IMPROVEMENTS IN ELECTRIC LIGHTS, AND IN APPARATUS FOR DEVELOPING ELECTRIC CURRENTS AND REGULATING THE ACTION OF THE SAME
Year: 1879

page_text: LETTERS PATENT to Thomas Alva Edison, of Menlo Park, in the State of
New Jersey, United States of America, Electrician, for the Invention of
IMPROVEMENTS IN ELECTRIC LIGHTS, AND IN APPARATUS FOR DEVELOPING
ELECTRIC CURRENTS AND REGULATING THE ACTION OF THE SAME."
Sealed the 14th October 1879, and dated the 17th June 1879.
PROVISIONAL SPECIFICATION left by the said Thomas Alva Edison at the
Office of the Commissioners of Patents on the 17th June 1879.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United
States of America, Electrician. "IMPROVEMENTS IN ELECTRIC. LIGHTS, AND IN
APPARATUS FOR DEVELOPING ELECTRIC CURRENTS AND REGULATING THE ACTION
OF THE SAME."
I have ascertained that when wires or sheets of platina, iridium, or other
metallic conductors of electricity which fuse at a high temperature are exposed to
a high temperature near their melting point in air for several hours by passing a
current of electricity through them and then are allowed to cool, the metal is found
to be ruptured, and under the microscope there is revealed myriads of cracks in
every direction, many of which are seen to reach nearly to the centre of the wire.
I have also discovered that contrary to the received notion platinum and iridium
alloy loses weight when exposed to the heat of a candle, that even heated air causes
it to lose weight, that the loss is so great that it tinges a hydrogen flame green,
and under the influence of an electric current and at a yellow white heat the loss
is very great. After a time the metal falls to pieces, hence wire or sheets of
platinum, or platinum or iridium alloy, as now known in commerce, are useless for
giving light by incandescence.
V
First, because its loss of weight makes it expensive and unreliable, and causes
the burner to be rapidly destroyed.
Second, because its electrical resistance changes by loss in weight and its light
giving power by the cracks or ruptures, the melting point being determined by
the weakest spot where the greatest difference of potential of the electric current
is present, which causes this point to be brought to a higher beat than the rest of
the surface of the wire; again, as it is essential to obtain a steady light thê

page_text: platinum burner must be screened from the air, and when thus screened by being
placed in a glass vessel the glass soon becomes coated with a black deposit of
platinum.
A platinum spiral brought to incandescence under these conditions may be made
to give a light of three standard candles when near its melting point, and when the
radiating surface is 3/16 of an inch, but this amount of light will be rapidly reduced
as before described.
From my researches and experiments I am led to believe that the cause of the
rupturing of this metal when brought to incandescence is due to the action of the
gases contained in the pores of the metal. These gases are probably compressed
within the pores during the rolling or drawing of the sheet or wire.
These gases or air when subjected to high heats are greatly expanded and
rupture the metal, and it cannot be driven out by slowly heating the metal.
I have also discovered that the loss of weight and apparent volatilization of the
metal is due to the action of the air or gases against the highly heated surface.
Having thus ascertained the cause of fracture and loss of weight I have conducted
experiments to obviate these defects, and have succeeded by the following
method-
-A spiral of platinum wire is placed in a glass bulb, with its ends passing
through and sealed in the glass, and the air exhausted from the bulb by a Sprengel
pump, until the discharge from a three inch induction coil will not pass between
two subsiduary wires in the bulb, the ends of which are four millimetres apart;
the wires of the spiral are then connected to a magneto electric machine or battery
whose current can be controlled by the addition of resistance. Sufficient current is
allowed to pass through the wire to bring it to about 150° Fahrenheit; it is allowed
to remain at this temperature for 10 or 15 minutes; while thus heated the air or
gases in the pores of the metal is expelled by the action of the heat and the
expansion of the gases which tend to pass outward in consequence of the vacuum.
While this air or gases is passing out of the metal the mercury pump is kept con-
tinuously working. After the expiration of about 15 minutes the current passing
through the metal is to be augmented so that its temperature will be about 300
degrees Fahrenheit, and it is allowed to remain at this temperature for another 10
or 15 minutes. If the mercury pump be worked continuously and the température
of the spiral raised at intervals of 10 or 15 minutes until it attains to vivid incan-
descence, and the bulb be then sealed, the metallic wire is then in a state heretofore
unknown, for it may have its temperature raised to the most dazzling incandescence,
emitting a light of 25 standard candles.
Whereas before the treatment the same spiral would only emit a light equal to
three candles before attaining the melting point. The wires subjected to the
process of freeing them from air and gases are found after the process to have a
polish exceeding that of silver, and obtainable by no other means, no cracks can
be seen even after the spiral has been raised suddenly to incandescence many times
by the current, and no volatilization takes place as there is no deposit upon the
glass bulb, nor does a delicate balance show any loss of weight in the spiral after
burning for many hours continuously, because the spiral is in a vacuum that is so
nearly perfect that the action of the gaseous molecules is reduced to the minimum,
and were it possible to obtain an absolute vacuum there would be no loss what-
I have
soever, and the total loss after a year's use would scarcely be noticed.
further discovered that if an alloy of platinum and iridium, or even platinum be
coated with the oxide of magnesium in the manner hereafter stated, and subjected
to the vacuum process described, that combination takes place between the metal
and the oxide, giving the former remarkable properties. With a spiral, having a
radiating surface of 3/16 of an inch, light equal to that given by 40 standard candles
may be obtained, whereas the same spiral not passed through my process would
melt before giving a light of 4 candles.
The effect of the oxide of magnesia is to harden the wire to a surprising extent
and rendor it more refractory. A spiral spring made of the wire is as elastic and
springy when at dazzling incandescence as when cold.

page_text: I have found that chemically pure iron and nickel drawn in wires and subjected.
to the vacuum process may be made to give a light equal to that of platinum in
the open air.
