M. STANISLAS JULIEN, the erudite author of Les Industries anciennes et modernes de l’empire chinois, has given the following extract from the fifty-sixth volume of the Chinese encyclopædia called Ke-chi-king-yonen.
“Théou-kouang-kien, or Mirrors which let the light pass through (an expression due to a vulgar error). If one receives the rays of the sun upon the polished surface of one of these mirrors, the characters or flowers which are in relief on the back are reproduced faithfully in the (reflected) image of the disk. Chin-kouo (a writer who flourished in the middle of the eleventh century) speaks with admiration of them in his memoirs entitled Mong-ki-pi-tân, book xix., fol. 5. The poet Kin-ma celebrated them in verse; but, down to the time of the Mongolian emperors, no author had been able to explain this phenomenon. Ou-tseu-hing, who lived under this dynasty (between 1260 and 1341), has the merit of having first done so. This is how he expresses himself on this subject:
“‘When one places one of these mirrors facing the sun, and causes it to reflect, upon a very near wall, the image of its disk, one sees distinctly appear therein the ornaments or characters which exist in relief upon the back. Now the cause of this phenomenon, which arises from the distinct employment of fine copper and of crude copper. If on the back of the mirror one has produced, by casting it in a mould, a dragon arranged within a circle, one engraves deeply on the face of the disk an exactly similar dragon. Next, one fills the deeply-chiselled cuts with a somewhat baser copper; then one incorporates this metal with the first, which ought to be of a finer quality, by submitting the mirror to the action of fire; after which one flattens and smoothens down the face of the mirror, and spreads over it a slight layer of lead (tin?).
“‘When one turns toward the sun the polished disk of a mirror so prepared, and reflects its image upon a wall, it distinctly presents bright tints and dark tints, which come, these from the purest parts of the copper, those from the baser parts.’
“Ou-tseu-hing, to whom we owe the preceding explanation, tells us that he has seen a mirror of this sort broken into fragments, and that he recognized for himself the accuracy of his description.”
Ayrton quotes from a Japanese work, the Shim-pen-kamakura-shi, or New Collection of Writings about Kamakura, a description of a temple-mirror, which when looked at obliquely shows the face of a Buddhist priest, not resembling in the least the raised ornament on the back (see p. 45, supra).
The same authority refers to the Kokon-i-to, or Genealogy of the Old and New Physicians, for an alleged process of producing magic effects on mirrors by treating the surface with a peculiar paste. The recipe is as follows: “Take ten parts of shio (gamboge), one of funso, and one of hosha (borax). Powder them thoroughly, and mix them to the consistency of a paste with a little dilute glue. If any pattern be drawn on the surface of a mirror with this paste, and then allowed to dry, the pattern will be seen, even after polishing, if looked at obliquely.”
It appears that this process fails in reality to give any result. The process of inlaying described by Ou-tseu-hing is also an error. The magic effect is certainly not produced in this way. Probably he was misled by the circumstance that flaws in the bronze castings are sometimes filled by the insertion of soft copper beads.