The Red Cloud chief., 1886-03-12
BULBS AND HORsEsHOEs.


~
Tho tcsAdescent electric light has
become q familiar object to everyone.
The little glass bulbs with their brilliant
horseshoe Of glowing filament attract
no more attention than the Pickering
gas JET. But the fact about the gasjet
are easily and generally understood,
while the lamp Is still . puzzle to many
people. Both produce light by incande-
ceuce. The molecules Of gas are yend-
cred i~ncandcscent by the heat generated
BY the combustion Of other molecules.
The blue portion Of every gas flame is
where combustion is taking place, and
from that comes the heat which keeps
the rest in a state Of incandescence.
With the electric lamp it is the heat pro.
duced by the friction Of an electric cur.
rent compelled to go through a fine car
bon filament, which raises that filament
TO q condition Of incandescence and pro-
duces light.
The three substances which enter into
the composition of an electric lamp are
glass. platinum wire. and bamboo or
paper. Glass bulbs, are readily pre-
pared by the usual methods Of glass
blowing, but the preparation Of the
bamboo is q delicate piece Of work. In
the best lamps the little horseshoe is
made Of bamboo, and this material has
proved its superiority to its rival, paper,
in several WAYS. The bamboo comes
from Japan in bundles Of slips a foot in
length. japanese bamboo is of finer
quality than the Chinese. 1t is first split
up into little square strips. Girls round
these off by running them through dies
until they look like little brown straws.
These are put in cruciblcs with graphite
and submitted to a white heat for sever
al hours. This carbonizes them thor
Oughly. The filaments are not all Of
exactly the same size when taken out of
the crucibles, and if used in that state
would present varying r%esistances to the
current and the lamps would not be
even and economical in their working.
To make them uniform they are put one
by one into a glass jar from which the
air can be exhausted and a h~ydrO-car-
bon gas-the lightest Of the products of
petroleum-can be admitted. A current
of electricity is run through the horse
shoe filament and it absorbs carbon
from the gas until the operator sees that
its resistance has been reduced to the
regulation mount. The standard used
in the factory from which this descrip-
ton was obtained is go Ohms. The
moment when the resistance has
reached the desired point is told by
means Of an apparatus familiar to cleo
tricans-the WheatstOne bridge.
NJ, Al. 1-,r <, - xI-.. ,...,, Al.
bulb, the carbon filamcnt, and the stop
per containing the two platinum wires
which are to connect the horseshoe Of
carbon with the system of wires that
carries the current all over a building
to the hundreds of lamps. 1t only re-
mains to put the stopper in its place at
the larger end of the pear-shaped glass
bulb, seal it alright i'm the flame of q
blow-pipe, extract the air from the bulb
by a mercury pump and then seal the
other end. The bulb is made of the
thinnest glass. and before the air is ex-
hausted from it will break easily. After
the vacuum is created. however, it can be
handled carelessly without injury; and
when it does break there is a report like
that of a dozen pOpguns.
The lamps are expected to burn six
hundred hours. Sometimes, like other
articles of human manufacture, they fall
short of expectations. The competitive
trial recently made at the Franklin in
stitute of the lamps of various compa-
MES furnished several woful examples Of
this truth. A well-made lamp will last
that length of time, however. If by bad
workmanship air is allowed to leak in,
the carbon burns out quickly. If it Is
run ut too high a tensiOn-that is, if too
much current is sen through it, the fric-
ton wears out the little horseshoe in a
shorter time and it breaks. 1t is the
necessity for a practical absolute vacuum
that requires the employment of the pla-
tinum connecting wires. Platinum is
the only metal which expands and con-
tracts with heat at the same rate rs
glass. keeps the joint, where the wires
pass through the glass, always tight SO
that no air can enter. There is a fort.
une in store for the inventor who can
get up some kind of cement that will
prevent the passage of air. and ut the
same time admit the Use of cheap cop
per instead Of costly platinum wires.
The problem may be capable of solution,
for this whole matter of electric lighting
is still in its infancy, though not a most
vigorous stage of infancy.-NeW York
Tribune.