Although Agni was said to have been begotten by the conjunction in the air of Varuna and Prihovi (Prithivi), all the principal gods, or Devas, originally conceived as the phenomena and power of heaven, were called the children of Dyaus and Prihovi, Agni and Indra being considered the two chief of the twelve Devas. Dyaus, Prihovi, and their progeny afterwards became endowed with moral qualities, and were looked upon as creators and governors of the world; and as time wore on the original Vedic deities gradually gave place to purely solar deities: the sun was called Surya, and differed from Agni, who was god of terrestrial and celestial fire—sun, lightning, and altar fire in one, the soul of universe, and mediator between the gods and men; Surya was also Savitri, the quickener, who in the early morn rouses the sleepers, and in the evening twilight buries them again in sleep; he is also Vishnu, the companion of Indra, who traverses the celestial space in three long strides; he is Pushan, the nourisher and faithful guide of men and animals; and he is Yama, who traverses the steep road to death and the shades. Thus the gods multiplied—the original supreme deity, Varuna, who was one with Indra, though different from him, giving place to a multitude of solar deities, children of Dyaus, the great dawn-god or day-father. As the old Vedic language became lost to the people there arose a custom of setting apart certain individuals to faithfully preserve the old and sacred records, and thus arose the priestly caste of Brahmans, whose duties consisted in transcribing the sacred hymns of the _Rig-Veda_ and preserving the knowledge of the sacred language in which they were first written. The great day-father, Dyaus, now received the name of Brahma, the magic power, and Prajapeti, the lord of creatures, and was endowed with three divine energies—Agni (fire), Vayu (air), and Surya (the sun), which together formed a subordinate triad. Soma became associated with the moon; Asura became the demon of hell, which was peopled with tormenting monsters; Indra and Vishnu became blended with Surya; and Rudra was converted into Siva and identified with Agni. As Brahmanism progressed the principal worship on the shores of the Ganges gradually centred round Vishnu, who was supposed to undergo periodically a number of Avataras, or incarnations, by means of which he rescued fallen man from the fate awaiting him. These descents to the lower world were very frequent, and appear to have had some connection with the zodiacal constellations; for we find the incarnation at one time taking place as a man, at another as a fish, at another as a lion, and so on.