Nats are of at least three classes, or rather have three origins. Firstly they are nature spirits, similar to those revered in China and Tibet. They inhabit noticeable natural features of every kind, particularly trees, rivers and mountains; they may be specially connected with villages, houses or individuals. Though not essentially evil they are touchy and vindictive, punishing neglect or discourtesy with misfortune and ill-luck. No explanation is offered as to the origin of many Nats, but others, who may be regarded as forming the second category, are ghosts or ancestral spirits. In northern Burma Chinese influence encouraged ancestor worship, but apart from this there is a disposition (equally evident in India) to believe that violent and uncanny persons and those who meet with a tragic death become powerful ghosts requiring propitiation. Thirdly, there are Nats who are at least in part identified with the Indian deities recognized by early Buddhism. It would seem that the Thirty Seven Nats, described in a work called the Mahâgîtâ Medânigyân, correspond to the Thirty Three Gods of Buddhist mythology, but that the number has been raised for unknown reasons to 37[174]. They are spirits of deceased heroes, and there is nothing unbuddhist in this conception, for the Piṭakas frequently represent deserving persons as being reborn in the Heaven of the Thirty Three. The chief is Thagyâ, the Śakra or Indra of Hindu mythology[175], but the others are heroes, connected with five cycles of legends based on a popular and often inaccurate version of Burmese history[176]. Besides Thagyâ Nat we find other Indian figures such as Man Nat (Mâra) and Byammâ Nat (Brahmâ). In diagrams illustrating the Buddhist cosmology of the Burmans[177] a series of heavens is depicted, ascending from those of the Four Kings and Thirty Three Gods up to the Brahmâ worlds, and each inhabited by Nats according to their degree. Here the spirits of Burma are marshalled and classified according to Buddhist system just as were the spirits of India some centuries before. But neither in ancient India nor in modern Burma have the devas or Nats anything to do with the serious business of religion. They have their place in temples as guardian genii and the whole band may be seen in a shrine adjoining the Shwe-zi-gon Pagoda at Pagan, but this interferes no more with the supremacy of the Buddha than did the deputations of spirits who according to the scriptures waited on him. 4