extracts was altered as little as possible, so that the general result retains in a sense the value of an original source. In its arrangement the _Shih Chi_ became a model for all later historians: the first part is in the form of annals, and there follow tables concerning the occupants of official posts and fiefs, and then biographies of various important personalities, though the type of the comprehensive biography did not appear till later. The _Shih Chi_ also, like later historical works, contains many monographs dealing with particular fields of knowledge, such as astronomy, the calendar, music, economics, official dress at court, and much else. The whole type of construction differs fundamentally from such works as those of Thucydides or Herodotus. The Chinese historical works have the advantage that the section of annals gives at once the events of a particular year, the monographs describe the development of a particular field of knowledge, and the biographical section offers information concerning particular personalities. The mental attitude is that of the gentry: shortly after the time of Ssŭ-ma Ch'ien an historical department was founded, in which members of the gentry worked as historians upon the documents prepared by representatives of the gentry in the various government offices. In addition to encyclopaedias and historical works, many books of philosophy were written in the Han period, but most of them offer no fundamentally new ideas. They were the product of the leisure of rich members of the gentry, and only three of them are of importance. One is the work of Tung Chung-shu, already mentioned. The second is a book by Liu An called _Huai-nan Tzŭ_. Prince Liu An occupied himself with Taoism and allied problems, gathered around him scholars of different schools, and carried on discussions with them. Many of his writings are lost, but enough is extant to show that he was one of the earliest Chinese alchemists. The question has not yet been settled, but it is probable that alchemy first appeared in China, together with the cult of the "art" of prolonging life, and was later carried to the West, where it flourished among the Arabs and in medieval Europe.