National Republican. (Washington City (D.C.)) 1872-1888, 1875-01-06
Figure /.

ACTUAL SIZE OF THE WAVES.
Ls, ne then. see if we can reach any conclusion
as to the actual size Of these waves; me ioIbiS
OF our time, and the extent OF the suDJect, loLOIG
that should here describe the actual metho1
used in any detail, but this BRIEF statement nust
snf5ce ms Very thin films, as you know, produce
eoiorE: witness the sOap-bubble, or this specimen
of Thin scales from ancient corroded glass klndly
sent me by Professor MFign 81 80 mounted IS to
show on the screen with the Oxy-hydrogen IAN
tern brilliant colOrs, were here exhpitedl a..
these colOrs result from simple relation between
the length of the color-Waves and the thlckness
of the tlms, and thus the films become iooLrules
Sor ms measuring The waves. We find By this means
that red wave is about ia COO Of an inch long
green wave about 10000, and violet wave
These numbers. however, convey no idea be-
yond one Of exceeding minuteness, and think
We can get little nearer 10 true conception OF
would say that, as an inch is 10 mile, SO Is
green light wave TO an inch; or, the wave Is as
much smaller than an inch as an inch is smaller
But. again. Mr. Webb, in England, makes,
nv means OF a machine, very ine writing on glass.
This writing is so fine that it becomes a TEST
for the power Of a microscope. Thanks 10 the
skill Of Dr. J. J. W Woodward, director oil the army
Medical Museum, by whom the photograph was
made and TO Mr.. John CBrbut, Of the Photo
Relief Company Of Philadelphia, by whom the
glass picture was prepared can es IN tSe
screen. II contains, as you see, the L9rd
PRAYER in a running hand. To form some idea OF
this result of simple calculation. II the entire
Bible we're written in the same manner l. would
be contained pa ana New sss innb T st NJ
see If we can establish any relation between t1ls
writing and the size Of light waves. On the
same glass picture with tie Webb test are a Sc
Ties OF ruled bands, photographed, also by Dr.
Woodward with the same lens from plates ike
wise intended tests for microscopes, and known
from their maker NobeTt's bands. Inc nrst
Of these whose lines are about equal 10 those OF
the Webb test, has these lines liz goo Of an men
aIart. or would afford space for three red waves
beIBeen each pair Of lines The fifth band, how
ever has its lines l-36, goo Of inch apart, and
ave But these bands are made much finer
than this. the finest yet resolved being the nine
teentb of the same series, and having l2oOOo
lines to the inch, considerably more than three
times finer than red waves DR.. Woodward has
been go kind TO send me one OF his photographs
made from this object. and have thus the pleas
ure OF showing you the picture Of something pro-
duced by human skill far exceeding in hneness
that almost ipcOnceVably minute thing, wave
such. then, are light waves as regards their
magnitude in leDgth-ObJects almost beyond the
measurable and even capable Of beng exceeded
in minuteness by human ingenuity.
1NCoNCEIvABLR RAPIDITY OF THE WAVES.
Asregards their rapidity of recurrence, how
ever, our maginatiOn and powers of conception
are left helplessly in the rear OF the astounding
These tiny waves, OF which, as we have seen,
5OOO TO 6OOOO may be arranged behind each
other in the distance oil an lncD, run, or ny, or
rather fash forward at the rate of about 200, 900
miles in a second. Two hundred thousand miles
Of them, therefore, enter the eye, or pass any one
miles contains % COO 10 900 OF these waves. The
number Of waves that arrive or pass in a second
is thus for an average ray about 500 millions Of
This number, however, conveys no idea, and ]
hardly hope to aid you by any reduction, but lei
If we counted five a second which is about n.
fast as one can count, and counted day and night
without ceasing, it would take US Just three mil
liens OF years to count the number Of wave!
which enter the eye in one second:
Yet, when you look at colored objects, the reti
ma Of your eye takes cORniZance IN some mysteri
Gus way Of these rapid motions, and dscrimi
mates between the faster and slower rates. II II
does not always count quite accurately, and
sometimes, unoeT unusual conditions, gets con
fused and makes mistakes are you surprised2
TIE ISFIEITE VARIETY IN COLOR.
IICoIor, as we have stated, being synonymou
with wave length, or with frequency of sueces
sion, we easily see that the variety in color Il
practically infinite, involving, as it does. ever!
Numerical interval between forty five millions 0
millions and ninety millions Of millions, at th
least, and, indeed, having no limit which we cal
assign TO its subdivision.
To discriminate between these varieties the eyl
is evidently inadequate, as we shall see NOR
fully further OIL; but let us here pause for a mo
ment TO see what means Of discrimination does lii
in our power.
THE PRISM AND ITS USES.
The most widely useful at present is that fu-
upon this each wave is bent according TO il
length. The shorter the wave the greater is III
bending, and thus, on leaving the prism, eac
length Of wave goes it's own way TO its own place
From the electric light within this lantern Il
Eues beam Of light which, falling on the screer
produces a circle Of tinted light; but when as nov
Il is caused to psss through prism. you see O
the screen not one but many circles Of light, eac
differently cOloTed.
The reason Of this is that, as before said, tn
prism sends each WaVelength in different direC
ton, and thus unrsVels the mingled strand int
the separate threads Of color whose cross section
you now see OF the screen.
There was here shown on the screen. first
sfngIe circle Of pinkish- looking light, and then
when the came beam was passed through tn
prism, there appeared a row Of beautifuIly-eolore
disks-red, yellow, green, blue and yioIet-Whicl
were the separate coloTs at first united 10 III
single disk or circle.
By the use Of the prism, then, or as we saw D.
priEmatic or spectrum analysis we are enabled s
supplement the capacities OF the eye and obtain
when necessary, q most accurate discriminatioI
between waves Of different lengths, or difieren
eOlOTg.
THE EYE.
Such, then, being the psture Of color in ligh.