Maryland independent. [volume] (Port Tobacco, Md.) 1874-current, 1908-03-13
THE LAMP OF THE FUTURE.


Many attempts have been made to
increase the efficiency Of our present
electric incandescent lamps, says
writer in Casters Magazine.
Light is only a by-product in all
known illuminants. for the production
Of light depends on inoandescence,
that is. the shining Of hot bodies. be-
cause they are hot.
Such hot body radiates a variety
Of waves, but very few Of these are
useful as light The useful light rays
only appear when the temperature is
fairly high; below that only long heat
waves appear. BY increasing the tenn
perature 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
increasing the working temperature
Naturally there must be certain
temperature where the percentage Of
visible radiations reaches the maximum
and this is supposed to be between
1000 and 5000 degrees Centigrade
But even at this temperature the eff
cheney only amounts to about per-
cent, so that there is an absolute linn
1t in lighting by incandescenoe.
The familiar electric inaandescent
lamp consists of a filament Of carbon
enclosed in vacuum. The carbon FL
ament is heated by the electric cur
rent and forms our hot body. Now,
carbon is apparently the most refrac-
tory of all substances. its boiling point
being about $500 Centigrade
Unfortunately we cannot use such a
high temperature in the carbon incan-
descent lamp. for our limit is not the
boiling point but the temperature at
which the evaporation becomes so
great as to limit the life of our lamps.
The temperature at which we work car
bon in our lamps is about 1900 degrees.
The efficiency OF the incandescent
lamp can therefore be increased by
using a material which has a lower
vapor tension at a higher tempera-
ture.
Nernst was the first to devote his
attention to the problem and brought
out the well known Nernst lamp. The
filament consists principally of zir-
coma magnesium oxide and a small
amount of the oxide of the yttria
group.
Great hopes were entertained when
the Nernst lamp appeared on the mar
ket, but these have not been realized,
for the lamp had one great dlsadvan-
tage which has never been overcome
namely, the filament does not conduct
and consequently does not light up
at ordinary temperatures.
The success with these experiments
led scientists to turn their attention
to other rare metals. of which the fol-
lowing have been used with success.
tantalum, tungsten, chromium and
iridium.
The tantalum lamp has so far been
the most successful of all metallic fila
ment lamps and thousands are now
in use in London alone. There is no
doubt that. within very short time
we shall have at our command metal
IN uiulutitt ldilipo Which, llOul d UidJ-
tical point of view will equal the pres
ent carbon lamp and have an efficiency
of 1 watt per candle
This will be a great achievement,
but It will not be the lamp of the fu-
ture. For as shown in the beginning
of this article we are absolutely limit
ed as long as we cling to incandescent
bodies for light production.
Heat. although capable of making a
liquid or solid incandescent, cannot
make gas incandescent. but merely
increases its pressure. We can, how
ever, set gas molecules in vibration by
chemical reaction or electric stress,
such as is done when an electric cur
rent is passed through a vacuum
tube.
theoretically, there is no limit to
the efficiency of a lumineseent gas
Within the last few years good eff
cieneies have been obtained with the
Moore vacuum tube illumination, and
this method Of light production has
great future before it. The light of
the future will be lamp giving light
without heat and the probabilities are
that this will be either a luminescent
gas or vapor.