The bronze looking-glasses of Japan have the curious property of showing
in their reflection of a strong light on a screen, not only their own
polished surface, but the figures on the back.
These figures are fashioned by striking them out; they are then ground
down till the raised metal is levelled to the deepest indentation, when
the pattern is stamped once more, the face again ground, and the
operation repeated.
The alteration in the metal where this compression has visited it, is
not perceptible even with a magnifying glass, but in reflection it is
shown.