pressure in stamping from that part that has been subjected to less. But, as already mentioned, all explanations depending on stamping must at the outset be put on one side when studying the behaviour of Japanese mirrors, since casting, and not stamping, is the process employed in their manufacture.

In the "Reader" (a paper now extinct) for February, 1866, Mr. Parnell attempts to explain the phenomenon by an inequality in the surface of the mirror, produced by the thinner portion warping more in cooling than the thicker part where the pattern exists, and he endeavours to experimentally examine this by studying the direct reflection. of the globe of a gas-lamp, as seen in the different parts of the mirror. We, as well as Professor Atkinson, have tried to repeat this experiment with some magic mirrors in our possession, but we cannot say that it affords any conclusive evidence regarding the cause of the phenomenon.

It therefore appeared to us a year ago that the subject would repay investigation, an opinion also expressed by Professor Silvanus Thompson, who, in writing from University College, Bristol, to "Nature," during June of 1877, suggested that the Japanese mirrors exhibited at the Loan Collection of Scientific Apparatus in London might, if they showed the phenomenon, be used for such an investigation. And as Professor Atkinson did not propose following up the question himself, he lent us the mirror which he possessed, and cordially agreed with our proposal that we should undertake the investigation. This we have done, and obtained the results which we venture to submit this evening to the Society.

At the commencement of the inquiry we naturally desired to see what had been written on the subject of Japanese mirrors, and this brought to our notice the information regarding mirrors generally in this country, which, as mentioned at the beginning of this paper, will form, we propose, the substance of a subsequent communication. But, of the magic mirror, Japanese literature (so far as we have been able to ascertain) makes absolutely no mention.

In "Les Industries Anciennes et Modernes de l'Empire Chinois," published in 1869, by MM. Stanislas Julien and Paul Champion, there is a short article on "Les Miroirs Magiques des Chinois, et leur fabrication," taken from the paper communicated by M. Julien to the French Academy of Sciences. In this he says:—

"Many famous philosophers have for a long time, but without success, endeavoured to find out the true cause of the phenomenon which has caused certain metallic mirrors constructed in China to have acquired the name of magic mirrors. Even in the country itself where they are made no European has, up to the present time, been able to obtain either from the manufacturers, or from men of letters, the information, which is so full of interest to us, because the former keep

it a secret when by chance they possess it, and the latter generally ignore the subject altogether. I had found many times in Chinese books details regarding this kind of mirrors, but it was not of a nature to satisfy the very proper curiosity of philosophers, because sometimes the author gave on his own responsibility an explanation that he had guessed at, and sometimes he confessed in good faith that this curious property is the result of an artifice in the manufacture, the monopoly of which certain skilled workmen reserve to themselves. One can easily understand this prudent reticence when we remember that the rare mirrors which show this phenomenon sell from ten to twenty times as dear as the rest."

M. Julien then gives an elaborate description of one of these mirrors in the possession of the Marquis de La Grange. He further remarks that such mirrors are called in Chinese theou-kouang-kién, which means literally "mirrors that let the light pass through them," and that this name has arisen from a popular error on the subject. Chin-kouo, a Chinese writer who flourished in the middle of the eleventh century, speaks with admiration about them in his memoirs called Mong-ki-pitân, book xix, folio 5. The poet Kin-ma has celebrated them in verse ; but up to the time of the Mongolian emperors nobody could explain the cause of the wonderful phenomenon. Ou-tseu-hing, who lived between 1260 and 1341 under this dynasty, had the honour of being the first to throw any light on the subject. He says:

"When we turn one of the mirrors with its face to the sun, and allow it to throw a reflection on a wall close by, we see the ornaments or the characters which exist in relief on the back appear clearly. Now the cause of this phenomenon arises from the employment of two kinds of copper of unequal density. If on the back of the mirror a dragon has been produced while casting it in the mould, then an exactly similar dragon is deeply engraved on the face of the disk. Afterwards the deep chisel-cuts are filled up with denser copper, which is incorporated with the body of the mirror, which ought to be of finer copper, by submitting the whole to the action of fire, then the face is planed and prepared, and a thin layer of lead or of tin spread over it.*

"When a beam of sunlight is allowed to fall on a polished mirror prepared in this way, and the image is reflected on a wall, bright and dark tints are distinctly seen, the former produced by the purer copper, and the latter by the parts in which the denser copper is inlaid."

