The prison mirror. [volume] (Stillwater, Minn.) 1887-1894, 1891-12-03
Points About the Electric Lamp.

Points About the Electric Lamp.
Many hundred pounds of platinum, worth
about as much as gold, are lost every year
in worn out incandescent electric lamps.
Millions of these bulbs are produced yearly.
and are used up in from 600 to !, 900 hours
each. Most of them, when the life of the
lamp is exhausted, are much as they were
when the lamp was first sent out from the
factory. The little loop of carbon. which
is the soul of the cOntrivance, is broken
and useless. but the bulb often remains in
tact, and the two little threads OF platinum
that convey the current to the vacuum
within are as good as though they had never
been used One of the many hopeful and
ingenious men occupied day and night in
solving electric problems, has found prof.
table way of saving this platinum. 1t
sounds like small matter but it will be
worth many thousands of dollars yearly.
A fortune awaits the man that shall in
vent method of saving the bulbs them
selves. or cOntrive bulb that shall be as
nearly as may be true vacuum, and yet
admit of replacing worn out carbon loop.
The present bulb is the nearest approach to
a vacuum known to science. The little
button or point at the end of the bulb
marks the place at which the vacuum was
sealed. That is the thickest part of the
bulb. Other parts are rarely more than
1-32 of an inch in thickness. but they bear
with ease the atmospheric pressure Of fit-
teen pounds to the square inch to which
they are constantly subjected. Now ,and
then. however, they cOllapse-or explode"
according to the erroneous popular notion
apparently without cause. For the most
part the collapse comes because of some
change in the internal conditions. Every
bulb is known to contain slight trace of
highly rarefed air. If there were much of
it the carbon loop would instantly be con.
sumed when the current was turned on.
AS it is, the carbon does undergo some com.
bustion. 1t one of the bulbs contains lit
tie more air than another. and If the carbon
be slightly defective. there may be little
more than the usual amount of combustion.
The trace of oxygen present in the highly
rarefed air joins with the carbon to form
carbonic acid gas; this produces slight
change in the internal conditions. and if the
bulb has weak point the atmospheric
pressure from without cruShes in its frail
sides. The dim and smoky look of some
long used incandescent lamps is due to this
combustion of carbon. InfinteSimal pOr-
tiOns of the burning carbon fall upon the
inner surface of the bulb and are welded to
the glass. 1t is generally believed that
perfectly spherical lamp best endures the
constant air pressure to which it is SUBJ
jected; but the common pear shaped lamp
has been adopted partly because of its
beauty, partly because it is more easily and
less expensively made. and partly because
1t will hold longer loop of carbon than the
corresponding sphere.
On all lamps sent out from the factory is
marked the candle power. This is for the
information of the consumer. There is
another mark on the lamp less conspicuous
and not especially addressed to the con-
sumer. This mark is found on the white
plaster covering the upper end of the bulb.
It indicates the number of volts that will
produce the registered candle power. The
ordinary 16-candle power lamp is marked
from 116 to 1913 volts. The average is per-
haps 100 volts. The lamp may be run at a
much higher voltage and with higher result
ant candle power. but the carbon will not
long endure the strain. 1t is burning the
candle at both ends. so to speak. The cleo
trio light stations are provided with an
ingenious device for guarding against such
a strain. Should some accident happen
whereby large part of the lamps run by
one current was cut off in body, the ef-
feet would be to subject the others to a
higher voltage than they were designed to
stand When such an accident happens
the pressure indicator at the station comes
into play. This is device for measuring
the voltage of current. Just above and
attached to the instrument is an incan-
descent lamp run by the current that the
pressure indicator measures. When an &C
cident happens this lamp suddenly intensi-
fies its glow. This serves to call attention
to the fact of something unusual, and indi-
Gates higher voltage than the system Of
lamps is designed to endure. At the same
time the gauge of the pressure indicator
marks the number of volts. The attendant
instantly regulates the dynamo until the in.
dicator registers the proper number of volts.
IN. Y. Sun.