George Streynsham Master.

The Century, Volume 19 online

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As in either case the amount of electricity
flowing through a wire is in proportion to
the size of the wire, it will be readily seen
that the application of pressure made by
Mr. Edison obviates the main difiiculty in
the way of subdivision (/. ^., in the way
of the domestic use of the electric light),
namely, the enormous size and cost of con-
ductors. The well-known principle of the
effect of pressure upon the dynamic power
of electricity had never been utilized be-
cause the proper lamp was still unknown.
This lamp is Mr. Edison's main discovery.
In order to utilize this, one of the plans
devised by him was to make the flow
of electricity intermittent Enough was
allowed to escape in a short time, say one-
third, to keep the lamp all the time sup-
plied. It of course would require a large
wire to furnish the quantity of electricity
needed, yet two-tiiirds of the time the wire
would be inactive, during which period it
could be used to supply two other lamps con-
structed on the same principle. According
to the doctrine of probabilities, one-third of
a large number of lamps would be in use
all the time. Such being the case, the cost
of a conductor would be divided among
three lamps. The lamps were so constructed
as to bum steadily all the while, althcyugh
the electricity was passing tlirough them
only one-third of the time.



One form of apparatus for accomplishing^
this distribution among several lamps on the
same electrical circuit is shown in Fig. 6.
The current conducted by a single wire enters
the wire, O, from the lower left hand comer
and flows through the spring, S, by way of
Band B; upward through O', around the
magnets, M, M, and out through the lamp.
B, B, are two points where the circuit can be
broken if the spring, S, is depressed. Two
points are made in order that the spark
caused by the breaking of the circuit may
be made less by division. The spring S is de-




ne. 6. Edison's yibrathig RBOcrtATOK.
pressed by the arms, C, C, which are attached
to the armature. A, by the rod, R. The
action is as follows : The current renders the
magnet active, it attracts the armature. A,
and presses the spring, S, under, stopping the
flow of electricity by breaking the circuit at
B B. The magnet thus losing its power, the
armature is drawn back by the spring to
which it is attached and the apparatus is
ready to work again. The period of this
vibration may be regulated by means of a
screw underneath, which can make the ex-
cursion of the armature more or less before
it breaks the circuit, or can even act to break
the circuit itself.

In making an electric lamp which would
be efficient without a regulator (as is Mr.
Edison's later invention), two things are
essential, great resistance in the wire, and
a small radiating surface. Mr. Edison
sought to combme these two essential
conditions by using a considerable quan-
tity of insulated platinum wire wound like
thread on a spool. This arrangement is



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EDISON'S ELECTRIC LIGHT.



537



shown in Fig. 7. The spool was made of
zircon, pressed extremely hard, and was to
be suspended in an exhausted glass bulb by
two leading- wires.
The platinum, as
has been incident-
ally mentioned, was
hardened by alter-
nate heating and
cooling in vacuo^
which is done by
passing electricity
through it till white
heat is reached and
then cutting it sud-
denly ofif. A theory
is that the sudden
cooling con tracts the
metal and squeezes
out the air contain-
ed in it.

One of Mr. Edi-
son's greatest diffi-
culties was to ^et
a substance with
which to insulate his
wires that would not
melt and also be-
come a conductor in
the intense heat gen-
erated by the cur-
rent, — in which case
the electrical flow instead of traversing the
whole length of the wire would flow across
from layer to layer, or sidewise from wire to
.wire. This difficulty diverted his atten-
tion from platinum to carbon, which is
infusible. He did not suspect, at first, that
it could be made to offer sufficient resistance
to the passage of the electric current, and
that through it he was to reach a happy
solution of the entire problem. A long
time was spent, with a fair degree of success,
in seeking to make a spiral of lamp-black
tar in the form of a wire. To hold
this together he used a bit of ordinary
sewing cotton which was covered with
lamp-black, and succeeded in producing
from an inch and a half of this simple
thready bent into an arch, a light equal
to an ordinary gas-jet. The lamp-black,
however, contained air, which greatly inter-
fered with the success of the method. He
then used a simple thread, which he found
to answer the purpose, though it presented
the objection of being fragile, uneven in
texture, and unmanageable. This difficulty
suggested the use of charred paper, cut into
a tluead-like form. The difficulties appar-




Fia 7. SDfSON't PLATINUM
LAMP. HALP SIZE.



ently so insuperable melted away. The elec-
tric lamp was completed. A piece of charred
paper cut into horse-shoe shape, so deli-
cate that it looked like a fine wire, firmly



I



W



/w




PKL 8. BDISON's ■LlCnUC LAMP. EXACT tBB.



