214 Miscellaneous. [AprIL, 
*“‘ The white semi-transparent glaze is thus prepared. The whitest petuntse with 
green spots is pulverized and washed over ; to 100 parts of the cream thus obtained 
is added one part of che-Xao (burnt alum) previously pulverized. A caustic ley is 
also prepared into which che-kao is stirred, and the cream thus produced is collect- 
ed. The two creams are mixed together in the proportion of ten measures of the 
former to one of the latter, and this composition, washed over the dry unbaked 
ware, gives it its whiteness and lustre. A brown glaze is made of common yellow 
clay added to the above. The Chinese porcelain is never brought to the state of 
biscuit, by a prior baking, before it is glazed. 
“The flux used with colours laid on the glaze is made of one part calcined 
quartz and two parts ceruse. Red is given by peroxide of iron, and a finer red 
by copper, but the process is not known. The enamel colours are brought to a . 
proper consistence by a solution of glue, except those containing ceruse, which can 
only be tempered with water*.”’ ; 
3.—Phenomenon of the Japanese Mirror. 
The Philosophical Magazine of Dec. 1832 contains Sir D. Brewster’s explana- 
tion of the magical effect of the mirror, of which a notice was published by myself 
in vol. 1. p. 242. 
Sir David had only received a written description from Mr. G. Swinton, and 
therefore it was hardly fair to expect him to give a categorical reply to that gen- 
tleman’s question, ‘‘ how are these strange effects produced?’’ After alluding 
however to Mr. Swinton’s conjecture that the phenomena may originate in a differ- 
ence of density in different parts of the metal, occasioned by the stamping of the 
figures on the back, which, if metals were absolutely opaque, and if the lights they 
reflect never entered their substance, would, he says, be the only possible way in 
which the stamped figures could be reflected,—the learned Doctor proceeds to offer 
his own theory. 
“‘T believe, however, on the authority of the phenomena of elliptical polarization, 
that in silver nearly one-half of the reflectedlight has entered the metal, and in 
other metals a less portion. So that we may consider the surface of every metal 
as transparent to a certain depth, a fact which is also proved by the transparency 
of gold and silver leaf. Now this thin film having its parts of variable density, in 
consequence of the stamping of the figure, might reproduce the figure by reflection. 
It is well known that silver polished by hammering acts differently upon light from 
silver that has received a specular polish; and I have elsewheret expressed the 
opinion that a parabolic reflector of silvered copper, polished by hammering, will 
from the difference of density of different parts of the reflecting film, produce at 
the distance of many miles a perceptible scattering of the reflected rays, similar 
to what takes place in a transparent fluid or solid, or gaseous medium. I am 
satisfied, however, that at the distance of a few inches from the Chinese mirror, 
this evanescent effect will be altogether imperceptible, and that we must seek for 
another cause of the phenomenon under consideration. 
“‘ Some years ago I had occasion to observe the light of the sun reflected upon paper 
from a new and highly polished gilt button, and I made a drawing at the time of the 
figure, which appeared in the spectrum. It consisted of radiations exactly like the 
spokes of a carriage wheel,the radiations being sixteen in number, and a little con- 
fused in the centre opposite the eye of the button. On the back of this button several 
words were deeply stamped, but these words did not appear in the reflected image. 
* Trans. Soc. Arts and Repository of Inventions. - + Ed. Trans. vol. xi. p. 47. 
