, 1879-02-20
THE ELECTRIC LIGHT.
A Clear Exposition by Prof. Tyn-
dali.
How the Electric Current Is Changed into
Light by Resistance.
The Professors Iden Of Edison'a At.
j.. tempted Invention.

Bistance. Flowing through perfcct conductor,
no matter what tho strength OF the current
might be, neither heat nor light could bc dcycl-
opcd. A rod Of 1snreststing copper carries away
rninlurcd and unwarncl m atmospheric dis
charge competent to shtvcr to spltntcrs a resist"
ing oak. send the telf.sane currcnt through
wtrc compostd Of alternate lengths of silver
and platinum. Tho silver offers little rcslst-
anee, tho pintfnum Offers much. Tho cot,se1
queucc Is tlfat tile platinum Is ralscd to white
heat, while The silver is not ylsihly warmed.
The eame holds good with regard to tho carbon
terminals employed Tor the production OF the
electric light, The Interval between them offers
apowcrful resistance to the passage OF The cur
rent, and It Is By the gathering tip Of tho force
necessary to burst across this iuteruni that tho
voltaic current Is nbln to throw the carbon Into
that stnto Of vo!cut intestine cotnmolon which
we call heat, and to which its effuigc.ee Ia due.
The smallest interval of mir usually Butlicas to
stop tho current. But when the carbon points
nrc frst brought togtlier and then separated,
there occirs between them a discharge Of In
cantlceccnt matter which carries, or may carry.
tho current over n considerable space. The
light comes almost wholly from the iucandezcent
ca1bons. Thr space between them Ia tlElc.l with
a blue flame which, bClnE usunlly btnt bV tho
carh's magnetism, rcrciyca the rarnc OF the
Foltnlc Are.
hFor seventy years, tlien, VIC have bcca in
possctk1ol, OF this trahscchuens nght "nhoiit
Applying IT to the illumination uf Our streets
md houses. Such applications suggested thctn-
selves At the 0utsft. but there wcsc Ernsc utt-
nculties iu their way. The first difficulty arose
1tom the waste OF tile earbnue, wtsh arc ds-
part BY the electric transfer Of ,Hatter from
The one carbon to tlie ofllcr. 70 keep tho cur
nous a. the proper distance as'lsr % regulators
s wsTe tS cyse s sa5 t. svs y snIs'
and serr!il, wpo nafe nechshrcgcaea ny 4ioln,es'
slenens, bruwnng, CARR, ttrn!ntne' Lontih.
Mini otheTs' by s"ca asfsnNeanents inu hlht
difficulty was practically overcome; bns tse
Eeco'ld, Il EraTcr onc, y pronaoy inseparab!e
IRON Inc CONSTITUTION OIL Lnc SolLAle uattcf5' IL
a''ses 'ro'n -
TUE otsHAlioS of THAI ,sE1o1"n1.h !, Ia"
which throughout the material universe de-
andS ta an eye 'or CPS an ese ~ a's4 i,, aoo'n @ LOT
TOOTH, refusing 10 yIeid tIie iaiHteat GlnW OIL
neat or R'nnef o. Ilght w1tiont tlc expenditure
" M absolute equal qnantMg ot sonio
other power. Honcc. IN practice. ahe Acsir,
upon the value Of tlc pro;luet ,., "a
relation to that Of tht power efpenart!. TIC
inctal enc ean DC 3nEnt itHe pansr IL fnlgnt pe
ignatci IN 'lnne, ht y Is possible Il. avou Inc
Introduction oi ai forrlgls neat alla 70 bofn tle
x,nc @ tn air "l tne tcMpeTatafo ol tMs rnonl
This Ii done by placing zine toll Ut the focus Of
eonsase mirror, Wnleh eohgenttaes 70 ai.,t
violet llainc, ai!'t We COULD reaniiy aeferini!le
tlie An'ount Of heat generated bv its conhus- %
tson. g.lt ztnc can 90 burnt not only IN nlr nllt
IN LIQUIDS ltis tfns :. o4sns + WI wnen @ aeit!,llnted
wafer is rnured over It; II Is also thus lr,lt ~
the Violate oattcry. Here, However, to obtain
the oxygen necessary lor its combustion. lhe
enc has to aisodso the nSufpGeh VIII whlst
,.ne oxygen y eom5!ncu. Tue consequence
ia thAt thc ilcat anc 10 thH eonnus-
ton OF thc metal in tho liquid Tolls
short Of Tint doycopsd bY iis eombus-