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CHINA
which had long before this time been employed in Western Asia in the decoration of pottery." There is no apparent reason to suppose that the nature of this "Mohammedan blue" (Hui-ching), as it was called, had undergone any change between the tenth and the fifteenth centuries. A more reasonable hypothesis is that improved methods of treating it were among the scientific and technical developments for which the Ming epoch was remarkable. Dr. Bushell has the following note on the subject:—
The blue colour used for painting under the glaze was originally brought from one of the Mohammedan countries on the West of China as tribute, according to the Official Description of the Province of Kiangsi. In the reign of Hsuan-té (1426-1435) it was called Su-ni-po blue, and it is recorded that the supply of it faded before the reign of Chéng-hua (1465-1487). In other books of the period it is called Su-ma-li, or Su-ma-ni, blue. In the reign of Chia-ching (1522-1567) Mohammedan blue was again obtained by a eunuch governing the province of Yunnan, and the blue-and-white of this reign is still celebrated for its brilliant colour. The supply again ran short towards the end of this reign, and an inferior blue was produced from the incineration of Wu-ming-yi, a cobaltiferous ore of manganese found in different parts of China. The Mohammedan blue was broken up with the hammer, and the pieces which showed on fracture vermilion spots were picked out as the first-class blue, those with silver stars being used for the medium colour, and from each sixteen ounces of these pieces three ounces remained after the incineration in a closed vessel. The remaining fragments were thrown into water, impurities drawn off by magnetic iron ore, and the residue yielded another thirtieth part by weight of the true blue. If this blue were employed alone the colour was apt to spread, and it was necessary to add a proportion of native blue, not too much or the colour would be dull and heavy. The "first-class blue" was a mixture of ten parts of the
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