1833.] Miscellaneous. 215 
I have since examined several varieties of such buttons, and I find that they almost 
all give either radiations or great numbers of narrow concentric rings, (and some- 
times both,) whose centre is the centre of the button, and the smallest one of which 
is always like a dimple in the centre. . 
“Upon examining the surface of these buttons in the sun’s light, and at the edge 
_ of a shadow*, I have invariably been able to see the same rings excavated in the 
polished face that appeared in the luminous image, which it reflected. They obvi- 
ously arise from the button being finished in a turning lathe, and the rings are 
produced by the action of the polishing powder, or probably in some cases they 
may be the grooves of the turning tool, which have not been obliterated by the 
subsequent processesf. 
“ These facts will, I presume, furnish us with the secret of the Chinese mirror. 
Like all other conjurors, the artist has contrived to make the observer deceive him- 
self. The stamped figures on the back are used for this purpose. The spectrum in 
the luminous area is not an image of the figures on the back. The figures are a 
copy of the picture which the artist has drawn on the face of the mirror, and so 
concealed by polishing that it is invisible in ordinary lights, and can be brought out 
only in the sun’s rays. 
“« Let it be required, for example, to produce the dragon described by Mr. Swinton 
as exhibited on one of these Chinese mirrors. When the surface of the mirror is 
ready for polishing, the figure of the dragon may be delineated upon it in extremely 
shallow lines, or it may be eaten out by an acid much diluted, so as to remove the 
smallest possible portion of the metal. 
“The surface must then be highly polished, not upon pitch, like glass and specula, 
because this would polish away the figure, but upon cloth, in the way that lenses 
are sometimes polished. In this way the sunk part of the hollow lines will be as 
highly polished as the rest, and the figure will only be visible in very strong lights, 
by reflecting the sun’s rays from the metallic surface. When the space occupied by 
the figure is covered by lines or by etching, the figure will appear in shade on the 
wall, and vice versa.”’ 
In spite of the overwhelming authority opposed to me, I feel reluctant to give up 
the theory I ventured to advance, in explanation of the anomaly in question, and I 
am emboldened to maintain it by the simple fact, that Sir David had not yet seen the 
mirror: indeed in this respect we stand an equal ground ;—the mirror was gone from 
Calcutta before I had attempted to solve its nature: it had not arrived when Dr. 
Brewster offered his ingenious theory, The best arguments which I can advance in 
favor of my own are—l1, that the mirror underwent several rude processes of polish- 
ing in Calcutta, so much so, that most of its silvered surface was worn off, and yet 
its reflective faculties were unimpaired. 2, no signs of engraving were observed on 
the surface, under the strongest horizontally reflected light, which ought to have 
shewn its presence as explained, by Sir David. 
Dr. Brewster’s theory cannot fail however to win converts: it would be pre- 
sumption in me to go farther in opposing it, than to request a suspension of judg- 
ment until the mirror shall have arrived in England; meanwhile its magical powers 
must continue, as he says, “‘ to perplex the philosophers of our eastern metropolis !’’ 
* “By this method the figure in the Chinese mirror could be rendered visible beneath 
its polish.” 
+ “In polished steel buttons the reflected light is crowded with lines running at right 
angles, indicating the cross strokes by which they have been ground and polished.” 