Carbon sticks may be also freed from air in this manner and be brought to a
temperature, that the carbon becomes pasty, and if then allowed to cool is very
homogeneous, and hard rods or plates made of mixtures of finely divided con-
ducting and non-conducting materials, may thus be freed from air. It is also
obvious that the metal might be heated by subjecting the containing bulb to a
considerable temperature, but this only partially frees the wire from its air or
gases.
I will now describe the form of burner of lamp which I employ.
To operate several hundred electric lights practically, each equal to an ordinary
gas jet, upon one circuit, it is essential for many reasons, both on the score of
economy, facility, and reliability, to place them all in multiple arc, and to prevent
the combined resistance of several hundred lamps from falling to such a low point
as to require main conductors of immense dimensions with low resistance, and
generating machines of corresponding character, it is essential to reverse the present
and almost universal practice of using lamps which have but one or two ohms
resistance, and construct lamps which shall have, when giving their proper light, a
rosistance of several hundred ohms, because the more lamps there are in circuit the
less will be the resistance. I have ascertained by experiment that the loss of
energy is in proportion to the extent of the radiating surface independent of the
resistance of the conductor; hence we have 100 lamps, each of 1/4 of an inch
radiating surface, and each of 1 ohm resistance, or 1,000 lamps having the same
radiating surface and 1,000 ohms resistance each; the loss of energy from each
lamp, when giving each a light of 15 candles, will be nearly the same, but the
combined resistance of the 1 ohm lamps will be 100 of an ohm, requiring an enor-
mous main conductor, whereas the combined resistance of the 1,000 ohms lamp will
be 1 ohm, requiring a conductor of very moderate dimensions. In practice, a
resistance of 200 to 300 ohms in the burner will be sufficient.
Again, with lamps of low resistance, the lamp connections and leading wires
must be large to prevent great loss of energy by resistance, the leading wires from
the main conductors are large, expensive, and bulky to handle, the low resistance of
the burner or incandescent conductor requires large terminals to convey the current,
and these offer by their conduction a medium for the rapid dissipation of energy
without producing any effect, whereas with a lamp of high resistance all these
objections are obvinted.
My burner consists of a bobbin composed of an infusible oxide, such as oxide of
calcium, cerium, zirconium, magnesium, freed from silica, and turned in a latlic from
sticks moulded by hydraulic pressure in a manner hereinafter set forth.
These wires serve to hold the bobbin in the centre of the sealed glass vacuum
bulb and at the same time-serve as conductors of the electric current to the wire
coiled upon the bobbin.
The two platinum wires are first passed through small tubes of glass which are
melted round the wires. The burner is introduced into the bulb and the wires are
passed out through the sides of the narrow neck leading from the bulb, and the
glass is melted around them to prevent leakage, the glass of the neck being melted
to the small glass tube around the wires.
Before the burner is permanently scaled at the neck the air pump is connected
therewith and the wire upon the bobbin is subjected to the vacuum process hereto-
fore described, and the electric current is used to produce incandescence for about
one hour to heat the bobbin and thereby expel the air and gases, after which the
bulb is permanently sealed by melting the glass of the neck, and it is ready to bo
ised as a lamp.
.
The method which I adopt for regulating the light radiated from the burner
consists in a small rotating magnet provided with a governor which serves to open
he lamp circuit when the strength of the current is greater than is necessary to

page_text: produce the proper light in the bobbin. This apparatus is very reliable, and
although the current supplied is not perfectly continuous the total energy passing
to the lamp in one hour is nearly the same, no matter. what the strength of the
current may be. The magnets are so arranged that the continuous metallic circuit
cannot be broken by the commutator of the revolving magnet and the extra current
produced by the reversal of the current in the revolving magnet is short circuited
by the fixed magnet, hence the sparks which would occur at the break points of
the governor are prevented.
The rotating magnet is upon a vertical shaft supported in suitable bearings, and
immediately over the rotating magnet is the fixed magnet, the cores of which are
in the path described by the rotating magnet. Upon the shaft is a reversing
commutator formed of an insulated ring, the periphery of which is faced with
platina and cut in two parts, one part being connected by a wire to one helix of
the revolving magnet and the other part to the other helix of said magnet, the two
helices being connected. Rubbing on this ring are two contact springs which serve
to convey the currents to the revolving magnet.
The current passes through the fixed magnet, thence through the revolving
magnet, the rotation of the magnet being kept up by the reversal of the direction
of flow of the currents through the revolving magnet.
When the cores of the revolving magnet are nearest the cores of the fixed magnet
the direction of the flow of current is reversed by the action of the commutator
springs and commutator, and the polarity changed; hence the attraction ceases, but
the momentum of the revolving magnet carries said magnet forward, and mutual
attraction again takes place; as the revolving cores approach the stationary cores
the current is reversed and the revolution continued.
Connected to the revolving shaft is a governor which consists of two collars
connected together by two springs; one collar is secured to the shaft while the
other is free to slide thereon.
Upon cach spring a weight is secured, and the rotation of the shaft causes these
to act centrifugally, and bow outwards the springs, and raise the sliding collar
upward, more or less in proportion to the speed of the shaft.
The sliding collar is made with a groove to receive the end of the circuit opening
lever, which lever is moved by the rise and fall of the collar. The other end of tho
lever has an insulated cross bar which is in contact with two circuit breaking
springs, and serves to disconnect the springs simultaneously from their contact
points or blocks when the shaft has reached a certain velocity.
The object of using two springs is to open the circuit at two places simultaneously
and thus reduce the spark, which it does in the ratio of the number of simultaneous
breaks.
