The sun., 1872-12-23

in a solar microscope. and an Image of the Aim
the Illuminating beam adds Itself To that already
impaired tu the glass plate, 80 that after n mo
s @ or T2 1no MN ma"% Sa@ ho eS Sss IN VIM
moeculc, aud you have most impressive dis
play of cr,stallziiR energy ovcrsprcadng the
similar II you lreathc upon the frost-ferts
which ovelspread your window-panes ia winter,
And then ohscryc through a lens the subsequent |
recorrc tuition ut the ilu.
licre the ciy tillim. force is hsmpered by |
the adhesion Of the Elm to che glass ncvcrthe- |
lhL rLAY OF POWER IL sTRIKINGLY BEAUTIFUL
Sometimes the crystals start from the edge uf |
the crystalZation being once started, the mole |
cuIcs throw themselves hy preference on the
prcriplt lion upon itself which IS not pos
Sc scd 10y the solid glass. Sometimes the |
CRYSTALS start from definite nuclei In the
centre of the Gm; every small CRYSTALLINE
PARTICLE which rests in the film furnishes start
ng point. Throughout the process YOU notice
one feature winch Is perfectly unaterahle and
! frori trunk, and from these branches others
shoot hut the angles enclosed by the splCulr
are uualtcrable. In like manner you may ind
/ tails distorted In shape. They are thus far at
but In one particular they assert their supcriutl-
! ~ over all such accidents angular MAGNITUDE
/ is always rigidly preserved.
TIM stcoNp EXAMPLE.
! Nv second example Of the action Of crystal
| liaiug force II thus ~ sending Noitaic current
through the liquid. you know that wc Geyon-
! pose tile lipu,i and Il II contains a metal, We
ihcratc this metal 10y the elccirolysis. lhis
small cell contains as luton OF su'ar 81 ieai,
| and this substance is chosen hec1use lead lends
itself So freely TO this crystazlnR power Into
| the cell dtp tw1 very thin piatinhm wfes' nnu
| voltaic battery. ON sending the voltalc current
| through the sului ON the lead viii be slowly
! severed from the atoms with which IL f. now
| combined; IT viii he liberated upon one 81
the wires, and at the moment Of It's liberation it
win obey the polar forces of IT, atoms, and pro-
|
| They are now before you, spruuting like ferns
from the wire, appearing indeed like yegetHbe
growth rendered So rapid a. to be plainly visible
to the naked eve. ON reversing the current the=c
wonderful lead .fronds will dissolve, while from
the other wire nlaments OF lead dart through
the liquid. In n moment or two the growth az
the lead trees recomnences, hut they now cover
the other wire. In the process OF cry stallzat on
Nature first reveals herself as a builder Whore
do her operations stopl Does she continue by
the play of the same forces to form the vcgeta-
BILE, and afterward the aniuIsl1 Whatever the
answer 20 those questions may be, trust me that
this mystCgiou thing which we call matter, will
be very different from those OF tile generations
There Is hardly more beautiful and instruc-
tive example of this play OF molecular force than
seen the cxdusiic frond like forms produced 10y
the capitalization uf a
FILM OF WATER oN COLD WINDOW PANE.
You have also probably noticed the beautiful
rcsettcs tied together 10y the Crystall1ing fore
during the descent OF n snow shower on a very
calm day. The slopes and submits Of the Alps
frost. They vary Infinitely in detail OF beauty,
but the same angular magnitude Is preserved
| throughout. An innexible power binds spears
and splculp To the angle of sixty degrees. The
| common ice of our lakes IS also ruled IN its de-
| position 10y the same angle. You may sometimes
see In freezing water small crystals of stellar
shapes, each star consisting of -iI rays with tbs
angle Of sixty degrees between every two of
them. This structure may he revealed IN ordin-
airy e. In sunbeam, or failing that, in our
enough TO unlock the frozen molecules without
disturbing the order of their architecture.
Of Hight In water and gla% e greater than In air
according to the undulAt ory theory, the rcyerso
Is the case: This point has been subjected TO
the test of
Az EXPERIMENT rRorosHp ny ARAGo,
and executed hy Foucanit and Filenn, and de-
claed ia favor u the undulatoTy theory. Whon-
| ever the two theories have come Into collision
this has been the result.
