sign Aries at Khota, 



22 366 

 which being reduced to Dundas gives us — ^ — = 3.726=3 dundas 43 



pulas nearly, as given on the plate, notwithstanding that my calcula- 

 tions have been performed with logarithms ; a sufficient proof, if proof 

 were needed, that where care can save him from error the Indian astro- 

 nomer is not wanting. It will be seen that I have assumed the obliquity 

 of the ecliptic to have been estimated at 24°, which assumption gives 

 me the true result; this supports the statement made in the beginning 

 of this article, that the instrument is not beholden to modern science 

 for the principles of its construction. Calculating by spherical trigono- 

 metry, and assuming the same obliquity, I obtain 3 dundas and 40 

 pulas for the ascensional arc, giving a difference in time of 3 pulas, 

 or about one of our minutes; an error so small, that even were the 

 Indian astronomer aware of its existence he would disregard it, satisfied 

 that the practical purposes which his labours subserve, are, notwith- 

 standing, carried out with sufficient accuracy. 



The zones which bound this side of the instrument alone remain to 

 be explained. There are two of them, with their subordinate circles, 

 the inner serving for an hour circle, the outer for the Bhagana or zodiac. 

 It will be observed that in the latter the signs are arranged in pairs, and 

 are referred to the hour circle, of which they occupy segments propor- 

 tioned to their times of ascension, as given above, while the pairs whose 

 ascensional arcs are equal, are classed together: viz. Mesha and Minah, 

 (Aries and Pisces) Brisha and Khumbo (Taurus and Aquarius) and 

 so on. The whole zodiac thus occupies an equatorial arc of 12 hours, 

 or 30 dundas. 



Indian astronomers divide their zodiac in the same manner as those 

 of Europe, and have equivalent names for their signs, as appears in the 

 following table. 



