In addition to the Lung-ch´üan and Ch´u-chou celadons, which are readily recognised by their peculiar glaze and their reddish brown foot rims, there are many other kinds which are not easy to classify. Some of these have a dry, buff stoneware body and brownish green glaze, while others have a glaze of decided grey or blue grey tone. In conjecturing the origin of these we must take into consideration the private factories which existed under the Northern Sung at Ch´ên-liu[168] and other localities in the neighbourhood of the eastern capital (_tung ching_), now named K´ai-fêng Fu, in Honan. The _Ko ku yao lun_[169] describes the ware of these parts under the heading _Tung yao_[170]: "It is pale green (_ch´ing_) in colour, with fine crackle, and in many cases has a brown mouth and iron foot. Compared with Kuan ware it lacks the red tinge, and its material is coarse, wanting in fineness and lustre, and far from equalling that of the Kuan ware. At the present day (i.e. 1887) it is rarely seen." Other writers repeat this passage with little alteration, though the author of the _T´ao lu_ adds that the clay was of black colour and the glaze of varying depth. Hsiang's Album includes one specimen of the _tung ch´ing tz´ŭ_, describing the colour as _t´ieh ts´ui_, which probably means the blue green shade of distant hills.[171] _Tung ch´ing_ glaze is included in the list of those imitated in the Imperial factories about 1780, two kinds, pale and deep, being specified; and the _T´ao lu_[172] informs us that the _Tung ch´ing_ was copied to a considerable extent at Ching-tê Chên in the early nineteenth century, and that the modern glaze was exactly like the old. That this modern glaze was only a variety of celadon is shown by the recipe given in the same work,[173] viz. "to add to the ordinary glaze some of the mixture containing ferruginous earth," which differs from that given for the modern Lung-ch´üan glaze only in the absence of the pinch of cobalt (see vol ii., p. 189). A verse from a poem by Chang-lei (1046-1106) indicates the green colour of the ware: "Green jade (_pi yü_) when carved makes a vessel; know it to be the porcelain (_tz´ŭ_) of the Tung kilns [Chinese]."[174]