28 Professor Aijrton [Jan. 24, 



Verona, who was afterwards condemned to death by Martin della 

 Scala, as well as of the one discovered in the house of Colla da Rienzi, 

 and on the back of which was the word " Fiorone." Bnt of these 

 magic mirrors which have played so important a part, not only in 

 the priestcraft of China, but also in the oracles of the Greeks and 

 Etruscans, and in the witchcraft of the middle ages, inquiry has shown 

 that Japanese literature makes absolutely no mention. 



Is it, then, that such mirrors cannot be found in Japan? Un- 

 doubtedly they cannot be bought by inquiry at the shops, but Pro- 

 fessor Ayrton's investigations have shown that if a careful examination 

 with properly arranged light be made of a large number of the 

 ordinary Japanese bronze mirrors, a few, perhaj)s two or three per 

 cent., will be found showing the phenomenon clearly. 



The lecturer then referred to the extracts he had made from a 

 large portion of all that had been written in various languages regard- 

 ing the explanation of the phenomenon. He mentioned that the 

 earliest explanation was given by a Chinaman, Ou-tseu-hing, who 

 lived between 1260 and 1341, and who also had the impression that 

 the magic property of the mirror was produced by an artifice ; for he 

 wrote : " 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 orna- 

 ments 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 co]3per 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." 



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 jiaper communicated some years ago to the French Academy of 

 Sciences, the well-known French writer on China, M. Stanislas Julien, 

 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 mirrois. Even in the country itself 



* 'J'his ])roljal)ly refers to the mercury amalgam ^Yllicll is used in polishing, 

 and wJdch Ou-tseu-hing mistook for lead or tin. 