If, then, we understand this description of Ou-tseu-hing correctly, it would appear that the pattern appears by reflection as a dark image on a bright ground, the opposite of what is experienced in Japanese mirrors.

* This probably refers to the mercury amalgam which is used in polishing, and which Ou-tseu-hing mistook for lead or tin.

Ou-tseu-hing adds that he has seen a mirror of this kind broken into pieces, and that he has thus ascertained for himself the truth of this explanation.

In a recent interesting article published in No. 29 of the “Gartenlaube," Heft 8, 1877, by the well-known German popular writer whose nom-de-plume is Carus Sterne, doubt is thrown on the above explanation, since Herr Sterne thinks the magic mirror he himself possesses is too thin for any such inlaying to have been performed. In quoting the information given by M. Julien, to which reference is made above, he incidentally mentions that it is taken from the fifty-sixth volume of the Chinese encyclopædia called "Ke-chi-king-youen." Herr Sterne adds that these magic mirrors were known to the Chinese from the earliest times, and that one of their writers spoke about them in the ninth century of the Christian era. He remarks that the Roman writer Aulus Gellius, who lived seventeen centuries ago, referred to mirrors that sometimes reflected their backs and sometimes did not. From the great antiquity of the Chinese magic mirrors Herr Sterne thinks it probable that the mirrors with secret signs and figures of imps on the back which formed a portion of the stock-in-trade of the witches of the middle ages were of Eastern manufacture. He further alludes to the account given by the Italian historian Muratori of the magic mirror found under the pillow of the Bishop of Verona, who was afterwards condemned to death by Martin della Scala, as well as to the one discovered in the house of Cola da Rienzi, on the back of which was the word "Fiorone."

Neither in "Les Memoires concernant les Chinois par les Missionaires," nor in Duhalde's classical work on China, is there any mention of the magic mirror. I understand, however, that a short paper on the subject, by Professor Harting, appeared some years ago in a Dutch periodical, the "Album der Naturer;" this I have not seen: but Dr. Geerts, a Dutch gentleman resident in Japan, and who has a most extensive acquaintance with the literature bearing on that country, informs me no explanation of the phenomenon was contained in that article.

46

Japanese literature, as already mentioned, appears to be quite barren of information regarding their own or the Chinese mirrors which appear to reflect their backs. But in the shim-pen-kamakura-shi, or 'New Collection of Writings about Kamakura," it is mentioned that in the temple Kenchoji, situated in the ancient capital of the Shogun,* there is treasured up a wonderful old mirror, 31⁄2 sūns high and 3 sūns wide,† which, when looked at somewhat obliquely, shows the image of

Shogun, the military usurper of the throne of Japan, and recognized in modern times prior to the revolution of 1869 as the rightful sovereign. He was sometimes erroneously called the Tycoon.

† A sun is nearly one and one-fifth of an inch.

VOL. XXVIII.

L

a Buddhist god. This appearance, however, is in no way connected with the pattern at the back, which consists of a new moon reflected in the sea; the artistic balance of the picture being maintained by a rosary and a plum tree. The hole in the upper portion of the mirror is probably for the attachment of a silk cord to hang it up by. The supposed marvellous character of this mirror causes great reverence to be shown to the god of the temple, as it is considered to furnish an undoubted proof of his supernatural character; in fact, the mirror receives nearly as much respect as this Buddhist deity himself. The way in which the optical effect has been produced is said to be the same as that described in the Kokon-i-to, "The Genealogy of the Old and New Physicians," and which is as follows:-Take ten parts of shio (gamboge), one of funso, and one of hosha (borax). Powder these thoroughly, and mix them to the consistency of a paste with a little dilute glue. If any pattern be drawn on the surface of the mirror with this paste, and then allowed to dry, the pattern will be seen, even after polishing, if looked at obliquely.