One of the two springs is connected by a wire to one of the commutator springs
and the other is connected to the wire leading from the main conductor or a branch
therefrom. This method of breaking the circuit simultaneously in many places is
applicable to all kinds of electrical apparatus where large and powerful sparks
occur, as, for instance, if it is desired to transfer electric energy from one point to
another by dynamo electric machines operating upon a magneto electric motor at a
distant station. If four springs are employed and the circuit opened at the four
places simultaneously the spark will be reduced to 1/10 of what it would be if it
was opened at but one place.
The block to which the two circuit breaking springs are secured is connected to
a screw so that said block and springs can be positioned or adjusted with reference
to the cross bar on the governor lever.
By turning this screw to the right the block and springs are moved until the
cross bar moves the springs away from their contact points or bars, and disconnects
the lamp from the circuit; the reverse movement places the lamp in circuit, and,
according to the proximity of the springs to the cross-bar of the governor lever, so
the amount of current to the burner is regulated. A stop is applied to the screw so
that it can be turned only to a determined point which limits the amount of current

page_text: passing to the burner. I prefer that each burner shall give a light equal to 16
candles, the burner being capable of giving 35 candle power without fusion.
As there may be a point where the revolving magnet, after being at rest, will not
start when the current is put on, I use an automatic starter which consists of a light
lever and thin armature turned edgewise, which is attracted by the fixed magnet
at the moment the current is put on. The movement of this lever, which carries
upon its end a click, serves to give a sudden motion to the shaft of the revolving
magnet by the click engaging in a rachet or toothed wheel secured to the shaft.
The click, after making this moveinent, passes beyond the ratchet and does not
come in contact again until the magnet is stopped and the current is broken.
In the Specification of my British Patent, No. 5306, of 1878, I have described the
manner of coating the wire with pyroinsulating material. I employ that mode in
coating the wire, after which a coil of said wire is wound upon one or more lime
supports and placed in a sealed bulb that is connected to a Spengel vacuum apparatus,
and by gradually increasing the heat of the wire by the gradual rise in the strength
of the current, as described in the first part of this Specification, the wire is not only
freed from air and rendered more refractory, but the oxide is vitrified and shrinks
upon the wire, from which it cannot be detached.
The coil, after passing through this process, may be wound upon the lime bobbin
of the lamp without breaking the pyroinsulation.
After the bobbin is wound and placed in the final bulb it has any air which may
have passed into the oxides expelled by a gradual accession of current in the manner
heretofore described, and the bulb is then sealed.
The oxides of the alkaline materials which are infusible attack the platina to a
slight extent, and, as herewith, greater tenacity to it than the oxides which do not
attack it, such as cerium or zirconium; but the compound thus formed renders the
wire more refractory.
It is not essential that the oxide should be in the form of a soluble salt, as it may
be put on the wire directly by mechanically mixing the oxide with water, alcohol,
or other liquids, but special devices are requisite to keep the mixture in constant
agitation to prevent settling.
It has been found very difficult to mould slender sticks of the oxides enumerated
on account of the bending and breaking of the plunger of the mould, which, owing.
to the pulverulent nature of most of the oxides, inust be long and slender.
I have obviated this difficulty by devising a mould and plunger by which
pressures to the crushing point of steel may be concentrated upon one quarter of an
inch surface.
This apparatus is applicable to the moulding of any substance.
The block that receives the mould is of cast iron, with a taper holo in the centre.-
The mould is made of three pieces, and has the same taper as the hole in the block.
The object of the taper and split mould is to allow the pressed piece to be taken
out without injury, which it would receive were it forced out of the mould endwise.
The plunger
upon the end of a sliding stock, and said plunger is only about
of an inch long and about 3/3 of an inch in diameter, and it is adapted to pass
downwardly into the hole in the centre of the split mould.
After the mould has been filled to the top with the pulverulent oxide a steel
washer or punch section is placed upon the oxide and forced into the mould by the
plunger. Afterward another punch section is placed upon the first one and forced
into the mould in the same manner. Thus sections may be added until the desired
pressure is obtained without any disarrangement of the apparatus. So powerful is
the pressure which may be obtained by this means that cylinders of the oxide of
magnesium are rendered semi-transparent.
The cylinder of oxide thus obtained is placed on a lathe and the bobbin turned.
with a cutting tool without fear of breaking.
:
The electric generating machine which I propose to use consists of a powerful
field magnet, between the poles of which rotate an induction bobbin.
The cores of the field magnet are each three feet in length and about six inches

page_text: in diameter, and wound with a helix of insulated copper wire having a resistance
of about one ohm.
The number of coils and the resistance of the wire may of course be varied to
suit various conditions. By the use of large masses of iron I am enabled to reduce
the resistance of the magnetic circuit to a very low point, and at the same time by
reason of this large mass of iron of great magnetic conductivity the use of a single
layer of wire is possible, thus obtaining the maximum economy.
The back or bar that connects the two cores of the magnet is of iron, and is
greater in mass than in the same length of core. The surface of both the back and
the end of each core are ground together, and are permanently secured by bolts
and nuts. By thus employing a large mass of iron for the back, and grinding the
faces of contact to a point where air suction becomes powerful, I reduce the resistance
of this point to a minimum and prevent the appearance of free inagnetic poles.
There are iron poles bolted to the cores, the surfaces being ground together.
Between the two poles there is a circular aperture in which the induction
cylinder rotates.
The cylinder may be of wood upon a shaft, and at each end of the cylinder there
is a wrought iron head.
This cylinder or bobbin is wound with fine wire until the wire is flush with the
edge of the iron heads.
Over this cylinder is wound longitudinally the insulated induction wire, the ends
of which are connected to the commutator. The wire of the parallel induction
helix is substantially endless, and it is wound with reference to obtaining a con-
tinuous current.
The number of parallel coils may be more or less in number, but I find the
desired object can be obtained by using an even number of parallel coils longi-
tudinally of the cylinder, and an odd number of the commutator plates.
