The presence of a kaolin-like material in a dark-coloured ware, probably of the third century, which was disclosed by the analysis made by Mr. Nicholls in Chicago, has already been recorded (p. 15). We have no means of ascertaining what length of time elapsed before a white material of this nature was evolved, but it was clearly in existence in the beginning of the sixth century. Possibly it was not porcelain according to the strict European definition, but there is every reason to suppose that it was a hard white ware, such as the Chinese would not hesitate to include in their porcelain category. Such a ware appears on some of the funeral vases which may safely be referred to the early T´ang period (see p. 26), and in default of other evidence I think we can say that porcelain in the Chinese sense already existed at the end of the Sui dynasty.[312] Though this period happens to coincide with the lifetime of Ho Ch´ou, neither his name nor any other has been associated with the event by the Chinese, and it is highly probable that porcelain only came into being by a process of evolution from pottery and stoneware, the critical moment arriving with the discovery of deposits of kaolinic earth. As a mere speculation, I would suggest that the deposits were those at Han tan, the modern Tz´ŭ Chou, which supplied material for the Ting Chou potters.[313] It is, at any rate, significant that the new name, which we are led to suppose was derived from the _tz´ŭ_ stone,[314] was given to that place in the Sui dynasty. Numerous literary references from this time onwards have already been quoted which are highly suggestive of porcelain. The "false jade vessels" of T´ao Yü in the early years of the seventh century; the eighth-century tea bowls of Yu Chou and Hsing Chou which were compared respectively to jade and ice, to silver and snow, the former being green and the latter white. The twelve cups used for musical chimes by Kuo Tao-yüan; the white bowls immortalised by the poet Tu "of ware (_tz´ŭ_) baked at Ta-yi, light but strong, which gives out a note like jade when struck."