Silvanus P. Thompson

“ Engineers are so familiar with the circumstance that when metal castings are rapidly cooled the internal parts are in a state of strain, that they are not astonished to find that after a casting has been surfaced accurately on one face the figure may alter slightly by the mere release of internal strains in the slow annealing of time. It is quite possible [43] that this too occurs with Japanese mirrors, and that some of them may acquire with the mere lapse of time magic qualities that they do not show at first when newly polished. ”

“ Makers of mirrors and lenses for large telescopes are accustomed to test the perfection of their figure by a process known as Foucault’s, in which the observer, after allowing light to fall from a single well-defined point upon the (concave) mirror at nearly normal incidence, places his eye at the point where the reflected rays converge to a focus, and then sees the whole surface of the mirror uniformly bright, save only such spots as differ in curvature from the rest. ”

“ By holding a magic mirror very obliquely to the light one can discern traces of the pattern in the face, especially if one is accustomed to examine optical surfaces for small inequalities of curvature. ”

“ Some hold that the Japanese imperial crest, the kiku, which resembles a flower with sixteen petals joined and rounded at the outer extremities, and issuing from a small central disk, is also a blazon of the sun; others hold it to [12] represent the chrysanthemum. In Japanese pictures of the sun-goddess myth, the mirror is always represented as of the eight-point form. Tradition states that the flaw still to be seen in its surface was caused by a blow it received when the gods thrust it into the half-opened doorway of the rocky cavern as the sun-goddess peeped out. ”

“ Mendenhall was followed by two Japanese observers,—both trained in physical research in Europe,—Goto and Muraoka, the latter of whom, while confirming the main propositions that the effects are due to differences of convexity, and that the convexity is acquired during the process of mege or scoring over with the megebo, gave some further details learned from the mirror-makers of Tokio. He showed that any plate, if thin enough, whether of bronze, brass, copper, lead, zinc, iron, or glass, acquires the property of convexity on being scored over with scratches ”

“ Thicker mirrors are sometimes pared down with a knife to the convex shape: they seldom or never show magic properties. The knife is also used to pare down any portion which in the operation mege may have become too convex. The convexity is tested from time to time by applying a concave wooden form. Professor Ayrton was of opinion that the magic properties were conferred during the operation of scraping with the megebo, the thicker parts of the mirror yielding less, and therefore being polished down more than the thinner parts. ”

“ The whole phenomenon is explained if once it could be established that the surface over the thick [26] parts is flatter (less convex, or even actually slightly concave) than the surface over the thin parts. Using a large convex lens to converge sunlight that had been reflected from a mirror, they showed that by merely altering the distance of the screen on which the image was received they could make the image either positive or negative at will; a result impossible on any other hypothesis than that of differences of curvature of surface. ”

“ Mirror castings when they are removed from the mould are roughly flat on the face, and need to be subjected to several processes to finish their reflecting surfaces: during these processes they acquire their characteristic convexity and their high polish. The mirror is laid down on its back on a wooden board, and then scraped or scratched with a rounded iron rod about a foot long, called a megebo (“distorting rod”) . The process of scoring [29] over with the blunt tool is called mege. After being scored all over with scratches in every direction, it is found to be convex. ”

“ The investigators then, having procured some good mirrors, proceeded to test the various possible suggestions as to the origin, such as the supposed difference of density, or of molecular constitution, or the supposed inlaying of the face with inferior metal, or to supposed concealed scratches on the surface, or, finally, to differences of curvature. By simple experiments in which bright light was caused successively to fall upon the mirror in diverging, parallel, or converging beams, it was demonstrated beyond question that the last-named cause was the true one. ”

“ The mirror of old Japan is however a very different article from that known in modern Europe as a mirror. European mirrors are [14] made, as everyone knows, of glass silvered at the back. Japanese mirrors are invariably made of metal, the bronze employed being a compound of copper and tin, with traces of antimony or lead. ”

“ He also noted that if the face was scored by the megebo with parallel lines in one direction only, the convexity acquired was cylindrical. His conclusion was: “It appears then that [30] the magic of the Eastern mirror results from no subtle trick on the part of the maker, from no inlaying of other metal, or hardening of portions by stamping, but merely arises from the natural property possessed by thin bronze of buckling under a bending stress, so as to remain strained in the opposite direction after the stress is removed. ”

“ On removing the pressure it was found to retain permanently all the qualities of a good magic mirror, though it is slightly more convex than mirrors ordinarily are. Since then it has been found that many mirrors which, when purchased, showed no magic properties, can be converted into magic mirrors, some by application of screw pressure, some by mere bending by hand over the knee, some by burnishing under pressure the pattern at the back. ”

“ Another variety of the same experiment is to place a ruled diffraction-grating of 100 lines to the inch (ruled in a silvered surface on glass) close to a bright light, and with a short-focus lens project the lines upon a screen. Then interpose the magic mirror to throw the luminous lines upon another screen, when they will be seen with the usual magic image; the bright lines concentrating into the bright parts and avoiding the darker parts of the luminous pattern. ”

“ It is much [19] more likely that the mirror bore on its back a large flower, than that it bore the word meaning a large flower.
Except for obscure references such as these, there is no record of real magic mirrors prior to 1832. Yet a few did undoubtedly exist. There were some in the collection of the royal family of Savoy at Turin, which were later examined by Professor Govi. There was one reputed to be magical in Berlin. The great Von Humboldt thought it worth his while, in 1830, to bring this mirror to Paris to show it to his confrères of the Académie des Sciences ”

