The relationship of the Matsya Purana to the great epic and its supplementary book as sources is similarly intimate. It is introduced with the story of Manu and the Fish (Matsya). The Kurma, besides giving an account of the various Avatars of Vishnu (of which the tortoise or kurma is one), of the genealogies of gods and kings, as well as other matters, contains an extensive account of the world in accordance with the accepted cosmological notions of the Mahabharata and of the Puranas in general. The world is here represented as consisting of seven concentric islands separated by different oceans. The central island, with Mount Meru in the middle, is Jambu-dvipa, of which Bharata-varsha, the "kingdom of the Bharatas," or India, is the main division. The Markandeya, which expressly recognises the priority of the Mahabharata, is so called because it is related by the sage Markandeya to explain difficulties suggested by the epic, such as, How could Krishna become a man? Its leading feature is narrative and it is the least sectarian of the Puranas. The extensive Padma Purana, which contains a great many stones agreeing with those of the Mahabharata, is, on the other hand, strongly Vishnuite in tone. Yet this, as well as the Markandeya, expressly states the doctrine of the Tri-murti or Trinity, that Brahma, Vishnu, and Çiva are only one being. This doctrine, already to be found in the Harivamça, is not so prominent in post-Vedic literature as is commonly supposed. It is interesting to note that the story of Rama, as told in the Padma Purana, follows not only the Ramayana but also Kalidasa's account in the Raghuvamça, with which it often agrees literally. Again, the story of Çakuntala is related, not in accordance with the Mahabharata, but with Kalidasa's drama. The Brahma-vaivarta Purana is also strongly sectarian in favour of Vishnu in the form of Krishna. It is to be noted that both here and in the Padma Purana an important part is played by Krishna's mistress Radha, who is unknown to the Harivamça, the Vishnu, and even the Bhagavata Purana. The Vishnu Purana, which very often agrees with the Mahabharata in its subject-matter, corresponds most closely to the Indian definition of a Purana, as treating of the five topics of primary creation, secondary creation, genealogies of gods and patriarchs, reigns of various Manus, and the history of the old dynasties of kings. The Bhagavata Purana, which consists of about 18,000 çlokas, derives its name from being dedicated to the glorification of Bhagavata or Vishnu. It is later than the Vishnu, which it presupposes, probably dating from the thirteenth century. It exercises a more powerful influence in India than any other Purana. The most popular part is the tenth book, which narrates in detail the history of Krishna, and has been translated into perhaps every one of the vernacular languages of India.