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EDISON'S ELECTRIC LIGHT.




FIG. 9. BnnCURY PUMPS FOSr PKODUCING VACUtTMS.



damped to the two ends of the conducting
and discharging wires so as to form part of
the electric circuit, proved to be the long-
sought combination. From this a light,
equal in power to twelve gas-jets, may be
obtained. Fig. 8.

The process by which the paper is ren-
dered serviceable is also extremely sim-
ple and inexpensive. The horse-shoe loops
are cut from card-board and placed m
layers, within an iron box, with tissue-
paper between; the box is hermetically
sealed, and then raised to a red heat. Noth-
ing remains but the carbon^loops and the
carbonized tissue-paper. All other forms of
carbon previously used had presented the
difficulty of containing air or gas. The car-



bonized paper, however, is found to be
perfectly homogeneous in structure, elastic,
tough, and of an almost vitreous cleavage.
It is strong enough to stand far more strain
than will be put upon it in any ordinaiy
use. If this paper were burned in air, or
in a vacuum prepared by a common air-
pump, it would of coiu"se be almost in-
stantly destroyed. In a high vacuum it
bums, but is never consumed. The smaU
glass globe which holds the simple appa-
ratus is exhausted of air by means of
nearly the same combination of the Spren-
gel and Geissler mercury pumps used by
Crookes in making his radiometer, or
" light mill," and in his wonderful discov-
ery of the phenomena of radiant matter in
high vacuums, recently brought before the
Royal Society of England. Much atten-
tion has been bestowed of late on the
question of securing good vacuums. An
absolutely perfect one is unattainable. It
is, however, found that, by the use of the
mercury pumps and chemical appliances,
where a nearly perfect vacuum is formed,
the minute portion of air remaining shows
some remarkable properties. When elec-
tricity understrong pressure passes through
an Edison lamp, the whole bulb shines
with a delicate blue light. So remarkable
is the behavior of various substances in a
vacuum prepared by means of mercury
pumps, that physicists consider that a gas
thus rarefied constitutes another state of
matter, diflfering as much from that of an
ordinary gas (either imder atmospheric
pressure or with the pressure removed by
means of a common air pump) as a gas
differs from a liquid, or a liquid fix)m a
solid. Mr. Edison's use of carbon in such
a vacuum is entirely new.

The pumps are shown in Fig. 9 ; the
Geissler pump is to the right and below. By
raising a bottle which is connected with it,
the air is forced out of a large glass bulb,
and allowed to escape through the tube A.
On lowering the bottle, the mercury flows
back into it, leaving a vacuum in the bulb.
The opening of a stop-cock allows some of
the air which is left in the pump to flow
into this bulb, when the air is again forced
out as described; this is continued until
the air is exhausted. The working prin-
ciple of the Sprengel pump is the contin-
uous dropping of mercury through a tube,
each drop acting as a piston, carrying
before it a small quantity of air. As there
is no return stroke, even by the aid of a
small tube, the work of exhaustion goes on



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EDISON'S ELECTRIC LIGHT,



539



quite rapidly. The MacLeod gauge in the
center is so constructed that it will measure
with exactness when less than one-mUlionth
of the original air is left in the pump.

Another purpose besides thpt of prevent-
ing the destruction of the carbon is served
by burning it in a vacuum. Almost all the
electricity is converted into light, very litde
being dissipated by convection or conduction
as heat The HtUe glass globe only an inch
from this brilliant light remains cool enough
to be handled, and does not scorch tissue-
paper wrapped closely around it.

