figures of 720,000 or 490,000 years set by Epigenes and Berosus and Critodemus for the duration of astronomical observations recorded by the Babylonians.[448] From such passages we get the impression that astrology is widely accepted as a science but that the art of nativities at least is not regarded by Pliny with favor. But it would not be safe to say that he denies the control of the stars over human destiny. Indeed, in one chapter he declares that the astronomer Hipparchus can never be praised enough because more than any other man he proved the relationship of man with the stars and that our souls are part of the sky.[449] When Pliny disputes the vulgar notion that each man has a star varying in brightness according to his fortune, rising when he is born, and fading or falling when he dies, he is not attacking even the doctrine of nativities; he is denying that the stars are controlled by man’s fate rather than that man’s life is ordered by the stars.[450] [Sidenote: Celestial portents.] If Pliny thus leaves us uncertain as to the relation of man to the stars, we also receive conflicting impressions from his discussion of various celestial phenomena regarded as portentous. In one passage he speaks of the debt of gratitude owed by mankind to those great astronomical geniuses who have freed men from their former superstitious fear of eclipses.[451] But he explains thunderbolts as celestial fire vomited forth from the planet Venus and “bearing omens of the future.”[452] He also gives instances from Roman history of comets which signaled disaster, and he expounds the theory of their signifying the future.[453] What they portend may be determined from the direction in which they move and the heavenly body whose power they receive, and more particularly from the shapes they assume and their position in relation to the signs of the zodiac. Indeed, Pliny even gives examples of ominous eclipses of the sun, although it is true that they were also of unusual length.[454] He also tells us that many of the common people still believed that women could produce eclipses “by sorceries and herbs.”[455] [Sidenote: The stars and the world of nature.]