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108 - Scientific Intelligence. 
eated in the figure; A, being t 
Nicol’s prism, and CD the polar- 
izing mirror, 
It is a brass box 81 millim. 
HEGF is the dichroscope which is placed in a polariscope as ind 
the ? 
closed by opaque slides, or by 
plates of colored glass; a single (ae 
glass plate, or sets of glass plates, can also be inserted ia the direction — 
, as seen in the figure. The side HE, is destined to receive cool 
glasses, crystals, or a rotating cireular-polarizing plate of mica, The side 
ean be closed by a slide having in it a slit for prismatic analysis or 
a circular aperture for experiments, with fine gratings. ‘Iwo mirrors be 
long to the apparatus: one is silvered, the other blackened. 
being assumed that the linear analyzing arrangement is so placed 
that in a crystal of cale spar cut at right angles to its axis and pla 
between A and IIE, the rings and black eross are visible, the following 
combinations may be obtained. 
_ 1st. Employing CD the silvered mirror and EF the glass plate: ordinary 
light reaches the analyzing prism from CD and linear polarized light 
from EF. 
{a.) FG closed by an opaque slide: white linear-polarized light. Re 
(6.) FG closed by the slide, in HF a colored glass: according to the 
on of the glass, monoghromatic or polychromatic linear-polarized 
ight. Pie 
(c.) Colored glass at FG, HF open: unpolarized colored light and white 
linear-polarized light. The cross is seen brightly colored in the tint of the 
ror. 
mica plate at HE is used, circularly or elliptically polarized, reach the 
Nicol’s prism, 
They are (a), both white or both colored, (4) white and colored, {c) dif 
ferently colored, according to the arrangements made. : 
. Between the mirror CD and the plate of glass EF, the mica plate i5_ 
inserted: in this manner combinations of cireularly or elliptically polarized 
light, with linear polarized light are obtained. , 
At silvered mirror is placed at CD and a set of six glass plates 8 
inserted at EF. This is so arranged that the light entering from CD and 
polarized by refraction in passing through EF is equal in intensity to the 
light polarized by reflexion at EF: the two beams are of course polarized 
