The district of Lung-ch´üan in the prefecture of Ch´u-chou, province of Chekiang, was noted for its potteries as early[154] as the beginning of the Sung dynasty, but its greatest celebrity was attained by the market town of Liu-t´ien, where the Chang brothers are reputed to have worked.[155] The story that the elder Chang moved to Liu-t´ien while the younger brother remained at Lung-ch´üan is, I believe, based on a misreading of a Chinese passage,[156] the true meaning of which seems to be that while the elder brother made new departures which earned for his ware the distinctive name of Ko yao, the younger continued the Lung-ch´üan traditions, and consequently his ware was known as Lung-ch´üan yao. It appears that one vital difference between the two wares was crackle, which was used by the elder and not by the younger brother. The productions of the Lung-ch´üan district are variously named in the _Ko ku yao lun_, "_Ch´u_ ware" (from Ch´u-chou Fu, the name of the prefecture), "_ch´ing_ ware," and "old _ch´ing_ ware," and the various Chinese accounts agree in distinguishing two broad classes, the one having a thin body of fine material, and the other a thick body of coarser and heavier make. The first of these two classes includes the Chang yao, or ware of the younger Chang, of which the _Ch´ing pi ts´ang_ gives the following description: "There is one kind in the manufacture of which white clay is used, and the surface of the ware is covered with _ts´ui_[157] glaze through which the white shows in faint patches. This is what was made by the Chang family in the Sung dynasty, and is called Chang yao. Compared with the Lung-ch´üan ware in style and make, it gives the impression of greater delicacy and refinement." Another writer[158] describes it as "single-coloured and pure, like beautiful jade, and ranking with the Kuan yao; whereas the Ko yao was pale in colour." The eleven examples figured and described in Hsiang's Album are all apparently of this class, and their colour is variously described as "green, of jade-green tint (_ts´ui pi_), like a wet, mossy bank or slender willow twigs," "green like the green of onion (sprouts)" (_ts´ui jo ch´ing ts´ung_), "green like parrot's feathers," "green like the dull green (_lü_) of a melon," and "soft jade-green like onion sprouts in autumn." Hsiang's similes leave no doubt as to the prevailing tint of the ware, which clearly aimed at rivalling the tint of the prized green jade. As might be expected, few if any of Chang's celadons are to be found in our collections. Relatively few in numbers, assuming them to have been the work of one lifetime, and slender in structure, it is improbable that many of them can have survived the chances of eight or nine hundred years, and even supposing that any of them have reached Europe, their identity now could only be a matter of conjecture.