1832.] Note on the Magic Mirrors of Japan. 243 



thin coating of silver to give it a white colour. The back of 

 the mirror is deeply carved or indented with ornamental work in cir- 

 cles and festoons, and it bears an inscription in the Japanese character in 

 high relief upon what may be termed the tympanum of the disc : in the 

 centre there is a projecting knob perforated laterally to receive a string 

 for suspending the mirror : the metal is highly sonorous when struck 

 as a bell, and is so soft as easily to be indented or scratched on con- 

 tact with any hard substance. I found its composition to be 



Copper . . 80 



Tin 20 



100 

 with no traces of silver or arsenic, and a very slight indication of zinc. 

 When a strong ray of light, as from the sun, is reflected from the po- 

 lished surface of the mirror upon a screen, instead of a clear bright disc, 

 as would naturally be expected, the spectrum is found to exhibit a to- 

 lerably clear delineation of the ornamental pattern on the back of the 

 mirror: the outer circles; the festooned ring ; the magical inscription, 

 are all seen depicted with fidelity ; and it certainly does stagger an ob- 

 server for the first time to witness an image shadowed forth, without any 

 visible origin ; for the back of the mirror may be covered or concealed 

 in any way without diminishing the effect. 



No irregularity of surface was perceptible on the face of the mirror. 

 It had been scratched in one or two places, and I put it into the hands of 

 a silversmith to berepolished : in effecting this he rubbed off the plating 

 in several places, and exposed the surface of the bell-metal : this, although 

 in some respects a blemish, was one step in a negative investigation of 

 the cause of the phenomenon, for the reflected image continued just as 

 marked as before, merely being of a red colour where the silvering was 

 removed ; thus showing that the cause was unconnected with the nature 

 of the reflecting surface. 



As it was seen that the thick parts, the rim, the festoon, and the let- 

 ters, were those which appeared most illuminated in the spectrum, 

 an obvious explanation occurred, that the light was more per- 

 fectly reflected from thick surfaces than from thin ones, however such 

 an assertion might militate against the known laws of metallic reflection, 

 which all experiments have proved to be purely superficial or confined to 

 an infinitely small depth below the surface : this hypothesis was easily 

 put to the test of experiment, by casting some specula of very unequal 

 thickness, and then grinding and polishing the upper surface : but when 

 the mirrors were thus made ? the image reflected from them was found to 