A mirror, in the face of which was seen the appearance of the famous priest, Shinran-sho-niu, who instituted the Shinshiu religion, to which the Honguangi temples at Kioto belong, was formerly in the possession of the Kuge* Rokujo, and was, to a certain extent, worshipped. Wood-cuts of this mirror were also sold at this nobleman's house, and were regarded as a faithful representation of the priest Shinran-sho-nin. One of the persons formerly employed at the Honguangi temples, Kioto, tells us he remembers, some years ago, a messenger, coming from Mr. Rokujo, asking that the authorities of the temple would give a certificate, stating that the mirror had been constructed by Shinran-sho-nin himself for holy purposes. This, however, they declined to do, believing rather that Mr. Rokujo had fabricated it himself to obtain money on exhibition. Mr. Rokujo, to whom we have applied on the subject, says, that the old tradition in his family was that the mirror originally came from Echigo ;t also that, after the failure to obtain a certificate of its sanctity referred to above, he sold it to a temple situated near Kioto, from which, however, it was subsequently removed, and that he is quite unacquainted with its present whereabouts.

A Tokio mirror maker, however, tells us that he has seen an exactly similar mirror at Okasaki-mura, a small village near Kioto, so perhaps this is the present habitation of Mr. Rokujo's old mirror.

It does not appear that this chemical method of preparing the face

Kuge," a nobleman formerly attached to the Micado's Court at Kioto, the ancient capital.

+ Echigo, a province in the centre of Japan.

"The Eastern Capital," the name given to Yedo since the revolution of 1869. when the Micado transferred his court there from Kioto.

has ever been employed in Japan to alter a portion of the surface in such a way that this part becomes visible in the image formed by reflection, although invisible when looked at directly. A certain Tokio mirror maker, however, said that he had employed the chemical method for this purpose in the following way :

Coat the surface of the mirror with urushi (Japanese varnish), with the exception of the portion that it is desired shall cast the brighter reflection, then act on this part with a paste composed of equal parts of sulphur and copper sulphate, powdered and mixed with shiro-umedzu (white plum acid). If this paste, after being allowed to dry on the mirror, which takes about two days, be rubbed off, and the mirror be frequently polished, the pattern (so said this mirror maker) will become invisible when looked at, but will appear in the reflection of the mirror thrown on to a screen. If the above be true, then, if a pattern be drawn on the face of the mirror with the varnish while the remainder of the face is acted on chemically, this pattern should, on reflection, appear darker than the rest. We therefore instructed him to prepare two mirrors, and on the face of one to act chemically on a portion corresponding with the letter "C," while, with respect to the other, he was to leave untouched only a small part of the face, corresponding with the letter "N." This he did; after several polishings of the two mirrors both letters could be seen, either directly or on reflection; after many polishings, however, the letter "C" disappeared for direct vision, but it also disappeared for reflection, and the letter "N" remained visible, either if looked at very obliquely, or when a bright light was reflected on to a screen. In other words, the attempt of this mirror maker turned out a failure. He regards it as resulting from a loss of his former skill, but we are inclined to think that he was confusing the method with which he was acquainted for making an image visible when the face of the mirror is looked at obliquely (the phenomenon which is observed in the mirror at Kamakura), with a method for making the so-called magic mirror, of which he has probably no knowledge. One very interesting fact, however, came out in this experiment, and that was the mirror on which the letter "C" was made, and which did not originally reflect the pattern on the back, acquired the power to do so after ten successive polishings. In fact, the mirror maker caused this mirror to acquire the so-called magic character, but in a way unexpected by himself.

Explanations:-The possible explanations of the phenomenon shown by certain Japanese mirrors may be divided into three classes:

1. The pattern might be scratched on the face of the mirror and hidden by subsequent polishing.

2. The portion of the face corresponding with the pattern might have a different molecular constitution from the metal forming the remainder of the mirror.