New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1872-12-20

the visible spectrum are those Of the extreme violet the
longest those OF the red while the other colors
are OF intermediate pitch waye-length The Length oI
a OF the extreme rcd is such That II would ghi
e Qs OF them placed end end TO cover one men, We
ca 63 of the extreme violet would be required 10
VI" te Veocitv of light IN round numbers 10000
miles per second. Reducing this To inches, and multiply
ing the number thus found by 36gs, we obtain the nun
her of waves OF the extreme red In 10000 miles All
these waves enter the eyo and hit the retna Mt the Daek
of the eye in one secOnd. Inc nuiOer Oh bnocHsP ~
second necessary to the production of the OF
red is therefore four hundred and hfty-one millions
OF millions. In a similar manner, IL may DC io. .h
impression Of violet is seven hundred and eighty,
nine millions of millions. All space Is nn ter
with matter oscillatng at such rates From eyery st ~
waves Of these dimensions move with the VeiocSS %
light like spherical shells outward ANA IN tne o. tbe
just in the waer-indeed more truly tuan m ann ru
water-he motion OF every particle Is the I S
Of all the separate motions 70 e S occur
at point, 1t Is made good at some otner oti
atty as if it alone had its thrills through space
The principle OF interference applies to the waves 0,
sound And the conditions of interference are the same
IN all three. II two series OF hghWaVes staI. az
| same moment from a common origin, crest concues
with crest sinus with sinus and the two systems olen
together TO a single system OF double anphouuIb,
hnfh series start az the moment, one OF them now
| ever being at starting, whole waVeTenRth IN au-
vance of the other they also add themselves T3sesne
and we have an augmented luminous effect Inc SAINT
occurs when one system Of waves is any number OF
whole waveengths in advance OF the other But .ae
one system half waveength, or any oud hunoel Vi
half waveenghs in advance then the cTests vi V &
TEN a upon tne sSds sc M he partce: of ether at the
naces where the other tends depress them
hence through ther lons at' T tber ia what we call
darkness which corresponds, as already staleu Will
dead level In the case OF wafer
CONDITIONS FOR THE GENESIS OF COLOR
It was stated first lecture. with reference to the
colors OF absorption that the formation Of natural bodies
is seecve creative that what they dd was 10 PICK
out certain constituents Of the white solar nght ior eA
tncon this causing them to appear In the coors Oh tne
unextinguished light 1t must at once Hash upon your
| haVe
agency by which light may be sefextngulsDed' we nave
in it the conditions for the production OF coo but
the question faces u.s. How Is IL that certain constituents
are quenehed by interference, we Others are pere
remani This entirely que TO the difference Id 'n'
| lengths OF the waves of light.
The subject is most easily illustrated by the class OF
phenomena which first suggested the undula0ry theory
| 10 the mind Of Hooke These are the colOrs OF thih
films OF all kinds which are known TO men OF science
as the coors thin plates In this relation no Object
i'm The world possesses deeper scientific interest than
a common soap-bubbe. And here let me say emerges
one of the difficulties which the student OF pure science
eneouners i'm the presence Of practical communities
like those OF America and England II Is not 10 De eA'
pected that such communities entertain any pro-
| found sympathy with labors which seem FAR removed
from the domain Of practice. Imagine Dr. Draper
inc their colors! Would you show him the necessary
patience grant him the necessary supports And yet
be it remembered thus that Newton spent large
portion OF his time; and that 1t was on such e1Perl
ments that has been founded theory the issues OF
Whence, then, are derived the colors OF the soap
bubble Imagine beam OF white hght lmp9gi ha ge En
bubble When IL reaches the first surface OF the MN
| a known fraction Of the light Il rejected Dack buI
|
second surface and is again IN part rescteui Ill, me
from the second surface thus turn bac. ana o
| pursue the from the first surface And II the
thickness of the film be such as to cause the necessary
retardatlon, systems OF waves interfere Win
ouadrupling it, totally extngushing IT, as the case
may But inasmuch the waves OF hight are OF ar
ferent gths il plain that TO produce selfextnc-
the Of the longer waves greater hckness
Of film necessary than IN the case Of nS snole 05
are not quenched the production OF color IN the
| case of thin plates.
| SUBTLE THEORY USRAvELED
The governmental illustrations be introduced In the
lecture are the coors Of oil upon water the colors Of
film Of air uclosed between two glass plates the colors
Of films Of oxide used a guide in the tempering OF
| polished seel the coors OF the soap-bubbe by trans
mission and reflection finally, the celebrated expert
| ment by which Newton determined the thickness OF
soapbubbe from its color and known as the experiment
Greatest dhculiy that Newton ever encountered He
quite n1 @ no ss n & AT tie
very outset his theory confronted by the question:
Why, when beam OF light is incident on
transmitted Is 1t that there are two KINDS OF par
oles the specially fitted for transmission and the
other for rehectoni This cannot be the reasoh5 1or
| If allow beam OF light which has been rejected
general rule is also divided into reflected and trans
mitted portion. Thus the particles once reflected are
% sTI away Newton saw ali t6 he
| knew he had TO explain why II Is that the seltsame
moment transmitted. 1t could only be through some
change in the condition Of the particle itself The self
| same particle he affirmed Affected by hts or
| easy transmission and reflection.
IThe experiment of a thin film upon the surface OF
wuer was accomplished by pouring spirits OF turpentine
through pipette upon water in tray illuminated by
| the electric light. The colors were distinct, but
an accidental excess OF trpentne thickened the film
| 80 az TO quickly obliterate them. The soap
bubble colors the finest Prof Tyndall said he had
ever succeeded in getting at any lecture. When reflect
| ed light was thrown through the bubble the whole
screen covered with the most coors call
ing forth loud expressions OF delight from the audence
| II you are willing TO follow while l unravel this
theory of fits. most subtle, perhaps, that
tered the human mind think the intellectual discipline
will repay you for the necessary effort OF attention
Newton was chary OF stating what he considered 10 be
the cause fits but there cannot be doubt that
his mind rested mechanical cause. Nor there
be doubt that as IN all attempts theorizing he
compelled TO fall back experience for the materials
his theory. His course OF observation and OF Thought
| may have been this From magnet he obtained the
notion of attracted and repelled poles What more nat
ura than that he should endow his ghtpartlcles with
such poles Turning their attracted poles toward
transparent substance the particles would be sucked In
would be driven away reflected Thus, by the ascrp-
ton poles transmission and reflection OF the self
particle at different times might be accounted Tor
| MENTIONS MARVELLOUS ExACTITUDE.
| At the point which have now attained, Newton's
ingenuity in preserving theoretic conception entire
reached its climax. Regard these rings Of Newton as
seen pure red light they alternately bright and
dark The film of air corresponding the outermost
Of these rings is not thicker than ordinary soap
bubble, and II becomes thinner on approaching the
center; stu Newton. e l have said, attempted to
difference OF thickness between ring and ring. How
he did this may be thus made plain TO you. Suppose
would then accurately represent the earhs curved
face. Let perfectly horizontal plane touch the surface
at any point. Knowing the earth's diameter, any
gneer or mathematician IN this room could tell you how
at ten yards at 100 yards at 1000 yards distance from
the point OF contact OF the plane and the It's
for the curvature Of the earth Sewtons cal
culaton was precisely similar. His plane glass was