There are two insulated discs upon the shaft of the field magnet, and a metallic
brush or spring is in contact with each disk; the line wires are connected to these
disks. One end of the wire of the field magnet is connected to one disk, and the
other end of the wire is connected with one of the commutator brushes; the other
commutator brush is connected with the second insulated disk.
The path of the current is through one insulated disk to the field magnet, through
it to one commutator block, then through the induction coil to the opposite block
on the commutator, and by brush and wire to the second insulated disk, and thence
to the line.
The current will be continuous, or nearly so, and travel in one direction; there
will however sometimes be a spark between the commutator bars when the circuit
of the parallel induction coil is interrupted, but this will be lessened by having the
commutator springs bent to rest on more than one commutator bar.
It will be apparent that the shell and parallel induction coil may be revolved if
the magnet cylinder remains stationary; and 1 remark that the cylinder supporting
the parallel induction coil may be of any suitable material, but I prefer vulcanized
fibre.
The parts of this machine are not liable to become heated under ordinary circum-
stances of use, because the wires are not wound one on the other and the atmo-
sphere has an opportunity to circulate.
I however apply a fan in some instances upon the shaft of the field magnet
within a case communicating with the internal portions of the machine, so as to
induce a current of air through the same.
As I have heretofore set forth the maximum economy of illuminating by elec-
tricity when using a great number of light giving points is only obtainable by
working the resistance in multiple arcs, hence it is also necessary that the gene-
rating machines should also be worked in multiple arc.
To work a great number of machines in multiple arc with economy and reli-
ability it is essential that all should have the same electro motive force, and that
means must be devised to prevent the insulating covering of the induction bobbin

page_text: of any machine being burned should the same stop for any reason, such as by the
breaking of a belt; because if the wire of the bobbin cease to be the seat of an
electro motive force the current from the other machines pass through it and tend
to produce sufficient heat to destroy the insulation, and at the same time cause a
loss of available energy.
I prevent any such action by the use of a polarized magnet, which prevents the
electric circuit being opened by the direction of the flow of the current from the
machine when in action tending to hold its tongue strongly against a contact point,
but if the machine should stop and cease to be the seat of an electro motive force, a
current from the other machines passes through the machine in a contrary direction,
whereupon the tongue of the polarized magnet is attracted from its contact point
and the circuit opened.
Each machine being provided with this apparatus, it is freed from the danger
aforementioned.
An ordinary magnet with its armature lever provided with a retractile spring
might replace the polarized magnet, but the margin for adjustment would be very
small.
The resistance of the polarized magnet is made an exceedingly small fraction of
the resistance of the machine to prevent loss of energy.
The field magnets of the machine are energized by supplying their helices with
electricity from thermo-electric piles.
Compound condensing steam engines are employed at the large central stations to
drive the magneto electric machines, and the heat given off from the surface con-
densers acts upon thermo-electric piles to produce an electric current, and the same
is passed through the field of force helices.
The field magnets may all be connected in multiple arc, and the thermo electric
piles arranged in the same manner with appliances whereby the strength of all the
field may be increased or decreased at pleasure, thus increasing or decreasing the
electro motive force of the induction bobbins, thus making it easy and convenient
by the aid of electro meters at the central stations to counteract the rise and fall in
the electro motive force on the main conductors when the maximum and minimum
number of lamps may be working.
'
I will mention that the electro motive force of the machine is analogous to the
pressure in the system of gas lighting and at dusk when the lamps are being rapidly
connected to the circuit the electro ineter will shew a slight drop on the electro
motive force or pressure, and this may be increased by increasing the speed of the
prime mover or increasing the power of the field magnets; the later method is the
one I prefer.
The surface condensers which I employ consists of a great number of iron pipes
whose surfaces are painted with a thick coating of a non-conducting substance. The
pipes after painting are about five inches in diameter.
Over these pipes are slipped rings of the double sulphide of lead and copper.
These rings are cast in a mould, and both the inner and outer edges are either covered
or plated with copper.
The inner copper ring of one disk connects with the outer copper ring of the
adjoining disk throughout the entire series of disks.
Owing to the exceedingly low resistance of these disks and the considerable
electro motive force which they give between the low range of temperature very
powerful currents are obtained, and nearly as much energy is thus obtained in the
form of an electric current from the waste heat of the engine as can be obtained
from the engine itself through the medium of the Faradic machines.
In British Letters Patent, No. 4226 of 1878, granted to me, a method is described
and shewn for measuring the total energy passing into the house of the consumer
during a given period of time, the same consisting of a depositing cell or cells in
which the weight of copper deposited by the current gives the indication.
Instead of the cell or cells shown two cells connected by a syphon may be used.
In one cell is a solution of cupric sulphite and a copper electrode, and in the other

page_text: cell sulphuric acid and a copper electrode. No polaziation takes place; the liquid
of the syphon tube offers the requisite resistance.
The cells are sealed from the air to prevent loss by evaporation.
Any loss by this means may be made good by adding water, the results are
nearly independent of the strength of the solution.
The central stations are intended to light an area of of a mile in every direc-
tion. The method which I propose to adopt for conveying the current from the
central station to various points, consists in laying double wrought pipes lined
with vulcanized rubber, known as ebonite, side by side under the flagging stones,
near the edge of the sidewalk. The pipes are to be 20 feet lenghts, the four ends
passing into a cast iron box.
The pipes and box are water-tight.
The top of the box, which is detachable, has its upper surface oven or flush with
the walk; from the same box small tubes serve to convey wires from the main
conductors to the houses of the consumers.
The wires forming the main conductors are small, and may either be insulated
and laid loosely together or insulated with a thin layer of cotton. In this case each
consumers wire will be independent, but the economy is greater when the wires are
all in contact, as then when few lamps are in use the resistance of the main con-
ductor is relatively small as compared to the lamps.
