SCIOPTICON MANUAL.
199
or other object, in the aperture at 0; after which it is
brought to a focus by the object-glasses at F, and finally
again polarized, or analyzed, by the Nicol’s prism F, and
thence thrown on the screen, the disc on which should
not exceed three feet in diameter.
Fiff. 57.
The phenomena connected with the polarization of
light are attended by a most gorgeous display of colors,
and are, in consequence, among the most attractive in
the whole range of physical optics ; an apparatus, there¬
fore, which facilitates their exhibition to an audience
becomes a most valuable adjunct to the magic lantern.
The subject itself is, however, of too recondite a naturo
to admit of adequate treatment in the present manual;
the reader is therefore referred to Pereira’s lectures on
“ Polarized Light,” “ Ganot’s Physics,” and other works
on Physical Optics.
The objects best suited for the polariscopo are designed
with films of selcnito of various thicknesses and forms;