Fig. 8 shows the lamp of its actual
size. The current enters it by one of the
wires, W. At B this copper wire is twisted
and soldered to a platinum wire,
which passes through the glass
at C, and by means of a small
platinum clamp into the horse-
shoe, L, from which, by as sim-
ple a route as it entered, it re-
turns. L, the source of light, was
made in the form of a hoise-shoe,
in order to approximate to the
shape of a gas-jet, and is large
enough to cause the edges of the
shadows to be softened down,
and so obviates the common
objection to familiar forms of
electric lighting. The carbon
is sealed in a glass bulb, G G G
G, the knob of glass, F, is the
melted extremity of the tube by
means of which the bulb was
connected with the pumps. At
the points, C, C, where the plati-
num wires are sealed into the
bulb, some trouble was occa-
sioned by the cracking of the
glass, which allowed air to leak
into the bulb. It will be noticed
that the glass is now drawn up
around the wire in a thin tube.
This is found to heat and cool
so rapidly that it is practically
homogeneous with the wire, and
even if the wire be heated red-
hot it will not break. Mr.
Edison has tried putting a lamp
alternately on and off the circuit
for several hours by means of a
telegraph key, without loosening
the wire. This experiment was
equivalent to using the lamp
several thousand times.

Mr. Edison has thus suc-
ceeded in making a lamp of the
simplest imaginable construc-



tion, and of materials whose expense is ex-
tremely small. The paper costs next to
nothing, the glass globes very little, and the
platinum tips of the wires are so small that,
though the metal used is expensive, their
cost is trifling. The test of the value of
every invention is its simplicity, and this is
the crowning characteristic of Mr. Edison's
lamp, for it is really nothing more than a
piece of wire looped into a glass globe.

The lamp being complete, let us consider
the generator [Fig. lo], for which Mr. Edi-
son has proposed the name Faradic, in
honor of the great physicist.

The cylinder which is placed below, be-
tween the blocks of iron, F, on which the



PIG. la PAKADIC CKNEXATOIt.



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540



EDISON'S ELECTRIC LIGHl.



magnets, M, rest, is called the armature, and
is so arranged that it can be made to revolve
rapidly by means of a belt. This armature
consists of a small cylinder of wood, which
is wound around with iron wire as thread is
wound on a spool, the ends being made
as in a spool, to hold the wire in place.
Around the whole spool are a number
of loops of copper wire, covered with
cotton thread, running lengthwise of the
armatiure. The ends of these loops may
be seen as they are taken from the
armatiwe to the cylinder, C, which is an
extension of the armature, by which the
currents generated in the copper wire may



which is pumped through the machine, may-
meet with as little friction as possible in pas-
sing through the wire of the armature, sinoe
by means of the ^eat strength of the mag-
nets, very litde wire can be made extremely
powerful in forcing the electricity to 3.
higher level or in putting it under pres-
sure. It is exactly as in pumping water,
if we have a poor pump (analogous
to a machine with a poor magnet) the
water may meet with an enormous fric-
tion in the pump itself, or require two or
more, perhaps, to give it the required pres-
sure, while in a good pump all the parts
are so made that while great pressure is



PIC. II. PROPOSED CBNTKAL STATION.



be taken away from the machine. This cyl-
inder, called the commutator, consists of
blocks of copper that really represent the
ends of the wire, which are placed side by
side around the axis of the cylinder in such
a manner that no current can pass from one
to the other. Touching these as they re-
volve are brushes, R, made of copper wire,
by means of which the electricity flows from
the machine.

That the wire about the armature may be
able to pump electricity into the line, it is
needful that it be revolved immediately in
front of magnets. The magnets are made
of such large dimensions that the electricity,



given to the water, it passes through it with
the utmost freedom. The machine has such
strength that it is intended to use only a
small fraction of the power, which it could
convert into electricity, and deliver outside.
It is proposed to mass a large number
of sucli machines, as in Fig. ii, and have
them all pump electricity up from one wire
into a second. The two large wires, held
on supports above the floor, are intended,
the one to carry the electricity away, and
the other to bring it back after it has been
used. Two machines are placed at one
side ; these are for the purpose of rendering
active the magnets of all the others.



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EDISOJ^S ELECTRIC LIGHT.



541



It is proposed to establish such stations in
tibe coiuse of a few months in the heart of
several of our large cities. These will sup-
ply houses for quite a distance around them.
I yooo horse-power is thought to be a suffi-
cient amount for a unit, and the stations




PIG. 13. DIAGRAM OP MBTBR AND SYSTBM.

will be at such distances from one another
that each district will require about this
amount. The engines will be divided into
four groups of 250 horse-power each, with
a spare one in each station of the same
power.