The practice of causing the total resistance of the circuit extraneous to the
generator to be equal to that of the generator, and by which the maximum effect is
obtained from the machine, is very wasteful of energy; for by thus arranging the
resistances fifty per cent. of the energy is lost in the machine itself, whereas if the
exterior resistance is four times greater than the machine the capacity of the
machine to translate energy from one to the other is lessened, but of what is trans-
lated, owing to the changed conditions, 80 per cent. may be utilized.
For this reason I so arrange the resistance of the main conductors that they
should be but /10 of the total resistance of all the lamps, and the resistance due
to the generating machine is kept down by keeping in multiple are a greater
number of machines than is necessary to supply all the lights which may happen
to be in circuit at the time.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Alva Edison in the Great Seal Patent Office on the 17th
December 1879.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United
States of America, Electrician. "IMPROVEMENTS IN ELECTRIC LIGHTS, AND IN
APPARATUS FOR DEVELOPING ELECTRIC CURRENTS AND REGULATING THE ACTION
OF THE SAME."
I have ascertained that when wires or sheets of platina, iridium, or other
metallic conductors of electricity which fuse at a high temperature are exposed to a
high temperature near their melting point in air for several hours, by passing a.
current of electricity through them, and then are allowed to cool, the metal is found
to be ruptured, and under the microscope thero is revealed myriads of cracks in
every direction, many of which are seen to reach nearly to the center of the wire.
I have also discovered that contrary to the received notion, platinum or platinum
and iridium alloy loses weight when exposed to the beat of a candle, that even
heated air causes it to lose weight, that the loss is so great that it tinges a hydrogen
flame green, and under the influence of an electric current and at a yellow white
heat the loss is very great. After a time the metal falls to pieces, henco wire or
sheets of platinum or platinum and iridium alloy as now known in commerce are
useless for giving light by incandescence, 1st., because its loss of weight makes it
expensive and unreliable, and causes the burner to be rapidly destroyed. 2nd,
because its electrical resistance changes by loss in weight and its light giving
power by the cracks or ruptures, the melting point being determined by the
weakest spot where the greatest difference of potential of the electric current is
present which causes this point to be brought to a higher heat than the rest of the
surface of the wire. Again, as it is essential to obtain a steady light the platinum*
burner must be screened from the air, and when thus screened by being placed in a
glass vessel, the glass soon becomes coated with a black deposit of platinum. A
platinum spiral brought to incandescence under these conditions may be made to
give a light of three standard candles when near its melting point, and when the
radiating surface is 3/10 of an inch, but this amount of light will be rapidly reduced
as before described.
From my researches and experiments I am led to believe that the cause of the
rupturing of the metal when brought to incandescence is due to the action of the
gases contained in the pores of the metal. These gases are probably compressed
within the pores during the rolling or drawing of the sheet or wire.
These gases
or air when subjected to high heat are greatly expanded and rupture the metal,
and it cannot be driven out by slowly heating the metal.
I have also discovered that the loss of weight and apparent volatilization of tho
metal is due to the action of the air or gases against the highly heated surfaco.
Having thus ascertained the cause of fracture and loss of weight, I have conducted
experiments to obviate these defects and have succeeded by the following method.
A spiral of platinum wire is placed in a glass bulb with its ends passing through
and sealed in the glass, and the air exhausted from the bulb by a Sprengel pump until
the discharge from a three inch induction coil will not pass between two subsiduary
wires in the bulb, tho ends of which are four millimetres apart. The wires of the
spiral are then connected to a magneto electric machine or battery whose current
can be controlled by the addition of resistance. Sufficient current is allowed to
pass through the wire to bring it to about 150° Fab., it is allowed to remain at this
temperature for 10 or 15 minutes. While thus heated, the air or gases in the pores
of the metal are expelled by the action of the heat and the expansion of the gases
which tend to pass outward in consequence of the vacuum.
.
While the air or the gases are passing out of the metal the mercury pump is

page_text: kept continuously working. After the expiration of about fifteen minutes the
current passing through the metal is to be augmented so that its temperature will
be about 300° Fahr., and it is allowed to remain at this temperature for another ten
or fifteen minutes. If the mercury pump be worked continuously, and the
temperature of the spiral raised at, intervals of ten or fifteen minutes until it attains
vivid incandescence, and the bulb be then sealed, the metallic wire is then in a
state heretofore unknown, for it may have its temperature raised to the most
dazzling incandescence, emitting a light of twenty-five standard candles, whereas
before treatment the same spiral would only emit a light equal to three candles
before attaining the melting point. The wires subjected to the process of freeing
them from air and gases are found after the process to have a polish exceeding that
of silver, and attainable by no other means; no cracks can be seen even after the
spiral has been raised suddenly to incandescence many times by the current, and no
volatilization takes place as there is no deposit upon the glass bulb, nor does a
delicate balance shown any loss of weight in the spiral, even after said spiral has
been burning for many hours continuously, because the spiral is in a vacuum so
nearly perfect that the action of the gaseous molecules is reduced to the minimum,
and were it possible to obtain an absolute vacuum there would be no loss
whatever.
C
I have further discovered that if an alloy of platinum and iridium, or even
platinum, be coated with the oxide of magnesium in the manner hereafter stated,
and subjected to the vacuum process described, that combination takes place between
the metal and the oxide, giving the former remarkable properties. With a spiral
having a radiating surface 3/16 of an inch, light equal to that given by forty standard
candles may be obtained, whereas the same spiral not passed through my process
would melt before giving a light of four candles. The effect of the oxide of
magnesia is to harden the wire to a surprising extent and render it more
refractory.
A spiral spring made of the wire is as elastic and springy when at dazzling
incandescence as when cold.
I have found that chemically pure iron and nickel drawn in wires and subjected
to the vacuum process may be made to give a light equal to that of platinum in the
open air.
