There is
such a lens fitted up in the shops, with the title of _optical pillar
machine_, or _diagonal mirror_, and the print to be viewed is laid upon
a table beyond the stand of the lens, and its reflection in a mirror
supported diagonally over it, is viewed through the lens. The illusion
is rendered more complete in such a case by having a box to receive the
painting on its bottom, and where the lens and mirror, fixed in a
smaller box above, are made to slide up and down in their place to allow
of readily adjusting the focal distance. This box used in a reverse way
becomes a perfect camera obscura. The common show-stalls seen in the
streets are boxes made somewhat on this principle, but without the
mirror; and although the drawings or prints in them are generally very
coarse, they are not uninteresting. To children whose eyes are not yet
very critical, some of these show boxes afford an exceeding great
treat."
_Cosmoramas and Dioramas._
"A still more perfect contrivance of the same kind has been exhibited
for some time in London and Paris under the title of _Cosmorama_ (from
Greek words signifying _views_ of the _world_, because of the great
variety of views.) Pictures of moderate size are placed beyond what have
the appearance of common windows, but of which the panes are really
large convex lenses fitted to correct the errors of appearance which the
nearness of the pictures would else produce.
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