The Hickman courier. [volume] (Hickman, Ky.) 1859-current, 1879-02-07
japanese Magic Mirrors.

At q 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 1S77-7S, had led
him to believe that there existed ex-
.remely slight irregularities in the eurv-
ature of the polished surface (quif, in
visible to direct vision) of such a nature
that the thicker parts, corresponding OF
course with the raised patte-f.ss-shs
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
convergent and divergent beams OF hight.
which the authors have availed them
selves of, and the use of which constitu-
ted, he said, the esseues of the system ot
investigation EN- .,Ioyed by Prof Perry
and himself, and he explained hat il
this theory of the phenomenon was cor
rect, then placing the screen, on which
the reflection OF the light from the
japanese mirror was cast in a certain
position, the phenomenon ought to dis
f appear and again putting the screen in
, another position, the phenomenon ought
J TO be inverted that Is, instead Of bright
image on 3 dark GROUND, which hitherto
had alone been what has been Observed
by previous investigators, dark image
T of the pattern on a fright ground ought
to appear, This disappearance and abs
solute inversion of the phenomenon he
] said he 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.
e Various other facts, such as theneeessity
/ of holding the screen rather lear, but
e not very near, the mirror whenordiDary
= sunlight without lenses was employed
was, like the inversion phenomenon just
referred to, shown to be explaiuablt
only on the inequality of curvature
theory, and rot on the inequality OF den
) sity theory,
The next question that arosewas, how
: was this inequality of curvature pro.
s duced? This was explained 10 be due
to the method employed by the Japaues
for making the face of the mirroy convex
o which method had hitherto f8quite
= unknown to foreigners, but whh Prof
Ayrton had, after much trouble, iounc
d to cossist in scratching the face Will,
) cold with megebo, or distorting rod.
During the operation the mirror became
i visibly concave, but, receiving buck
le," they sprung back again so IS to be
Il come convex when the pressure of the
7 rod was removed. The thicker parts o
these magic mirrors yielded les undel
G the pressure, were made less oDncavt
Il when under the rod, and sprung bacl
less, or became less convex when the
pressure of the rod had been removed
then showed how this explained tht
fact discovered by Prof. Atkinson, of th,
r Imperial University, japan, in 1877
= that a small scratch made on the back o
= mirror with blunt NALL although
/ producing apparently no effect on tht
Q other side, became nevertheless visible a
d bright line on the screen whens ligh
Q was reflected on the mirror.