INTRODUCTION.

treatise; or if we notice the values assigned in XVII 1. 2 to the epicycles In ancient astronomy, an epicycle is a small circle whose center moves around the circumference of a larger one; used here to calculate planetary positions. of the apogee which altogether differ from those stated in the modern Sûrya Siddhânta The "Sun Doctrine," one of the most important historical Sanskrit treatises on Indian astronomy.; we are driven to the conclusion that in these and similar points the treatise used by Varâha Mihira A 6th-century Indian astronomer and polymath. really differed from the modern one known to us. For we are altogether unable to imagine any reason why Varâha Mihira should have changed, in the details referred to, the doctrines of the book which he aims at epitomizing.

There is however a series of other cases in which the decision is not quite so simple. While, as remarked above, the mathematical processes prescribed in the old Sûrya Siddhânta agree on the whole with those of the modern treatise, it at once appears that Varâha Mihira whose intention it is to write a karaṇa A concise astronomical handbook or manual used for practical calculations rather than theoretical study. considers himself entitled to represent the teaching of his original in a somewhat condensed form, facilitating the quick despatch of the required astronomical calculations. What he for instance says, in the first chapter, about the yuga An era or cycle of time. of the Sûrya Siddhânta, clearly is an abbreviated statement of the corresponding doctrines of the old Sûrya Siddhânta, and we therefore have no reason to doubt of the old Siddhânta, as well as the modern one, having taught that 4,320,000 years constitute a great age, and that one thousand such great ages go to a kalpa An eon, or a "day of Brahma," equaling 4.32 billion years.. The fact is that for all the merely theoretical part of a Siddhânta there is no room in the karaṇa, and that hence the latter does all that is required if, instead of describing the great periods of the world, it states the smallest possible aggregate of years comprising an integral number of lunar months and natural days. So far we have no reason to hesitate in accepting Varâha Mihira's statements as a faithful, though somewhat modified, rendering of the meaning of the old Sûrya Siddhânta; the question however assumes a somewhat different aspect when we compare the number of natural days contained, on the one hand, within the mahâyuga A "great age" consisting of 4,320,000 solar years. of the modern Sûrya Siddhânta, and, on the other hand, within the corresponding period according to Varâha Mihira. The modern Sûrya Siddhânta teaches that a mahâyuga of 4,320,000 years comprises 1,593,336 intercalary months Extra months added to the lunar calendar to keep it in sync with the solar year. and 25,082,252 omitted lunar days, whence it follows that the number of sâvana days A natural or civil day, measured from sunrise to sunrise. contained within the same period amounts to 1,577,917,828. Varâha Mihira on the other hand, following his Sûrya Siddhânta, states that a period of 180,000 years comprises 66,389 intercalary months and 1,045,095 omitted lunar days, so that a mahâyuga (= 24 x 180,000 years) consists of 1,577,917,800 sâvana days, i. e. 28 days less than according to the modern Sûrya Siddhânta. Here it certainly appears possible that Varâha Mihira should have slightly diminished the number of the sâvana days of the mahâyuga, and implicitly the length of the solar year, in order to be able to reduce