Later, it is actually called the celestial river and we are further told that the land of the blessed is to be reached by "the celestial ship with a good rudder." We can satisfactorily account for these legends by supposing that the Vernal equinox was near the Dog-star in those days just near the Milky Way.
There is another set of traditions which can be similarly explained on the supposition with which we have started, viz., the Vernal equinox was then in Orion. The heliacal rising of the constellation at the beginning of the year marked the revival of nature at the commencement of spring and the asterism may thus be said to represent all these milder influences which in later mythology were fully embodied in the conception of Vishnu. But the case was completely reversed if we take the acronycal rising of the same. It was at the autumnal equinox that the Dog-star rose at the beginning of night and though strictly speaking it marked the end of Varsha,yet the portion of the heaven wherein the constellation is situated could have been easily regarded as the battle-ground of Indra and Vritra, who fought in those days and also as the stage on which the terrible Rudra made his appearance. On this same hypothesis we can explain how Vritra came to be stationed at the gates of hell. Indra cut oH the head of Vritra or Namuchi in the form of a Mriga and this at once suggests whether that head is not the same as that of Prajapati cut off by Rudra (Ardra or Sirius). The foamy weapon with which Indra killed Namuchi is nothing but a reference tot he Milky Way, The attributes of Rudra, chasing of the antelope, his bearing of the Ganges in his matted hair and fondness for the burning ground
