are RV 6.61, RV 7.95 and RV 7.96. As a river goddess, she is described as a mighty flood, and is clearly not an earthly river. According to Michael Witzel, superimposed on the Vedic Sarasvati river is the heavenly river Milky Way, which is seen as "a road to immortality and heavenly after-life." The description of the Sarasvati as the river of heavens, is interpreted to suggest its mythical nature. In 10.30.12, her origin as a river goddess may explain her invocation as a protective deity in a hymn to the celestial waters. In 10.135.5, as Indra drinks Soma he is described as refreshed by Sarasvati. The invocations in 10.17 address Sarasvati as a goddess of the forefathers as well as of the present generation. In 1.13, 1.89, 10.85, 10.66 and 10.141, she is listed with other gods and goddesses, not with rivers. In 10.65, she is invoked together with "holy thoughts" () and "munificence" (), consistent with her role as a goddess of both knowledge and fertility. Though Sarasvati initially emerged as a river goddess in the Vedic scriptures, in later Hinduism of the Puranas, she was rarely associated with the river. Instead, she emerged as an independent goddess of knowledge, learning, wisdom, music and the arts. The evolution of the river goddess into the goddess of knowledge started with later Brahmanas, which identified her as Vāgdevī, the goddess of speech, perhaps due to the centrality of speech in the Vedic cult and the development of the cult on the banks of the river. It is also possible to postulate two originally independent goddesses that were fused into one in later Vedic times. Aurobindo has proposed, on the other hand, that "the symbolism of the Veda betrays itself to the greatest clearness in the figure of the goddess Sarasvati ... She is, plainly and clearly, the goddess of the World, the goddess of a divine inspiration ...". Other Vedic texts In post-Rigvedic literature, the disappearance of the Sarasvati is mentioned. Also the origin of the Sarasvati is identified as Plaksa Prasravana (Peepal tree or Ashwattha tree as known in India and Nepal). In a supplementary chapter of the Vajasaneyi-Samhita of the Yajurveda (34.11), Sarasvati is mentioned in a context apparently meaning the Sindhu: "Five rivers flowing on their way speed onward to Sarasvati, but then become Sarasvati a fivefold river in the land." According to the medieval commentator Uvata,