The herald. [microfilm reel] (Los Angeles [Calif.]) 1893-1900, 1895-11-06
ELECTRICAL NOTES

The following com parison. duo to
Palaz, will be useful to electrical engin-
GERS in presenting the advantages Of cleo
trio lighting from the standpoint of cool
given quantity of light: Arc light, A;
fncandescsnt light IA; kerosene. argand
burner, 3Sl; gas, argand burner, 3so;
candle. 473: gas, butterfly burner, 51l.
The heat question is very important
one, but it 10 as nothing compared with
th's respect. OF course, electricity COM
pares still more favorably with oil other
sources of artificial light.
In paper read before the Royal society
on 1.-THE effect of pressure OF the. sur
rounding gas on the temperature OF the
crater Of an electric arc light" Mr.. w. e.
Wilson states that of late years IL has
often been assn med that the temperature
Of the crater forming the positive pole Of
the electric arc is that of boiling carbon.
The most modern determinations give
that point as abou: 1900 degrees to $500
derses g. In order to investigate whether
increased pressure in the gas surround
ing an electric arc would raise the tenn
psrature of the crater, he used strong
cast-iron box, in the interior OF which
an electric arc light could be maintained.
By increasing the pressure of the gas In
the box the temperature OF the crater is
considerably lowered instead of being
raised, and the experiments seem to
show that the temperature OF the crater
like that of ilament in an incandsscent
lamp, depends on how much it Is cooled
by the surrounding atmosphere and not
on its being the temperature at which
the vapor OF carbon has the same pressure
as tho surrounding atmosphere. That
cabron volatizes in some form at compar-
atively low temperatures seems likely
from the way in which the carbon of in
candesosnt lamp filaments Is transferred
to the glass. The pressure OF the vapor
of carbon in the arc may consequently be
very small, and further it would seem
that the exposition of high pressures in
the solar photssphere is not borne out
by these experiments, and that carbon
may exist there in the solid form at very
high temperatures, although the pres
sures are com parativley low.
In two pole dynamos Inc proportions
of ring armatures vary from length
equal to one.half the diameter to
length equal to one and one-half diam
equal to the diameter. For drum arma-
lures the length Sometimes equals one
and one-half diameters and sometimes
three diameters. 1t is common to find
the length equal to two diameters.
GuttA percha heated in hot water at
about 100 degrees F. becomes plastic, and
will take line impression with slight
pressure. Wnen gulta pcrcnh 10 sVaAeu
for few hours in bsnzole or naphtha, it
becomes swollen. and if it IS then dipped
in hot water 1t becomes so plastic that
1t may be used with safety on very
fragile and delicate objects. Specially
adapted to elect.otyping.
The cotton thread used for the fila
ments of incandescent lamps is parch-
mentized before carbonization by passing
1t slowly through a solution OF sulphuric
acid two parts, water ono part, and
finally washing it in water until every
particle Of the acid is removed. The
rarch msntized thread. after drying, is
reduced to uniform diameter by draw
ing 1t through dies, after the manner Of
wire drawing.
A thermopile. for experimental pur-
poses. may be made Of pieces OF German
silver and copper wire, twisted and
hard-soldered at the ends. forming series
OF pairs. and arranging the wires thus
Joined in many-pointed star, 80 that
the German silver ana copper wires alter
nate. the ends Of the series being left I'M
connected. The INNER points of the star
are heated over q kerosene lamp. The
wires may be No. 16 and six inches long.