Consider small portion of wave issuing
| from point OF light so distant that the portion
may he reg arded as practically straight Moving
vertically downward aud npnring on a hori-
through the glass without change OF direction.
But a. the velocity in glass Is less than The
passing into tie ienser medium.
Hut suppose the wave, before reaching the
glass, to he ohlisue 20 the surface that end 81
the wave which Grst reaches the glass win he
the frst retarded. the other portions ~ they
enter the Euss being retarded In sue essipu.
This rctardaiiou Of the one end Of the w.Ne
causes It to swing round and change u front,
giss- - course - ohidue ~ its or,g,npl drec-
ton. Aceor..nT N the uhdGiatory theory light
The double rcfrsctlon ~ Iceland spar was nrst
, trcltod iu wurA published hy Erasmus BAR
thuhmAs, In lCji
TIIE CELEBRATED HuYGnENs
sought to account for the phenomenon on the
prn piles Of Ne wave IhsSTy' aud he riecreded @
N cong so. ne inaa, ,i, aghy linpSrttHt t "h,er
! heans transmitted by tie spar; Newton, re-
hectng "a the observations Of HuyEhens' came
two -des and from { he analogy OF this two
sidedne-s with the two-end -dness of magnet,
"a rail ~ FfHNIaW Ia TI.N
cspe /" Ss dessibca as fSisrl1sj. wv '''''''
lhe quality Of two-sidedness n.erTed upon
light hy Iceland spar may hc conferred upon IL
, hy ordinary reflection, Malus made this discoy-
/ efy in iSIs while cooking through Iceland spar
at the iight OF the sun rejected from the win
, dows VI the Luxembourg palace in Paris, ! re-
ceiye .pon plato OF window glass the beam
4 iected S from the glass Is pcarized; the vibra-
tions OF this beam are executed for the most
part parallel to the surface of the glass, and IL
; hold The glass 50 that the beam shall make nm
! angle oi hityeight degrees with the perpsndicu-
lar to the glass, the whole of the reflected beam
, is poarzed. II was at this angie that the image
ofthe tourmaline completely quenched In
our former experiments. 1t Is called the polar
: rIIr EXPERIMENT OF NAILS.
. And now let US try 20 make substantially he
! experiment Of MIius. l receive the beam from
the lamp upon this plate Of glass and reflect II
= through the spar. Instead of two Images, ol
see hut one. SO that the light, when polar1ed
, | ~ 1t now is, can only get through the spar In
one direction, and consequently produce but
/, | a. In the touruaine, all the vibrations of lie
ordlnar, light Hre reduced to two planes AT ri slt
angles to each other; but, unlike the tOurna-
line, both beams are transmitted with equal
| facility IS the spar The two beams, in short,
I cucrsent from ihe spar, are polaT2ed. thtir
! directions Of vibration being al right angles TO
! each other. when, therefore, the ilght was
polariZeC 10y reflection, the direction u vii ra-
lion Ia The spar which corrCspUndcd 10 the d.
recti0n Of Vibration Of the poiari1ed beam trans
mittcd u, AID that direction only. But one
I 7 IMAGE, therefore, was possible under the 0ondi-
tons,
And now you have 1t In your power TO
! CHICK MASY or MY STATEMENTS,
! and you will observe that such logic as connects
, our experiments Is simply transcript Of the
4 ! logic of Nature, On the screen before you trs
. | the two disks OF liglt produced b. the double
refraotion Of the spar They arc, As you know,
A | two imuges Of the aperture through which the
| light issues from the camera Placing the tour
! maine IN front Of the aperture, two images OF
| the crystal Will be obtained; but now let us
4 | reason out what ls to be expected from tn =
! ! experiment The light emergent from
! tie tourmaline Is polarized. Placing the
, ! crystal with Its aka horizontal, the
| vibrations ot transmitted light will be
horizontal Now the spar has two peFpendiqu-
lar directions Of vibration, one OF which at the
present moment Is vertical, the other horizontal
/. | What are We to conclude2 Why, that the green
s lght will be transmitted along tho latter, wh ICh