Strange to say, a similar mistranslation occurs in Dr. Hirth's short but excellent treatise on _Ancient Chinese Porcelain_,[309] in a passage which is nevertheless of great importance to our quest. It has been the custom with Chinese compilers of reference works to incorporate the material of previous editions, adding their own commentaries and any further information which happened to have reached them, and to this we are indebted for the preservation of many passages from ancient writers which would otherwise be extremely difficult of access. Thus Hirth found embalmed in the Sung Pharmacopœia two early references to the material _pai o_ [Chinese] which he shows to be without doubt the kaolinic earth used in the manufacture of porcelain, and which, like many other strange materials, entered into Chinese medicinal prescriptions. The first mention of this substance is taken from the writings of T´ao Yin-chü, who died in 536 A.D., to the effect that the _pai o_, besides being used in medicines, was employed at that time for painting pictures; and Hirth argues that so celebrated a writer on scientific subjects as T´ao Yin-chü could not have failed to note it if the _pai o_ had been in general use for ceramic purposes as well. This is followed by a quotation from the T´ang Pharmacopœia (compiled about 650 A.D.): "It (_pai o_) is now used for painter's work, and rarely enters into medicinal prescriptions; during recent generations it has been prepared from white ware[310] (_tz´ŭ_)." By rendering the last sentence "during recent generations it has been used to make white porcelain," Hirth invested the passage with a greater interest than it actually possesses. But even when stripped of this fictitious importance, it constitutes the first literary evidence we have of the use of kaolin by Chinese potters. This is followed by another quotation from the T´ang Pharmacopœia recommending for medicinal purposes a powder prepared from the white ware of Ting Chou.[311] Whether we are to understand that the Chinese pharmacist ground up broken pieces of Ting ware or merely made use of the refined and purified clay obtained at the potteries, matters little. Neither proceeding would be without parallel in Europe in far later times than the T´ang period. But the specific reference to white Ting ware at this early date is most interesting in view of the fact that Ting Chou was celebrated in the Sung dynasty for a white ware which is undoubtedly a kind of porcelain.