A peculiar kind of porcelain was formerly manufactured in China,
which exhibited its colour and devices only when filled with water.
Though the art of manufacturing this porcelain has been lost, and the
mode cannot now be described with accuracy, the following has been
conjectured as not very remote from the truth. The first requisite was
that the vessel be extremely thin, so that the figures to be formed
might be sufficiently clear and perceptible. After the vessel has
been baked, the figures, which were mostly fish, (as those were most
appropriate with the water), were formed on the inside; and, after the
colour had dried, a second extremely thin coat, of the same substance
as that of which the vessel was constructed, was lain on the inside
and varnished. The fish, or other device, would then, it is evident,
be enclosed between the two coats of the ware of which the vessel was
made. All that remained to be done was to grind the outside of the
vessel as close to the figures as possible, to varnish it again, and
bake it a second time; and though, after this operation, the figures
and embellishments would not be at all perceptible, yet, so soon as
the vessel was filled with water, they would at once be rendered clear
and distinct to a degree scarcely credible. Attempts have been made to
revive this beautiful art, but hitherto without success.