Sunbury American and Shamokin journal. [volume] (Sunbury, Northumberland Co., Pa.) 1840-1848, 1842-02-26
vol. tl--SO. NNTs.
The Sttsa.

mOng many things highly curious, we
find the following observations on the
sun. Whether he principal fact is es.
tablshcd with all the certainty OF ma
thcmatical demonstration, will, perhaps,
be questioned. Those who think with
Euler and Sir John HerschcI, that light
is not a substance. but a vibration, like
sound may not readily admit the theo-
~ OF polarization, or, if admitted, may
have some other explanation of the phe-
nOmouOn. IL.
81 was discoursing, at the conclusion
of the last lecture, on the circumstan-
ces and physical state of the surface OF
the sun.-There are some very striking |
facts connected with this subject, which |
have been bat recently untolded, and OF |
which many are the discoveries Of IL
wing philosophers. It was the opinion !
of Sir William Hershel, (and his sup> !
position had many advocateS,) that the !
sun is an opaque globe entirely cove:
ed by luminous fluid OF some kind, but
whetheril be an ocean OF liquid fire like
motion iron. or an ocean of gaseous
! fluid, as of flame, or yet again, an m
candcscent solid like iron glowing with
! white heat, remained wholly without
| explanation until within a very recent
| period. But the question has now been
reduced to positive, absolute demon
stralon, and the process by which 1t
was done and the circumstances at
tending it, afford beautiful example OF
! the mode in which the different sciences
minister 70 each other.
"ln optics a beam of light is proved
| to be susceptible of u peculiar modlilca-
ton Gated polarization All light Is
proved to lie in either polarized or
unpolarized state. and although it may
not be easy TO explain what is meant by
the polarization of light, still by the aid
of (anciful illustration | can give You
a notion of it sltliclcntI y precise for our
present purpose. Suppose this wand,
which hold in my hand, to represent
raw of light: it has four sides; suppose
the two opposite sides, which are paint
ed blue, to possess certain property,
and the other two opposite, which are
coIorcd red, TO possess property dii-
fercnt from the first. This wand, then.
exactly represents polarlZed ray oi
light. II all the sides had the same
properties, then it would represent All
unpolarized ray. Now, Hight may un-
dergo certain change which shall po-
larIZe---impa.tiDg 10 two OF lis sides,
opposite to each other, a certain pro-
perty which the other two do not pos
sesS. The question arises: What are
these propertis 5? They are various I;
one, however, is so simple and so near
p " connected with the demonstration to
which ] call your attention, that | will
mention it. If ray of light fall upon
rejecting surface with either OF those
two sides which are represented by the
red sides of the wand, it will be reilec-
ted al an angle equal to that by which
it approached the surface. Bot if it
strike the surface upon the opposite sides
the bue-it will not be reflected at
all. so that two OF its faces are capable
of reflection, while the other two are
not. In ray which is not polarized,
reflection takes place under all circum-
stances, but with polarized light, only
under certain conditions. Thus we
5 see that light may exist in two distinct
t states; the one mpoIarized, or It's ordl-
C nary state, and the polan@ed or lis eX-
: traordinary state.
Let us turn to another branch OF
physics. The science OF heat has re-
ceived more attention for few years
\. past than any other branch OF physics.
/, Fourier, French philosopher has done
T. much in this department of knowledge.
q One Of the concluelons he established is
his: There are three states in which
/ material bodies exist, namely, the solld,
: liquid and gaseous. He proved that
=, when a solid body becomes lncandeS>
cent, the iighl It emts is po'arizcd, and
that the light OF incandescrnt gases, as
, flame is unpolarzed. These facts are
, true, whatever may be the nature OF
the materials. Here is "a distinction
established between the light emitted
by incandcscent solids and liquids, and
that emitted by gases, Now Nj. Ara
90 has, with Most beautiful Sagacity, a.
vailed himself Of these two facts, con
tributcd by the scehces of light and
D heat, to determine the nature of the
i suns atmosphere. This may easily be
{ done, for since it is established that the
light from incandesCent solids and Ii
= qulds is polari2ed. and all that need be
s. done 10 determine this point is to Try by
experiment whether lis light be polari'