Year: 1873

Jupiters pc3ns. He converter them into so many
shadow Of the planet ana reehed when they emerged
from the shadow They enabled him to prove that light
the astounding velocity cf ooc miles second. Then
came the English astronomer Bradley who noticed that
described in the heavens every little orbit resem
bling the eaTths orbit The result perpexed hn; out
Bradley had mind open TO suggestion, and capable or
seeing, I'm the smallest fact picture Of the largest He
was one day upon the Thames in boat, ana noticed
that as long as his course renamed uhehanged tne
vane upon his masthead showed the WIND 70 be
blowing constantly In the same direction, but
change in the direction OF his boat. Here" Whe
well was the image OF his case The boat was the
a star" You wall Immediately understand the meaning
OF Bradley's discovery Imagine yourself IN motion
tically downward. The moment the train begins 10
the raindrops begin TO slant and the quicker the
train the greater the ooquity. In precisely similar
manner the rays from !. star vertically overhead are
caused to slant by the motion Of the earth through space
falling drops, tho velocity Of the drops may be calcu
ated and knowing the speed OF the earth In her orbit
and the obliquty OF the due TO this course can
calculate just as easily the velocity Of hight. Bradley
did this and the alteration Of light hls discovery is
called enabled him 10 assign TO II a velocity almost iden
teal withthat deduced by ROemer from totally differ
ent method OF observation.


SCIENCE PARALYzED By THEORY.


Up to his demonstration Of the composition OF white
light, Newton had been everywhere triumphant
triumphant In the heavens triumphant the earth, and
his subsequent experimental work for the most part
Of immortal value. But infahbility IS not the gilt oil
and after his discovery Of the nature OF white


light Nevton proved himself human. He supposed that
refraeton and dispersion went hand in hand and that
you could not abolish the without at the same time
aboshng the other. He maintained this opinion TO the
end Of his lfe and thus retarded the progress OF sbse
combining together two different kinds of glass, you
might abolish the color and still leave residue of
refractiOn; and he applied this residue 20 The the
no color which Newton Thought an impos-
sibility But Newton committed graver error than
this. Science, as sought 10 mako clear 10 you In our
The roots Of phenomena are imbedded region beyond
the reach of the Senses and less than the root OF the
matter will never satisfy the scientific mind. We find
accordingly in this career OF optics the greatest minds
constantly yearung TO pass from the phenomena TO their
causes-to explore them 10 their hidden roots. They
thus entered the region of theory, and here Newton
drawn st more strongly toward the error and made it
his substantial choice. His experiments are mpersh-
dam across the of discovery; but like all barriers
upon authority and not upon truth the pres
barrier away. This, you know, was done mainly
through the abors OF Thomas Young and hs lustrious


In 1908 Maus looking through Iceland spar at the
reflected from the window OF the Luxembourg Pal
in Paris discovered the polarization or Hght by
reelection. In 1911 Arago discovered the splendid chro
matte phenomena which we nave had III illustrated oy
The rotdon 0f the plano OF p0alLaoD Dy quartzcrys.
tails In 1913 seebeck discovered the OF ght


os magnificent bands of coors that surround the axes
II Lnxia. crystals In 1914 Woaston discovered the


ng Of Iceland SPAR All these effects which, without


eG st clue We uld leave the mnd in q hopeless Jungle
o.. pnenomena without harmony relation, organ
connected by the theory OF unduation The theory


appued and verified in all directions AIRY being espe-


y conspicuous for the severity and concusveness OF
his proofs The remarkable veIication fell ~ the
lot of the late Sir William Hamilton OF Dublin, a pro-
found mathematician who, taking up the theory where
Fresne had left arrived at the conclusion that at four
special points at the surface OF the ether-waye IN
d0ublerefcng crystals the ray was divided not into
two parts into infinite number OF parts; forming
these points continuous oonical envelope instead OF
when Sir william Hamilton inferred its existence.
Turning to his irend Dr. Lloyd ne asked him TO test
Lloyd, taking crystal OF arTagonlte, and following
with the most sCrupnous etaotne5s tne ln9uatoIs oi
theory cutting the crystal where theory said II ought 10
cut observing 1t where theory said II ought 10 be
previously beeu mere idea in the mind OF the mathe-
matcnn.


INHERENT STRENGTH OF THE THEORY OF UsDULArIoS.


But while have thus endeavored in these lectures TO
illustrate before you the of tho unduatory theory
as solver OF all the difficulties of OPTICS do therefore


wish you to close your eyes against any evidence that
may arise against it BY no means; we leave it to
others to shrink from the contemplation OF truth be-
cause it may be for tho moment disagreeable. You
may urge, and justly urge that hundred yosr5 ago
another theory was held by the most eminent men,
and that as the theory then held had TO yield, the
undulatory theory may have yield also This is per-
fccty logical but let US understand the precise value
OF the argument In similar language person in the


time OF Newton even in our time, might reason thus
"Hipparchus and Ptolemy, and numbers Of great men
them believed that the earth was the center OF the



have 10 give way also" This is just logical the
first argument Wherein consists the strength OF the
theory OF gravtaOn7 Solely in ts competence TO
for all the phenomena OF the solar system. Wherein
In It's competence disenange and explain phenomena


hundred fold more complex than those OF the solar sys
tenn Be skeptcal, II You like, regarding the undua
tory theory if your skepticism be philosophical, 1t will
wrap the theory of gravaon In the same great doubt
many another truth which in the Ongrun has proved
blessing humanity. had to establish by hot conflict
it, II had been ennncated by Hooke, it had been APP
Piled by Huyghens, it had been defended by Euler But
they made impression. And, indeed, the theory In
their hands was analogy than demonstration.
1t first took the form OF demonstrated verify IN the
hf ads of Thomas Young He brought the waves OF
light 90 bear upon each other causing them TO support
each other and TO eXtingulsh eaeh other at Will From
applied bis determinations in all directions he showed
that tie standing difficulty OF polarization might be en-
braced BY the theory


FREsNEL's ACHIEVEMENTS.


After him came Fresne whose transcendent mathe-
matcal abilities euabed him TO give the theory gene
ralty unattaned by Young He grasped the theory in
its entirety; followed the ether into its eddies and esu
aries in the hearts Of crystals Of the most complicated
structure, and into bodies subjected to strains and
pressures. He showed that the facts discovered by
Malus, Arago, Brewster, and Bort were many gan.
ga SO to speak, Of his theoretc organism deriving from
II sustenance and explanation. With mind too strong
for the body with which it was associated, that body
became wreck long before it had become old and Fres
mel died, leaving behind him name immortal IN the
annals OF science.


One word more should like TO say regar ding Fresue
There things ladies and gentlemen better than
There matters of the character we'll as
matters of the intellect and 1t is always joy TO those
who wish TO think well OF human nature when high in
elect and upright character combined They were,


believe, combined in this young Frenchman ln those
conflicts othe undulatory theory he stood forth
a of integrity claiming no more than his right, and
ready concede their rights to others. He at once
recognized and acknowledged the merits OF Thomas
Young Indeed, 1t was he and his iellowcountry-
man, AragO, who first startled England into
the consciousness of the injustice done 10 Young
in The Edinburgh Repiep 1 should like to
read you brief extract from letter written by Fresnel
Young in 1924 as it throws pleasant light upon the
character Of the French philosopher. For long time,
says Freshe that seDsbility that vanity, which
people cal love Of glory has been much banted in me-