The wires will be laid in fascines or bun-
dles under the edge of the sidewalk in a
tight box. The object of this is to make
them easy of access and easy to
place in position. Nor is there
need of putting them out of the
reach of the frost, for they are
continuous and not liable to leak
from change in position. Even
more important is the fact that the
colder the wires are the less is the
waste of electricityi thus giving a
decided advantage over gas in
winter, when most light is needed.

The main wires may be either
of iron or copper according to
the market price of these metals ;
as quotations are to-day the prefer-
ence is slightly in favor of copper
wire. These lines of wire will start
from the central station and send
out branches in the same manner
that gas or water pipes diverge,
growing smaller the farther they are
removed from the central station.
Fig. 12 also shows the branch wires
as they enter the house. It is pro-
posed to color the distributing wires red and
the waste wires green. These two distinct
wires will be earned all through the house,
and every lamp will be so placed that the
electricity will flow through it from one wire
to the other.



Before passing into the house, the elec-
tricity is carried through a sort of meter con-
taining a safety-valve, by means of which
it can be measured. The contrivances for
doing this are shown in diagram, in Fig. i2|
and in perspective in Fig. 13. The lettering
is the same in both for identical
parts. The current enters at E,
passes through the two platinum
points, D, then through the arma*
ture, A, to the dividing points,
P P. ITie larger portion of the
current then flows around the mag-
net, M. The armature above the
magnet is held from it by means
of the spring, X. The object of
the device is to furnish a means of
cutting out a house if too large a
flow of electricity by any accident
should occur. The ma^et would
then be capable of drawing down the arma-
tiure which would separate the platinum
points, D, and break the circuit

The small wire, W, serves a double purpose
and is a remarkably clever solution of a
double problem. First : If the circuit were
partly opened it would weaken the magnet,
and the armature would recede, closing the
circuit It would thus form a vibrator




FIG. 13. EDISON'S BLBCTRIC UGHT MSTBB.



resembling Fig. 6. The wire, W, allows
enough electricity to pass to close the snap,
S, so that the armature is firmly held in
place, after which the wire, W, will melt off
and completely break the flow of electricity.
Secondly, the wire serves another purpose:



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EDISON'S ELECTRIC LIGHT.



if the points were drawn apart an arc would
spring between them. The wire, W, con-
ducts the electricity by a shorter route than
that offered by an arc and so keeps the
space between the two points free from the
intensely heated vapors of the metal.

A small fraction of the current passes by
another route to the lamps, from the point
P. It first traverses a length of wire wound
on small spools marked R. The amount
placed here will regulate the flow through
this line. The current next passes through
from one copper plate marked Cu to an-
other, through a solution of copper salt.
In thus flowmg, for every unit of current a
certain amount of copper is deposited on a
thin sheet, the amount for a lamp being once
determined by burning one for a number of
hours. It must be remembered that only a
smjall amoimt passes through the meter, but
that which passes is proportionate to the
whole. It is proposed to make a standard
lamp, which shall give a light equal to that
from a gas flame consuming five cubic feet
each hour. From this it will be calculated
how much copper will be deposited, and the
amount will besaid to represent five cubic feet
The bills for electricity will be made out in
1 ,000 feet, as in the case of gas. The inspec-
tor will take the strip on which the copper is
deposited to the central station, in order to
determine the amount of electricity used.

Besides giving light, the electncity sup-
plies a convenient form of motor for aomes-
tic purposes. A small electrical engine
placed beside a sewing-machine, for exam-



nC. 14. EDISON'S BLBCTKIC MOTOR.

pie, and connected with the distributing
wire, may save all the fatigue of treading
the machine, at an expense exactly equal to
that of one jet burning for the same time.
Elevators may be lifted, lathes turned, and
instruments operated up to several horse-



power, by this same means. Fig. 14 shows
the form adopted by Mr. Edison. It is
substantially a small model of the large
Faradic machine, the only change being in
the fact that the armature, C, is placed
lengthwise of the magnets, MM, instead of
across them. At S is a switch by means of
which the motor can be started or stopped.
It is expected that the amount of power
used in the day time will largely pay for
the expenses of generating — an addidonal
advantage over gas.

