These incarnations are called Avatars, or descendings, and form an important part of Hindu epic poetry. Of the ten Avatars which are attributed to Vishnu, nine have already taken place; the last is yet to come, when the god shall descend again from heaven, to destroy the present world, and to restore peace and parity. The three forms of the Deity, emanating mutually from each other, are expressed by the three symbols, A U M, three letters in Sanskrit having but one sound, forming the mystical name _Om_, which never escapes the lips of the Hindus, but is meditated on in silence. The predominant worship of one or the other of these forms constitutes the peculiarities of the numerous sects of this religion. There are other inferior divinities, symbols of the forces of nature, guardians of the world, demi-gods, demons, and heroes, whose worship, however, is considered as a mode of reaching that divine rest, immersion and absorption in Brahm. To this end are directed the sacrifices, the prayers, the ablutions, the pilgrimages, and the penances, which occupy so large a place in the Hindu worship. 3. CHARACTERISTICS OF THE LITERATURE AND ITS DIVISIONS.--A greater part of the Sanskrit literature, which counts its works by thousands, still remains in manuscript. It was nearly all composed in metre, even works of law, morality, and science. Every department of knowledge and every branch of inquiry is represented, with the single exception of history, and this forms the most striking general characteristic of the literature, and one which robs it of a great share of worth and interest. Its place is in the intellectual rather than in the political history of the world. The literary monuments of the Sanskrit language correspond to the great eras in the history of India. The first period reaches back to that remote age, when those tribes of the Aryan race speaking Sanskrit emigrated to the northwestern portion of the Indian Peninsula, and established themselves there, an agricultural and pastoral people. That was the age in which were composed the prayers, hymns, and precepts afterwards collected in the form of the Vedas, the sacred books of the country. In the second period, the people, incited by the desire of conquest, penetrated into the fertile valleys lying between the Indus and the Ganges; and the struggle with the aboriginal inhabitants, which followed their invasion, gave birth to epic poetry, in which the wars of the different races were celebrated and the extension of Hindu civilization related. The third period embraces the successive ages of the formation and development of a learned and artistic literature. It contains collections of the ancient traditions, expositions of the Vedas, works on grammar, lexicography, and science; and its conclusion forms the golden age of Sanskrit literature, when, the country being ruled by liberal princes, poetry, and especially the drama, reached its highest degree of perfection.