Carbon sticks may be also freed from air in this manner and be brought to a
temperature that the carbon becomes pasty, and if then allowed to cool is very
homogeneous and hard. Rods or plates made of mixtures of finely divided con-
ducting and non conducting materials may thus be freed from air.
It is also obvious that the metal might be heated by subjecting the containing
bulb to a considerable temperature, but this only partially frees the wire from its
air or gases.
I will now describe the forin of burner or lamp which I employ. To operate
several hundred electric lamps practically, each equal to an ordinary gas jet, upon
one circuit, it is essential for many reasons, both on the score of economy, facility,
and reliability to place them all in multiple arc, and to prevent the combined
resistance of several hundred lamps from falling to such a low point as to require
main conductors of immense dimensions with low resistance, and generating
machines of corresponding character, it is essential to reverse the present and almost
universal practice of using lamps which shall have but one or two ohms resistance, and
construct lamps which shall have, when giving their proper light, a resistance of several
hundred ohms, because the more lamps there are in the circuit the less will be the
resistance. I have ascertained by experiment that the loss of energy is in propor-
tion to the extent of the radiating surface independent of the resistance of the
conductor; hence we have 1,000 lamps, cach of 1/, of an inch radiating surface, and
each of one ohm resistance, or 1,000 lamps having the same radiating surface and
1,000 ohms resistance each, the loss of energy from each lamp when giving each a
light of fifteen candles will be nearly the same, but the combined resistance of the
one ohm lamps will be robo of an ohm, requiring an enormous main conductor,

page_text: whereas the combined resistance of the 1,000 ohm lamps will be one ohm, requiring
a conductor of very moderate dimensions. In practice a resistance of 200 to 300
ohms in the burner will be sufficient. Again, with lamps of low resistance the lamp
connections and leading wires must be large to prevent great loss of energy by
resistance; the leading wires from the main conductors are large, expensive, and
bulky to handle; the low resistanee of the burner or incandescent conductor requires
large terminals to convey the current, and these offer by their conduction a medium
for the rapid dissipation of energy without producing any effect, whereas with a
lamp of high resistance all these objections are obviated.
My burner b consists of a bobbin composed of an infusible oxide, such as oxide of
calcium, cerium, zirconium, magnesium, freed from silica and turned in a lathe from
sticks molded by hydraulic pressure in a manner hereinafter set forth, and upon this
bobbin fine wire of platinum or platinum-iridium alloy is coiled. This bobbin is
shown in Fig. 1; it is secured to two platinum wires 1, 2, as in Fig. 2. These wires
serve to hold the bobbin in the center of the sealed glass vacuum bulb, and at the
same time serve as conductors of the electric current to the wire coiled upon the
bobbin. Fig. 3 shows the manner of connecting the wire upon the bobbin to the
platina supports. The two platina wires 1, 2, are first passed through a small tube
a of glass, and the glass melted around the wires. The burner b is introduced into.
the bulb c, and the wires 1 & 2 are passed out through the sides of the narrow neck
leading from the bulb, and the glass is melted around them to prevent leakage; the
glass of the neck is melted to the small glass tube a. Before the burner is perma-.
nently sealed at the neck the air pump is connected therewith and the wire upon
the bobbin is subjected to the vacuum process heretoforo described, and the electric
current is used to produce incandescence for about one hour to heat the bobbin, and
thereby expell the air and gases, after which the bulb is permanently sealed by
melting the glass of the neck, and it is ready to be used as a lamp, as represented in
Fig. 4.
The method which I adop for regulating the light radiated from the burner
consists in a small rotating magnet provided with a governor, which serves to open
the lamp circuit when the strength of the current is greater than is necessary to
produce the proper light in the bobbin. This apparatus is very reliable, and
although the current supplied is not perfectly continuous the total energy passing
to the lamp in one hour is nearly the same, no matter what the current strength
may be, the magnets being so arranged that the continuous inetallic circuit cannot
be broken by the commutator of the revolving magnet, and the extra current
produced by the reversal of the current in the revolving magnet is short circuited
by the fixed magnet, hence the sparks which would occur at the break-points of the
governor are prevented. Referring to Fig. 4, b is the bobbin with the platinum
iridium wire which forins the electric lamp, c is the sealed glass bulb; f and g are
supports to hold the bulb in position; these are insulated from each other.
platinum wires 1 and 2 from the bulb are connected to these supports.
The
m is a box for supporting the lamp and enclosing the governor; n is the back of
the fixed magnet, consisting of the spools o, o'; P, p', are the spools of the revolving
magnet is the back of the same, which is secured permanently to the shaft q,
upon which is a revolving commutator 8. This commutator consists of a ring of
insulating material, whose periphery is faced with platina and cut in two parts,
one part being connected by the wire 5 to the magnet pl, and the other part by
the wire 4 to the magnet p. The wire 65 connects the two spools p and p¹
together.
Rubbing on this ring are two contact springs 8', t', which serve to convey the
currents to the revolving magnet. The current passes through the fixed magnet
o, o', see diagram Fig. 5; thence by wires 4, 5, springs s, t, through the revolving
magnet p, p. The rotation of the magnet is kept up by the reversal of the direction
of the flow of the currents through the revolving magnet. When the cores of the
revolving magnet are nearest the cores of the fixed magnet the direction of the
current through the former is reversed by the action of the springs 8', t¹, upon the

page_text: commutator and the polarity changed, hence the attraction ceases; but the
momentum of the magnet p, p, carries it forward, and mutual attraction again takes
place; as the revolving cores approach the stationary cores the current is, reversed
and the revolution continued.
Connected to the revolving shaft q is the governor, which consists of two collars
v, w, connected by springs 6 & 7, the collar v is permanently secured to the shaft,
while the collar w is free to slide up and down upon it. Each spring is provided
at its center with a weight, and these weights act centrifugally to bow outwardly
the springs and raise the collar w upwardly more or less in proportion to the speed
of revolution. Connected to w by a sleeve is another collar 19, upon the surface of
which rests the end of the circuit opening lever l, which rises and falls by the
action of the governor.
