Almost irresistibly, as it appears to me, the conviction forces itself on the mind, in considering the position held by the constellation Hydra 4,000 B.C., that it was at that date that this baleful figure was first traced in imagination on the sky, there fitly to represent the power of physical (and may we not suppose also, of moral?) darkness--a great and terrible power--but a power ever and ever again to be conquered by the victorious power of light. In astronomic myth this power was represented as that of the sun at the season of its highest culmination, the season of the summer solstice. For an observer in the temperate northern zone all through the long nights of mid-winter, the whole length of the dreadful Hydra was at the date named visible above the horizon. The dark midwinter season was therefore the time of the Hydra’s greatest glory. At every season of the year, except at that of midsummer, some portion of the monster’s form was visible during some part of the night. But at the summer solstice no star in the constellation might show itself for ever so short a time.[58] [58] Plate IX. represents the constellations above the horizon, _but invisible at noon at the midsummer solstice_. It therefore represents those above the horizon, _and visible at midwinter midnight_. [Illustration: PLATE IX. Position of the Sun amongst the Constellations at Summer Solstice, 4,000 B.C. Observer in Lat. 40° N. Constellations between the lines H Z and Z H invisible all through the night of Summer Solstice. [_To face p. 118._] The supposed latitude of the observer in Plate IX. is 40° N., a latitude considerably to the north of any part of India; but it is to be remembered that the Indra-Vritra myth cannot be claimed with any certainty as a purely and originally Indian myth, for, as Macdonell points out (as quoted above), there is a probability that “the Indo-Iranian period possessed a god approaching to the Vedic form of the Vrtra-slaying Indra,” and that “it is even possible that beside the thundering god of heaven, the Indo-European period may have known as a distinct conception a thunder-god, gigantic in size, a mighty eater and drinker, who slays the dragon with his lightning bolt.”[59] [59] V. p. 114. For the _origin_ of this world-wide myth, therefore, we should not look to the tropical Indian Zone; but it is in Indian latitudes that we should look for an explanation of the physical phenomena _hymned by Vedic bards in the distinctly Indian development of the Indra-Vritra myth_. I believe that in thus tracing the course of the Indra story from temperate to tropical latitudes, we shall find a reason for the contradictory attributes assigned to the demon Vritra, namely those of darkness and drought.