Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1890-12-14

pole of the dynamo and the other to tine
other pole of the dynamo as shown and Indl-
Gated in the figure by the wires and signs,
plus and minus.
Between 'j'' and sc" there is represented
q solinoid or coil of wire; inside the solenoid
there is loose iron core, which is attached
to the lower carbon. The solinoid is con-
nected to the circuit on either side of the
| two carbons, as shown at &c" and 81" II
now there is an electric current generated at
Cd, " the current will start from ''a" and
60 to 'c;" at SC" the current will divide,
| part going through the solenoid 81 e" to
''f" and so back to "b." The other part
| will pass to the upper carbon "g, then
| jump to the lower carbon "h," and so to
If" and then back TO ''b."
TOWARD THE LEAST PRESSURE.
However, at ''c'' the current will divide
itself according to the resistances of the two
| paths. In other words, the strength of the
currents in the divided parts of circuit are
inversely as their resistances. The action
| in the arc lamp is then as follows: When
the current is started, the cir
| cult through "g" and Ssh" will
pass through the solenoid 81 e." The
action of the solenoid will tEen be to draw
the carbon "h" up against the carbon ''g."
! Under these circumstances the greater
| portion of the current will pass through the
| carbons, but now the soenoid will lose
much of its power and the carbon oh" will,
by the force of gravity, fall away little
I from the carbon "g," and an electric arc
| will be formed between the two carbons.
The falling away of "h" increases the re.
sistance OF the circuit through "g b" and
the solenoid will again be energized, but this
time not so much as before. The carbon
/ "h'' will thus yibrats back and forth few
times till a state of equilibrium is es-
| tablished between the force of gravity and
the force Of the solenoid. When this is
done the carbon "h" will maintain its posi-
tion quietly SO long as the air space between
"g" ard 'h" is kept constant.
coMPENsATEs FOR THE BURNING.
This space, however, does not remain con-
slant. 1t increases as the carbons slowly
burn away. Now, this increasing of air
space between the carbons means an increas-
ing resistance in the circuit "g h." and
any increase in the resistance OF the circuit
"g h'' will cause more current to flow
through the circuit 81 e." and this increase
of current in the circuit j e" means an in
crease in the power Of the solenoid. The
core of the solenoid will thus be drawn up
higher and push the carbon "h'' up toward
the carbon "g,' and so decrease the air
space between the carbons. A state of
equilibrium will thus again be established
and the electric arc will have the same
brilliancy as before.
o; course in practice the action of the
solenoid is as gradual as the increase of the
space between the carbons, 50 that there is
no sudden up and down motion of the
carbon s'h.' If, however, there is solt
spot in either end of the two carbons, rapid
combustion Will take place and the carbon
"h" will drop suddenly. The solenoid
will at once act correspondingly
the carbon .'h'' will vibrate
for few seconds, causing a Pickering in
the light, till equilibrium is again estab-
lished and then all goes on as before. The
Pickering that we see in our street arc lights
is thus due, not to any electrical or mechan-
ical defects in the construction of the lamp,
but TO the uneven composition OF the car
bons.
THE SOURCE OF LIGHT.
1t must not be understood that the electric
arc is7yisible electricity. The passage of
the current from one carbon to another gen.
| crates great heat-that is, electric energy is
transformed into heat energy-and small
particles of carbon being set free, they become
incaudescent in this heat and give out an
intense white light. The ends of the car
5ons also become white hot, due to the heat.
The light, therefore, from an arc lamp
| comes from Two eOuiCCe, homSlyt bu6 WnlLe
hot carbon ends and the white hot carbon
particles or dust that is set free by the pas
sage of the current from one carbon to the
other. !"
1t is found that ii the current passes from
the upper carbon to the lower the upper car
bon will burn away much faster than the
lower; in fact, the current seems to tear of
particles from the upper carbon and deposit
them on the lower. This action tends to
make the end of the lower carbon somewhat
pointed and that of the upper carbon blunt,
as shown in the figure.
NATURE OF LIGHT.
Although we talk Of the electric light
yet, strange as it may sound, electricity doei
not produce light; neither do oils or gai
produce light In the oil lamp, the ga.
burner and the arc, or incandescent lamps,
light is produced in the same way. In each
case it is a transformation OF some form ol
energy into heat energy, and the heat pro