A spiral spring, see Fig. 5, on the axis of the lever
serves to keep in contact with 19. Upon the extreme end of the lever is a
block 18 in juxtaposition to circuit breaking springs 8 & 9, and serves to disconnect
the springs simultaneously from the metallic block 10, when the governor and
shaft has reached a certain velocity. The block 10 is insulated from the frame 11,
and serves to keep the circuit closed between the springs.
The current passes by wire 84 to the spring 8, thence across the block 10 to the
spring 9, thence to the magnet and lamp by wire 85.
The object of employing two springs is to open the circuit in two places simul-
taneously and thus reduce the spark, which it does in the ratio of the square of tho
number of simultaneous breaks. This method of breaking the circuit simultaneously
in many places is applicable to all kinds of electrical apparatus where large and
powerful sparks occur; as for instance, if it is desired to transfer electric energy from
one point to another by dynamo electric machines, the distant machine, which serves
to give out the power for driving machinery, may be provided with a governor the
same as herein shown, and the circuit may be opened in several places simultaneously
by the action of the governor shown in Fig. 6. is the lever operated by the
governor; 12 and 13 are contact springs, which rest upon the bar 43; 14 and 15
are also contact springs which rest on the bar 44. The current passes by wire 84
to spring 12, across the bar 43 to spring 13, thence by wire 45 to spring 14, across
bar 44 to spring 15 to wire 85. When the governor reaches a certain velocity the
insulated piece 18 of the lever l'comes in contact with all the springs simultaneously
and separates them from the bars 43 & 44, thus opening the circuit in four places
simultaneously, the spark is reduced to 1/10 of what it would be if a single break
was used. Having shown the importance of breaking the circuit simultaneously
in many places will now describe how the illumination of the burner & may be
increased or decreased, or stopped entirely.
Referring to Figs. 4 & 5 t is the thumb nut for regulating the speed of the
revolving magnet and consequently the amount of energy which passes to the
burner. The nut 22 is provided with a slot or groove containing a stationary
pin 2, and into the nut 22 the screw 20 passes, and by turning this screw the
block 10 may be drawn inwardly or forced outwardly, said block running on two
guide pins 23, 24, which prevent the block from turning; thus the block 10 may be
made to approach or recede from the lever l.
If it is desired to turn off the light and disconnect the lamp altogether from the
circuit, the screw is turned to the right until the block 18 separates the springs 8
& 9 from the block 10 and opens the circuit. In this position the circuit is broken
and the lamp and magnets are entirely disconnected from the circuit.
If it is desired to have the lamp give light the screw is turned to the left; when
the springs 8 & 9 come in contact with the block 10 and close the circuit, the
magnets immediately revolve; and if the parts are left in such a position that the
piece 18 is in close proximity to the springs, the rotation of the magnet will operate
the governor and lessen the pressure of 8 and 9 on 10. and hence the speed will be
comparatively slow and the electricity passing to the light will be very small and
but little light will be given out, but by causing the block 18 to further recede
-

page_text: from 8 & 9 the speed of the magnet will increase and more energy will pass to the
lamp in a given time.
•
By continued turning of the screw 20 a point may be reached where the .
governor lever will not separate the springs 8 & 9 from 18; in this case the entire
electric energy passes through the bobbin b, but in practice limiting stops are
applied so that when the screw has been turned a certain distance the further move-
ment will be prevented by the action of the stops, thereby determining the
maximum light which the consumer can obtain from the burner. In practice this.
will be about sixteen candle power, the burner being capable of giving thirty five
candle power without fusion.
As there may be a point where the revolving magnet after being at rest will not
start when the current is put on I use an automatic starter which consists of a light
lever and thin armature turned edgewise which is attracted by the fixed magnet at
the moment the current is put on. The movement of this lever which carries upon
its end a click serves to give a sudden motion to the shaft q by the click engaging
in a ratchet or toothed wheel which is secured to it. The click after this move-
ment passes beyond the ratchet and does not come in contact again until the magnet.
is stopped and the current is broken.
In the Specification of my British Patent, No. 5300, of 1878, I have described
the manner of coating the wire with pyroinsulating material; I employ that mode
in coating the wire after which a coil of said wiro is wound upon one or more
bobbins and placed in a sealed bulb, and connected to a vacuum apparatus, and by
gradually increasing the heat of the wire by the gradual rise in the current strength,
as described in the first part of this Specification, the wire is not only freed from
air and rendered more refractory, but the oxide is vitrified and shrinks upon the
wire from which it cannot be detached. The coil after passing through this process
may be wound upon the lime bobbin of the lamp without fear of breaking the
pyroinsulation. After the bobbin is wound and placed in the final bulb any air
which may have passed into the oxides is expelled by a gradual accession of current
in the manner heretofore described, and the bulb is then sealed. The oxides of the
alkaline materials which are infusible attack the platina to a slight extent and
adhere with greater tenacity to it than the oxides which do not attack it, such as
cerum or zirconium, but the compound thus formed renders the wire more refractory.
It is not essential that the oxide should be in the form of a soluble salt, as it
may be put on the wire directly by mechanically mixing the oxide with water,
alcohol, or other liquids, but special devices are required to keep the mixture in
constant agitation to prevent settling.
It has been found very difficult to mold slender sticks of the oxides spoken of
on account of the bending and breaking of the plunger of the mold, which owing
to the pulverulent nature of most of the oxides must be long and slender.
I have obviated this difficulty by devising a mold and plunger by which pressures
to the crushing point of steel may be concentrated upon one quarter of an inch
surface. This apparatus is applicable to the molding of any substance, and it is
shown by a vertical section in Fig. 7. Fig. 8 is a plan of the divided mold. a³ is
the plunger; upon the extreme end is the part which enters the die or mold.
