Indian Science and Technology in the Eighteenth Century: Some Contemporary European Accounts c9.222

c9.222

82. It should have been remarked before, that M. Bailly has taken notice of the analogy between the Indian method of calculating the places of the planets, and Ptolemy's hypothesis of the equant, though on different principles from those that have been followed here, and such as do not lead to the same conclusion. In treating of the question, whether the sun or earth has been supposed the centre of the planetary motions by the authors of this astronomy, he says, *'Ils semblent avoir reconnu que les deux inegalites (l'equation du centre et la parallaxe de l'orbe annuel) etoient rues de deux centres differens; et dans l'impossibilite ou ils etoient de determiner et le lieu et la distance des deux centres, ils ont imagine de rapporter les deux inegalites aun point qui tint le milieu, c'est-a-dire, a un point egalement eloigne du soliel, et de la terre. Ce nouveau centre resemble assez au centre de l' equant de Ptoleme.'* (Ast. Ind. Disc. Prel. p.69.) The fictitious centre, which M. Bailly compares with the *equant* of Ptolemy, is therefore a point which bisects the distance between the sun and earth, and which, in some respects, is quite different from that *equant*; the fictitious centre, which, in the preceding remarks, is compared with the *equant* of Ptolemy, is a point of which the distance from the earth is bisected by the centre of the orbit, precisely as in the case of that *equant*. M. Bailly draws his conclusion from the use made of half the equation of *schigram*, as well as half the equation *manda*, in order to find the argument of this last equation. The conclusion here is established, by abstracting altogether from the former, and considering the cases of oppositions and conjunctions, when the latter equation only takes place. If, however, the hypothesis of the *equant* shall be found of importance in the explanation of the Indian astronomy, it must be allowed that it was first suggested by M. Bailly, though in a sense very different from what it is understood in here, and from what it was understood in by Ptolemy.