The Bolivar bulletin. [volume] (Bolivar, Hardeman County, Tenn.) 1865-1888, 1879-02-06
Japanese Magic Mirrors.

At a recent meeting of the London |
Royal Society, Prof. Ayrton gave an ex-
PLANTATION of the sO-called magic property
possessed by certain rare bronze mirrors,
sold by the Chinese at about twenty
times the cost of the ordinary mir ors
OF that country, and which consisted in
these mirrors being able to reflect from
their smooth, polished faces the raised
patterns Of birds, flowers, dragons or
Chinese letters, with which their backs
were adorned. His experiments, made
during the winter OF 1877-78, had led
him to believe that there existed ex-
tremely slight irregularities in the cuTv-
ature of the polished surface quite in
visible to direct vision) Of such 2 nature
that the thicker parts, corresponding of
course with the raised patterns on the
back, were fatter than the remaining
convex surface, so that there was less
dispersion Of light from the thicker por-
| ton than the thinner. He described
one Of series OF diagrams illustrating
various experimental arrangements Of
convergeut and divergent beams of light,
which the authors have availed them
selves of, and the use of which constitu-
ted, he said, the essence of the system Of
investigation EN- yloyed by Prof Perry
and himself, and he explained that if
this theory of the phenomenon was cor
rect, then placing the screen, on which
the reflection OF the light from the
Jop3nese mirror was cast in a certain
position, the phenomenon ought to dis
appear and again putting the screen in
another position, the phenomenon ought
to be inverted; that Is, instead of bright
image on a dark ground, which hitherto
had alone been what has been observed
by previous investigators, dark image
OF the pattern @n fright ground ought
10 appear. This disappearance and sbo
solute inversion o. the phenomenon he
said be had found to actually take place,
but that he was compelled, from want
Of time, to leave the experimental ex-
hibition of it for the Royal institution.
, Various other facts, such as the necessity
OF holding the sc. cen rather near, but
} not very near, the mirror when ordinary
sunlight without lenses was employed
was, ike the inversion phenomenon just
referred to, shown to be explaiuablt
only on the inequality of curvature
theory, and not on the inequality OF den
sity theory,
The next question that arose was, how
was this inequality of curvature pro
duced? This was explained to be du,
to the method employed by The Japanes
for making the face of the mirrors convex
which method had hitherto been quit
unknown to foreigners, but which Prof
Ayrton had, after much trouble, founC
to consist in scratching the face Whit
cold with megebo, or " distorting rod.
r During the operation the mirror becam
visibly concave, but, receiving a buck
Ie," they sprung back again so as to be
! come convex when the pressure Of IL
rod was removed. The thicker parts 0
these magic mirrors yielded less unde
the pressure, were made less concav
i when under the rod, and sprung bac
n less, or became less convex when III
pressure of the rod had been removed
then showed how this explained tn
fact discovered by Prof. Atkinson, OF til
r Imperial University, Japan, in 1877
- that q small scratch made on the back c
Y mirror with q blunt nail, althoug
/ producing apparently no effect on tn
G other side, became nevertheless visible 8
d bright line on the. screen when a Iigh
q was ref cted on the mirror.