A History of the Kerala School of Hindu Astronomy (in Perspective) c9.s5.12

c9.s5.12

An extremely significant class of astronomical treatises from Kerala refers to disquisitions on the rationale of astronomical formulae and procedures. Short expositions of this nature occur in commentarial literature, especially in the commentaries of Parameśvara, Nilakaṇṭha Somayāji and Nārāyaṇa, author of Kriyākramakarī on the Līlāvatī. Single or groups of verses and short tracts pertaining to the exposition of specific points or procedures are often found inscribed on end-leaves of astronomical codices, without indication of source or author. These go mostly unnoticed or ignored by cataloguers of manuscripts. It would, indeed, be highly worthwhile to record, study and analyse these passages with a view to see if some of them contain anything important. In this connection, the discovery of some full-fledged treatises devoted to the exposition of astronomical theories and processes ought to be highly interesting to scholars and historians of mathematics. These texts, which, generally, have the words *yukti* or *nyāya* ‘rationale’ attached to their titles, explain, interpret and discuss the formulae used and procedures followed in the topics which the texts deal with. Among works of this nature may be mentioned the *Grahaṇa-nyāya-dīpikā* on the computation of eclipses and *Vākyakaraṇa* on the formulation of astronomical mnemonics, both by Parameśvara of Vaṭaśreṇi, the *Yukti-bhāṣā* and *Gaṇita-yukti-bhāṣā*, the former and, possibly the latter too, by Jyeṣṭhadeva, the *Nyāya-ratna* by Puṭumana Somayājī, the *Gaṇita-yuktayaḥ* by an anonymous ‘Bhāradvāja brāhman’ and the *Rāśigola-sphuṭānīti* on ‘Reduction to the ecliptic’ by Acyuta Piṣāraṭi. The *Sundararāja-praśnottara* by Nīlakaṇṭha Somayājī, in which he has explained certain astronomical theories and practices in answer to queries raised by a contemporary astronomer Sundararāja of the Tamil country, also belongs to this category of works. It may also be noted that works solely devoted to the demonstration of procedures call themselves *-kriyā* or *-kriyākrama*, e. g., *Saṅgrahasādhana-‘kriyā’* and *Uparāga-‘kriyākrama’*.