In the opinion of the most competent critics, these works, which are chiefly empirical methods of determining the positions of the stars, are inferior to those which the Alexandrians have left us. Yet, in matters relating to the measurement of arcs and to spherical trigonometry, they reveal a more advanced state of the science. It is impossible to determine at what period this new astronomical science was constituted in India. Some of its theories squarely betray their indebtedness to Greek science, as, for instance, that of the displacement of the equinoctial and solstitial points by a periodical vibration or tremor. We can also say as much of the solar zodiac, the names of the constellations of which strikingly resemble the Greek names in form as well as in significance, and the same of the names of the chief planets. Other expressions are found, notably in the works of Varâha-Mihira, which indicate, if not a borrowing, a contact, at least, with the works of the Greek astronomy, of which Mr. Burgess gives a fairly complete list in his Notes on Hindu Astronomy and the History of our Knowledge of it, in the Journal of the Royal Asiatic Society. Among these terms, some are Greek words which have been utilized in naming constellations or astronomical measures; others have retained the special significations which they had in the works of the Alexandrian astronomers. It would certainly be an exaggeration to insist that the adoption of a foreign term of necessity implies the borrowing of the idea which it expresses. It is, nevertheless, probable that the Sanskrit writers would not have made use of so many of these exotic denominations if the ideas they represent had already found their expression in the languages of India. Further, among the fine Siddântas which Varâha-Mihira collected and condensed as including all the astronomical science of his time, there are two, the _Romaka_ and the _Pauliça_, the names of which suggest directly--the first the scientific culture of the Roman world, and the other Paulus, a celebrated Alexandrian astronomer of the third century A. D.[8] [Footnote 8: The Romaka Siddânta employs, as a measure of time, the _Guga_ of 2,850 years or 1,040,953 days, giving a tropical year of 365 days, 5 hours, 55 minutes, and 12 seconds, which is exactly the figure proposed by Ptolemy and Hipparchus.--_Burgess, Journal of the Royal Asiatic Society._] We apparently find, likewise, the names of Manetho (fourth century A. D.) in _Manittha_ or _Manimda_; of Spensippus in _Sporedjivadja_; and of Ptolemy in _Asoura Maya_, whom the _Sounya Siddhânta_ designates as the founder of astronomy, and who another treatise says was born at Romakapouri, "the city of the Romans."