An interesting passage in the first letter[293] of Père d’Entrecolles describes a curious kind of porcelain, of which the secret had already been lost. It was known as _chia ch’ing_ or “blue put in press,” and it was said that the blue designs on the cups so treated were only visible when the vessel was filled with water. The method of the manufacture is described as follows: “The porcelain to be so decorated had to be very thin; when it was dry, a rather strong blue was applied, not to the exterior in the usual manner, but on the interior to the sides. The design usually consisted of fish, as being specially appropriate to appear when the cup was filled with water. When the colour was dry a light coating of slip, made with the body material, was applied, and this coating enclosed the blue between two layers of clay. When this coating was dry, glaze was sprinkled inside the cup, and shortly afterwards the porcelain was placed on the wheel. As the body had been strengthened on the interior, the potter proceeded to pare it down outside as fine as possible without actually penetrating to the colour. The exterior was then glazed by immersion. When completely dry it was fired in the ordinary furnace. The work is extremely delicate, and requires a dexterity which the Chinese seem no longer to possess. Still, they try from time to time to recover the secret of this magical painting, but without success. One of them told me recently that he had made a fresh attempt, and had almost succeeded.” No example of this mysterious porcelain is known to exist, and it is probable that the whole story is based on some ill-grounded tradition. It is true that water will bring out the faded design on certain old potteries, but this is due to the action of the water in restoring transparency to a soft decayed glaze. But how the water or any other liquid could affect the transparency of a hard, impenetrable porcelain glaze, still less influence the colour concealed beneath a layer of clay and glaze, is far from clear. Indeed, the whole story savours of the “tall tales” quoted in chap. x. of vol. i. But perhaps it will not be inappropriate to mention here another peculiar type of blue and white, which, if we may judge by the early date mark usually placed upon it, throws back to some older model. The design, usually a dragon, is delicately traced with a needle point on the body of the ware, and a little cobalt blue is dusted into the incisions.[294] The glaze is then applied, and when the piece is fired and finished the dragon design appears faintly “tattooed” in pale blue. The effect is light and delicate, but of small decorative value, and the few examples which I have seen are redeemed from insignificance by a peculiarly beautiful body of pure glassy porcelain. They bear an apocryphal Ch’êng Hua mark, but evidently belong to the first half of the eighteenth century, to the Yung Chêng, or perhaps the late K’ang Hsi period.