In order to use the lamp, it is brought
into the circuit by turning a handle in a
certain direction, or thrown out by reversing
the motion, or by means of plugs, which
are inserted in a socket This may be done
either in the chandelier or in any other
convenient place in the house. Very simple
arrangements may be made so that by
touchmg a knob by the bedside the whole
house may be brilliandy lighted for the re-
ception or discovery of a suspected burglar.
Of course, no matches have to be v^ed\
the hght kindles itself by the turning of a
handle, and so one fruitful source of de^
structive fires is avoided.

In order that the phUosophical relations
of the processes may be imderstood it is
needful to trace the history of the energy as
it is taken from the coal and conveyed over
the wire to the lamp. A large portion of
the heat produced by the combustion of the
coal under the boiler is found in the steam
as it flows to the engine. By means of the
latter a small fracrion, about ten per cent
of the onginal en-
ergy, is transformed
into the motion of
the wheels attached
to the engine. It
may be traced as
it flows through the
belt to the shaft,
-; and again as it is
carried from the
shaft to any ma-
chine which it may
drive. A belt ex-
actly resembles, in
carrying power, a
man pulling a shaft
around by means
of a rope. The amoimt he is pulling can
be measured by the strain on the belt, and
die work he is doing by determining the
speed with which he carries the end of
the rope. Mr. Edison has made a device, rep-
resented by Fig. 15, to measure this strain.



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ED/SON'S ELECTRIC LIGHT. 543



The belt starting
from the pulley
over the main
shaft, C, is carried
under a pulley, A,
which is attached
to a large box
containing heavy
weights. This box
is placed upon a
platform scale.
The belt then runs
over pulley, D,
which it has to
drive, and under a
wheel, B, which
rests heavily upon
what would other-
wise be the slack
part of the belt,
for the purpose of
tightenmgit. The
pulley , A, attached
to the weight, will
have a tendency to
be drawn upward
by any strain that
may be put on the
belt, just as the
block of a tackle
is drawn up when
the rope is tight-
ened which runs
through it The
weight Ufted may
be measured by
the diminution of
weight on the
scale, one half of
which gives the
strain on the belt.
Fig. 15 also shows
the arrangement
of machines as

they were placed "^ 'S- BDUON's UVNAMOMmK, TOK mASinaifO THB POBCB or AN KLBCnUC CUMtXNT.



in order to be tested. The cones D and E
were for the purpose of changing the speeds
at which the machines were run. The ma-
chine, H,at the right, renders active the field
of the other machine, F; the current may
be regulated by passing through more or
less of the resistance boxes, R. By means
of this apparatus the exact amount of power
carried by the belt can be reckoned when
its speed is known. This latter measure-
ment is made from the main shaft.

The energy which the belt carries is
seemingly lost, as material motion, when it
has turned the armatiu'e of the Faradic



machine. Since this seems to be a point
where the majority lose the track of the
energy, in order to explain clearly allu-
sion must be made to some fundamental
experiments. Arago many years ago tried
this experiment : a sheet of copper, which
is not attracted by the magnet under ordi-
nary conditions, was passed between the
two poles of a powerful magnet, and it was
found to be retarded in its motion. If the
magnets are extremely strong, though the
copper sheet to the eye passes through
nothing but air, yet to the hand it seems as
if it were cutting cheese, so strong is the



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''THAT LASS (7 LOWRIE'Sr



drag put upon the copper. This phenome-
non Tyndall calls the apparent viscosity
of the magnetic field. Faraday, a few years
after this discovery, clearly explained the
reason for seeming friction between the plate
of copper and the invisible lines of magnetic
force which he imagined to reach out from
every magnet He used wires and passed
them in front of the magnet, and found
that whenever they were made to cut these
lines electricity was thrown into the wire.
This grand discovery is at the basis of all
that is now done m making strong cur-
rents, for it furnishes the method by which
motion of mass may be transformed into the
molecular motion called electricity.

As the energy appears in the wire, it is
measured again by an electrical dynamom-
eter, the main idea of which was that of Pro-
fessor Trowbridge, of Harvard University.

By means of the two instruments, one is
enabled to trace out the amount of energy
absorbed and given back by the machine,
and in many cases ninety per cent of the
original power applied is found converted
into electricity. A system of electric light-
ing is nothing more than a gas system, where
energy takes the place of vapors.

It is one of the laws of progress, that no
sooner is a method for producing a cer-
tain result perfected than a practical use of



Online LibraryGeorge Streynsham MasterThe Century, Volume 19 → online text (page 92 of 160)