“ Researches of Ayrton and Perry, and those of Bertin, of Laurent, and of [25] Muraoka. First, Ayrton and Perry set about procuring mirrors from the shops in Japan, and found that the vendors were in many cases wholly ignorant of the existence of the magic property. Further, the mirror makers could not say how the mirrors became magic, nor which of their mirrors were such; or they gave explanations subsequently found false, declaring the effect to be produced by application of an acid paste to etch the face prior to polishing. ”

“ The mercurial amalgam used in polishing the mirrors consists, according to Dr. Geerts (op. cit.) , of quicksilver, tin, and a little lead. Ayrton gives it as one of tin to one of quicksilver. Champion and Pellet (op. cit.) give the composition as:
[77]
On the occasion of the delivery of this discourse the Author exhibited a collection of thirty-four Japanese mirrors, and by the aid of a lime-light lantern displayed their magic properties upon a translucent screen. ”

“ For example, the curvature of the rectangular mirror, Plate VI., as measured from left to right over the convex surface, is, on the average, about 0·2 dioptries (or its radius of curvature is about 5 metres) , but when measured at points over the vertical bamboo stems, its curvature falls to less than 0·05 dioptrie, and in some parts is absolutely flat, or even slightly concave. ”

“ There is made in high relief, and polished bright so as to stand out from the background, a simple bold symbolic device, sometimes a Chinese character signifying “good-luck,” or “long-life,” sometimes a family crest, such as the imperial kiri (or Paullonia leaves and flowers) , or a circlet, or three feathers crossed, or the jagged peak of Fuji-yama, or the outline of a bird. Ornament of the second kind is in low relief, and, though often symbolic, consists of naturalistic representations of trees, flowers, storks, bamboos, and the like. ”

“ These, when mounted on an air-tight back, could be made to show either positive or negative figures by diminishing or increasing the pressure of the air behind the mirror by means of a simple india-rubber pear attached by a flexible tube to an aperture in the back; the pressure of the hand sufficing to bring out the optical effects. Laurent further showed that by taking an ordinary piece of mirror glass (patent plate glass silvered at the back) magic effects could be produced by lightly pressing against the back hot pieces of metal on which a raised [32] pattern had been engraved. ”

“ Plate II. is taken from a mirror upon [35] which there is, in high relief, polished, a crest consisting of the imperial kiri within a circlet, together with a landscape of storks and bamboos in lower relief. In this case only the ornament in high relief produces any effect: and it is interesting to notice that, whereas the circlet on the back is a simple flat band, the circlet in the image (which is distorted in consequence of a general distortion of the mirror face as a whole) presents double lines. ”

“ One of the latter, in his possession, an old mirror covered at the back with Chinese characters, has no magic qualities at all. The large rectangular mirror is slightly convex, but more so in its longer direction than in its breadth. The bamboos in the pattern, though [37] not very highly raised, are in very sharp relief, the mirror being, apparently, an ichi mai buki, or artist’s proof. There are two raised lumps on the back, apparently the remains of the parts where the metal was poured into the mould ”

“ This being established, they then investigated the process of mirror manufacture, to ascertain how these delicate inequalities of surface arise; and they found it to be due to an accident, or incident, of manufacture. All the finished Japanese mirrors may be observed to be slightly convex in the face. They are cast in moulds, the surface of each half of which is quite flat save for the ornament incised on the mould for the back. The following is Ayrton and Perry’s description of the process of casting. ”

“ Flaws in the face of the casting are filled by inserting little balls of copper—giving rise, perhaps, to the idea that inlaying was used to produce the illusions. The handle is not cast along with the disk of the mirror, but is attached afterwards. ”

“ 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. ”

“ It can also be shown to a few persons at a time by means of the flame of a paraffin lamp twenty feet away, or even by the light of an ordinary candle a couple of feet away. In the case of these weaker sources of light the mirror must be held close to the white screen or card upon which the image is to be received. ”

“ Printed by order of Ye Sette, and issued on May the 4th, 1883.
Edition limited to 250 copies.
2. Codex Chiromantiae.
Appendix A. Dactylomancy, or Finger-ring Magic, Ancient, Mediæval, and Modern. (pp. 34.) Presented on October the 12th, 1883, by Bro. Ed. Heron-Allen.
Edition limited to 133 copies.
3. A President’s Persiflage.
Spoken by His Oddship W. M. Thompson, Fourth President of the Sette of Odd Volumes, at the Freemasons’ Tavern, Great Queen Street, at the Fifty-eighth Meeting of the Sette, on December 7th, 1883. (pp. 15.) ”

“ Presented on November the 5th, 1880, by His Oddship C. W. H. Wyman. 1st Edition limited to 25 copies. (Subsequently enlarged to 50 copies.)
2. Glossographia Anglicana.
By the late J. Trotter Brockett, F.S.A., London and Newcastle, author of “Glossary of North Country Words,” to which is prefixed a Biographical Sketch of the Author by Frederick Bloomer. (pp. 94.) Presented on July the 7th, 1882, by His Oddship Bernard Quaritch. ”

“ George Clulow, President; with a summary of an Address on “Learned Societies and Printing Clubs,” then delivered by Bro. Bernard Quaritch, Librarian. By Bro. W. M. Thompson, Historiographer. Presented to the Sette by His Oddship George Clulow. ”