The evening star and Newark advertiser. [volume] (Newark, N.J.) 1907-1908, 1907-09-17
THE LAMP OF THE FUTURE.
1t will Give Light Without Heat-The
Fuel Probably a Gas or vapor.

Many attempts have been made 10 In
crease the efficiency OF our present eiectric
lamps. Light Is only a oy-
product in all known iiluminnnt, for the
production of light depends on incandes-
cence-that is, the shining Of hot bodies
because they are hot.
Such a hot body radiates a variety OF
waves, but very few OF these are useful as
light, says Casters Magazine. The useful
light rays only appear when the tempera-
ture Is fairly high: below that only long
heat waves appear. BY increasing the
temperature the percentage of useful light
rays increases.
As long as we only know the way to
produce electric light by incandescence we
can only increase the efficiency by increas-
ing the working temperature.
Naturally, there must be a certain tenn
perature where the percentage OF visible
radiations reaches the maximum, and this
is imposed to be between 1000 and 1900
degrees Centlgrade. But even at this tenn
perature the efficiency only amounts to
about S per cent, so that there is an alb
solute limit in lighting by incandescence
The familiar electric incandescent lamp
consists of a hlament of carbon enclosed in
a vacuum. The carbon hlament Is heated
by the electric current and forms our hot
body. Now. carbon Is apparently the most
refractory Of all substances, Its boiling
D0In1 being ABOUT o.hlU DEGREES Atnllb idhNs
Unfortunately. we cannot use such a
high temperature In the carbon mean
descent lamp. for our limit is not the
boiling point, u the tempsraaurs s a,
as TO limit the life of our lamps. The
temperature at which we work carbon IN
our lamps is about 800 degrees. -
The efficiency of the incandescent lamp
can, therefore, be increased by using a
material which has a lower vapor tension
at a higher temperature.
Nr-sg 1uaa rhn Awaf 70 AaUnfa hiu QtIpn-
ton to the problem. and brought out the
well known Nernst lamp. the nlamenl
consists principally of ~zirconia magnesium
Divide and a small amount of the oxide OF
the yttria group.
Great hopes were entertained when the
Nernst lamp appeared on the market, out
these have not been realized. for the lamp
had one great disadvantage which has
never been overcome. namely, the hlament
does not conduct, and, consequently doei
not light up at ordinary temperatures.
THE success with these experiments lee
scientists to turn their attention to Other
rare metals. of which the following have
been used with success: Tantalum, tung
stem. chromium and iridium.
The tautalum lamp has so tar been tht
most successful of all metallic hlameDi
lamps. and thousands are now IN use !,
within a very short time we shall nave al
our command metallic hlament lamp:
which from a practical point of view, vii
equnl the present carbon lamp ana nave al
efficiency of one watt per candle.
This will be q great achievement, but II
will not be the lamp of the future. For as
shown in the beginning OF this article, w
are absolutely limited so long as We cllng
10 incandescent bodies for light produc'
tlon.
Heat. aIthoush caoahle Of making a liq-
uid. or solid. lncandescent. cannot make {
gas incandescent. but merely increases Its
pressure. We can. however. set gas mole
culcs In vibration by chemical reaction ol
electric stress. such as Is lone when al
electric current is passed through a vac
uum tube.
Theoretically. there is no limit TO the II,
hcfcncy OF a ~luminescent gas. Within the
last few years good ef~lciencies have beer
obtained with the Moor vacuum tube illu.
mlnation- and this method OF light prcduc'
lights Of the future will be a lamp givinl
light without heat. and the probabilities
are that this will be either a luminescen
gas or Nnpor