SCIENCE. 



417 



in relief of more or less perfect workmanship. Japanese 

 mirrors usually are more beautiful than the Chinese. 



Here, gentlemen, are a few. I cannot pass them 

 among you, but I can show them to you perfectly well 

 by means of the magic lantern. This one is the copy of 

 a mirror brought from Japan by Professor Dybowski. 

 This second one belongs to General Teissier. The de- 

 signs are of the reverse or unpolished side. 



Among these mirrors there are a few of a lesser thick- 

 ness, which possess a remarkable property. Although 

 they reflect ordinary images in a diffused light, if a ray 

 of sunlight falls across the polished surface and is re- 

 flected upon a white screen, the ornamentation upon the 

 reverse side will be transported to the screen. This is 

 what we call a magic mirror. 



The first that appeared in Europe came from China. 

 The Chinese, in fact, have known of them for a very long 

 time. One of their historians who flourished in the 

 eleventh century of our era, mentions them with admira- 

 tion. Another writer, who lived in the year 1300, gave 

 us a supposed explanation of the phenomenon. The 

 Chinese Encyclopedia contains an article upon the sub- 

 ject, which has been translated by our great sinologue, 

 Stanislas Julien. These mirrors have always been rare, 

 but persons who have lived in China assure me that they 

 can sometimes be found in Chinese curiosity shops. 



We are not sure that the mirrors were ever purposely 

 made. It is probable, on the contrary, that they are 

 merely the result of imperfect fabrication. In regard to 

 the Japanese this is absolutely certain, for magic mirrors 

 are unknown in Japan. Neither the manufacturer nor 

 the person who sells them has any idea of their peculiar 

 property. European savants, however, have found 

 magic mirrors from Japan many times. In 1832 M. 

 Prinsep described one in the Journal de la Societe 

 Asiaiique, which he had discovered in Calcutta. In 

 1877 Mr. Atkinson, Professor in the Imperial University 

 of Jeddo, observed that numbers of Japanese mirrors 

 produced magical effects. This attracted the attention 

 of M. Ayrton, Professor in the Engineering School in the 

 same city, who immediately began to investigate the 

 matter. After examining five or six hundred he affirmed 

 that three or four out of every hundred were magic. 



Partially magic mirrors ought to be very common, and 

 I am quite sure if I had been permitted to examine the 

 Japanese collections in Paris, I should have found several. 

 I am indebted to General Teissier for two beautiful mir- 

 rors that he brought from Japan. One of them is de- 

 cidedlv magic. I will have an electric light thrown 

 across it and then upon the screen. You will see a part 

 of the design upon the back appear. 



Although we can furnish no written testimony con- 

 cerning these mirrors, several learned men however, es- 

 pecially those who had traveled extensively, knew all 

 about them. In the year 1830 Humboldt came all the 

 wav from Berlin to Paris, in order to show the Academy 

 of Sciences a mirror which he believed to be magic. The 

 experiments were made at the Observatory. Unfortun- 

 ately there are no traces of them to be found in the 

 scientific reviews of the period, but we know that the 

 whole affair was a fiasco. Our illustrious chemist, M. 

 Dumas, who was one of the investigators, affirms that 

 Humboldt's mirror could not be considered magic in any 

 sense of the word. 



The first magic mirror that appeared in Europe was 

 owned by M. Monchez, the Director of the Observatory 

 in Paris. On his return from China he brought with him 

 several mirrors, one of which was magic and had been 

 sold as such. This mirror was presented to the Academy 

 of Sciences on the 22d of Julv, 1844. 



In 1847 a second one appeared belonging to the collec- 

 tion of the Marquis de la Grange. Stanislas Julien gave 

 a detailed description of this one, in which he stated that 

 the reflection obtained was identical with the reverse of 

 the mirror, but that the latter was not in relief. This 



mirror, therefore, should not have been magic at all, or if 

 it was, all our modern theory would be upset. Many 

 attempts have been made to find this mirror, but up to 

 the present time the search has proved fruitless. 



A third magic mirror was presented to the Academy 

 in 1847 by Person, Professor of Physics in Besancon. 

 Person's report consists of twenty-five lines only, but it 

 is extremely important, as it contains the whole theory 

 of magic mirrors, which, until then was unknown. 



Finally, in 1853, Maillard presented the Academy 

 with a fourth mirror, which was not magic to any great 

 extent. It is now in the College de France. I have held 

 it in my hands, examined it carefully, and I can assure 

 you that it is an exceedingly bad specimen. A great 

 deal of imagination must be possessed by any person 

 who can call the effects of this mirror magic. 



This, gentlemen, was the last, and the excitement about 

 magic mirrors began gradually to subside. Nothing 

 more was heard of them till the year 1878, when MM. 

 Ayrton and Perry, both professors in the Engineering 

 School, at Jeddo, presented the Royal Society of London 

 with several magic mirrors which they had brought from 

 Japan. For the first time, technical observations were 

 made concerning the construction of these mirrors. As 

 to the mirrors themselves, the effects produced by them 

 were truly marvellous. We were unable, however, to 

 form any correct judgment upon them until last year, 

 when M. Ayrton brought four to Paris. The experi- 

 ments made by him proved very successful, and were wit- 

 nessed by me with great interest. 



Since then, the fame of magic mirrors has revived with 

 double intensity, 



A few days after M. Ayrton's seance I received a 

 visit from my old pupil M. Dybowski, Fellow of the 

 Academy of Physical Science, who returned from Japan 

 after a professorship of more than two years at the Uni- 

 versity of Jeddo. Of course, you all know that after the 

 revolution of 1869, Mikado's government founded large 

 scientific schools in the capital. Unfortunately, they no 

 longer " import " professors from Europe, but content 

 themselves with such pupils as we turn out. 



Like all Japanese, M. Dybowski was ignorant of the 

 existence of magic miirors. He brought with him, how- 

 ever, as curiosities, four mirrors of antique manufacture, 

 which are called Temple mirrors in Japan, and consid- 

 ered to be superior to modern ones, as the fabrication 

 has grown exceedingly defective of late, owing, probablv, 

 to the competition of European mirrors. We experi- 

 mented together with these four specimens, one of which 

 was found to be magic in a slight degree. This mirror 

 has been the starting-point of all our subsequent pro- 

 gress. Of course, this was naturally the consequence of 

 a sound theory, which, however, was not immediately 

 established. 



The oldest on record is that given by a Chinese author 

 of the thirteenth century. According to him, " the cause 

 of the phenomenon is due to the use of fine and coarse 

 copper. If, in manufacturing the mirror, the image of a 

 dragon is produced in relief upon the reverse, a similar 

 dragon is engraved upon the polished side. This last is 

 concealed by filling up the lines of the engraving with 

 copper. The metal is then incorporated with a purer 

 quality of copper, while the mirror is submitted to the 

 action of fire. Finally, the surface is polished and 

 washed over with amalgam." The author, however, 

 does not seem to see that if the difference in the reflec- 

 tive power of the two qualities of copper was sensible 

 enough to make the phenomenon appear, this variation 

 must necessarily disappear under the application of the 

 amalgam. 



Brewster's theory does not differ notably from the 

 Chinese explanation. He says the polishing effaces the 

 engraving and renders it invisible in a diffused light, 

 leaving upon the metal, however, variations of density 

 and reflective power, which makes the image quite visible 



