The _Cho kêng lu_[133] refers to three minor wares which were regarded as inferior to Kuan ware, and later writers have assumed that they belonged to the same category. These are the Hsü wares, Yü-hang wares, and _wu-ni_ wares. The first[134] is so little known that its identity has been lost in variant readings, such as Hsün [Chinese] in later writers, which is very near in appearance to _tung_ [Chinese], a common form used for the Tung ware (see p. 82); and we can safely leave it until some clearer information is forthcoming. The second, according to the _T´ao lu_,[135] was a Sung ware made at Yü-hang Hsien, in the prefecture of Hang Chou. "Its colour was like Kuan porcelain without its crackle, its lustre (_jung_), and its unctuous richness (_jun_)." The _wu-ni_ ware is dark-bodied earthenware, which is discussed on p. 133. [Illustration: Fig. 1 Fig. 2 Plate 18.--Sung dynasty. Fig. 1.--Bowl with engraved peony design under a brownish green celadon glaze. Northern Chinese. Diameter 7¾ inches. _Eumorfopoulos Collection._ Fig. 2.--Vase moulded in form of a lotus flower, dark grey stoneware, burnt reddish brown, milky grey glaze, closely crackled. Height 7 inches. _Freer Collection._] _Ko yao_ [Chinese] _Ko yao_ (the elder brother's ware), or _Ko ko yao_, as it is sometimes called with the first character repeated, is unanimously ranked by Chinese writers with the Ju and Kuan wares. According to the traditional accounts, it was first made by the elder of the two brothers Chang [Chinese], who were potters of Lung-ch´üan Hsien in the Ch´u-chou Fu, province of Chekiang, each having a separate factory in the Liu-t´ien district. Most of the Chinese authorities are content to give the date of these brothers as some time in the Sung dynasty, but one account[136] narrows the period down to the Southern Sung (1127-1279 A.D.). Professor Hirth takes the rationalistic view that the story of the brothers is a myth embodying the fact that there were two distinct types of ware made in the Lung-ch´üan district. Be this as it may, the Ko yao is of considerable interest to us as forming a link between the obscure Ju and Kuan wares and the well-known Lung-ch´üan celadon, approaching the latter in its grass green and sea green varieties and the former in its most highly prized specimens of bluish green or grey tones.