National Republican. (Washington City (D.C.)) 1872-1888, 1874-12-18
POLARLZRD LIGHT.

DIR. E. @. BOLLES' SECOND LECTURE.
Lincoln hall was handsomely filled last night
by an audience intent upon the instruction az
forded by Dr.. E. O. BOlles' lectures.
THE LECTURE.
DR.. Bellies as Introductory to his experiments,
said that with all the improvements of the mi
croscope there were some things 1t could not
show, such as the arrangement Of matter in the
molecule structure Of crystals, organic bodies and
transparent bodies under tension. No amount Of
magnifying power would reveal these things, but
they may be brought to view by the employment
Of light In the condition In which 1t Is said to be
polariZed.
When ordinary light is reflected from glass ct
an angle Of about hityfour degrees Il is split into
two parts, each Of which is IN different eondi-
tion from the original beam. The same change
may be impressed upon light by passing through
certain crystals, called dOublY refractinR ones or
by dispersion by small particles, and in some In
stances by the ordinary refraction Of transparent
bodies. Light thus changed is called polariEed
light. 40 49,. -,
to differ from common light. To show itsquality
1t must be passed through the same or an equiva-
lent apparatus as VIII be required to polarlze 1t
at first. This apparatus is called the analyIer,
while its partner Is the polarEer. In the expert
ments Of this evening q bundle Of plates Of glass
is the polariEer, while the anslyzer is a doubly
refractory crystal Of calcareous or Iceland spar.
The Doctor proceeded to illustrate the use Of this
apparatus, and passed on to explain the peeu-
liarity Of polarized light It was neither re-
beam Of polarized light was entirely stopped by
3 clear, transparent crystal, leaving the screen
dark.
The polarization Of light was IN fact the reduc-
tion Of all the light vibrations in beam to SIM
gle plane and the optical structure Of crystalline
bodies was shown to bear q peculiar relation to
the extinction Of vibrations in single plane.
These vibrations might again have their plane
changed by the introduction into the interrupted
beam of substances like crystals, many organized
bodies, Sc and the peculiar lines and eolors pro-
duced under such circumstances were the founda-
ton of pOlnrIscope analysis.
Commencing from this point, DR.. Bolles illus
trated the application Of these principles to sscer
tanning the Intimate structure Of various objects.
Experiments with crystallian Aims Of quartz,
mica and selenite were shown and the variation
OF color explained in its relation to the thickness
Of these Aims. Beautiful designs, In themselves
colorless, were shown magnihed and glowing
with brilliant eOlors upon the screen. Blocks Of
glass, whose Interior portions were in state Of
tension, were shown to reveal this fact in highly
eolored fringes, curves and circles The tnytsi-
Bile structure Of horn, tendOns and hbres was
also exhibited in its colorless pictures, and the
live larVa of a gnat was introduced TO show the
wonderful flashes Of light produced by the polar
izipg action of fits muscles. Capitalization was
also exhibited under the microscope and with
polorized light, and the lecture was concluded
with demonstration Of the gorgeous colJrs OF
large number Of chemical substances and salts.