This is only about one quarter of an inch long and about three eighths of au inch
in diameter, and it is adapted to pass downwardly into the mold.
is a solid block of cast iron with a taper hole in its center, and into this the
divided steel mold f is forced; this mold is made of three pieces, and has the same
taper as the hole in the block c³. The object of the taper and divided mold is to
allow the pressed piece to be taken out without the injury it would receive wero.
it forced out of the mold end wise. After the mold has been filled to the top with
the pulverulent oxide a steel washer or plunger section is placed upon the oxido
and forced into the mold by the plunger; afterwards another plunger section is
placed upon the first one and forced into the mold in the same manner.
sections may be added until the requisite pressure is obtained without any
Thus

page_text: lisarrangement of the apparatus. So powerful is the pressure which may be obtained
by this means that cylinders of the oxide of magnesium are rendered semi-
transparent. The cylinder of oxide thus obtained is placed in a lathe, and the
bobbin turned with a cutting tool without fear of breaking.
The electric generating machine which 1 propose to use consists of a powerful
field magnet between the poles of which rotate an induction bobbin. This
apparatus is shown by a vertical section in Fig. 9, and sectional plan Fig. 10. F is
the field magnet, the cores of which are about three feet in length and tho
diameter about six inches, wound with a helix of insulated copper wire having
a resistance of about one ohm. The number of coils and the resistance of
the wire may of course be varied to meet various conditions. By the use of
large masses of iron I am enabled to reduce the resistance of the magnetic circuit
to a very low point, and at the same time by reason of this large mass of iron
of great magnetic conductivity the use of a single layer of wire is possible, thus
obtaining the maximum economy. a³ is the back of the magnet, and the mass of
iron is greater than in the same length of core.
The surface of both the back and
the end of each core are ground together and are permanently secured by bolts and
nuts. By thus employing a large mass of iron for the back and grinding the faces
of contact to a point where air suction becomes powerful, I reduce the resistance
of this point to a maximum and prevent the appearance of free magnetic poles;
, a, are iron poles bolted to the cores, the surfaces being ground together.
Between the two poles there is a circular aperture in which the induction cylinder
rotates. The cylinder b³ is preferably of wood upon the shaft b, and has wrought
iron heads b. This cylinder is wound with fine iron wire be until the wire is
flush with the edge of the iron heads b³. Over this cylinder is wound lougitudinally
the insulated induction wire in sections, the ends of which are connected to the
commutator it, as in Fig. 11. There are heads e³ of hard rubber, vulcanite, fiber, or
equivalent material secured to the shaft b', see Figs. 16 and 17, outside the heads 65,
and are of larger diameter, so that the induction wires e that are wound longi-
tudinally may be kept from contact with the iron helix 6 or heads 65, so that
the current may not be short circuited even if the insulation of the induction wires et
is imperfect. e is a pulley for driving the machine; e is a loose pulley upon
which the belt from the driving shaft is thrown by a shifter when the machine is
to be stopped.
3 is a switch by means of which the circuit from the Faradic machine may be
opened; and d are the commutator springs; ³ is a polarized magnet included
in the circuit, which serves automatically to open the circuit should a reverse
current be sent through the machine. The connections are as follows:-From the
post to the commutator it, thence through the induction helix e' to the opposite
side of the commutator, and by the brush to the switch ; thence to the tongue
of the magnet 3, if the switch lever is in contact with ; thence through the
tongue of ³ to the point i³, and through the magnet to the post . The wire
upon the field magnet is connected to the clamping posts 13 and 1'.
I will now
describe the method of winding the induction cylinder and the direction of the
current relative to the commutator brushes-The wire of the parallel induction
helix is substantially endess, and it is wound with reference to obtaining a con-
tinuous current. The diagram, Fig. 11, illustrates the manner of winding the
wires; the number of parallel coils may be more or less than that shown, but I
find the object desired can be attained the best by using an even number of
parallel coils longitudinally of the shaft, and an odd number of commutator plates.
Starting, say, from the part of the commutator, the wire passes to the space +
on one head e³ to the same space on the other head, then across the head to the
space 11, and to the same space on the other head, then across the head to the
space 4, and so on until the spaces 4 and 11 are filled with the wire, and when
the last turn in 11 has been laid the wire is led to the plate c, and then the spaces
2 and 9 are filled, and the wire from 9 led to d; then 14 and 7, and a connection inade

page_text: with e; then 12 and 5, connecting with f; then 10 and 3, connecting with g; then
8 and 1, connecting with a; then 6 and 13, connecting with b, the place of beginning.
I wind the wires in such a manner that while the current is continuous, and the
current flowing through the whole of it, the current will pass by two wires of the
induction coil to one commutator plate, and then away, and will enter by an
opposite commutator plate, and pass by two wires out into the coil, and circulato
through the same to the other commutator plate. Suppose the springs to rest upon.
commutator plates a and c the current will flow towards a from wires 1 and. 6,
and away from c by wires 12 and 7. By following the arrows it will be found that
the entire coil is a complete circuit, in which the parallel portions of the wires in
the south field of magnetic influence have a current energized in one direction,
and in the north field in the other direction, thus obtaining the dynamic effect,
and there is no break or pulsation of the current; the springs touch one com-
mutator before leaving another.
As I have heretofore set forth, the maximum economy of illuminating by
.clectricity when using a great number of light giving points is only obtainable by
working the resistance in multiple arc, hence it is essential that the generating
machines should also be worked in multiple arc. To work a great number of
machines in multiple-arc with economy and reliability, it is essential that all should
have the same electromotive force, and that means must be devised to prevent
injury by burning, to the insulating covering of the induction coil of any machine,
should said machine stop for any reason, such as by the breaking of a belt, because
if the wire of the induction coil ceases to be the seat of an electro-motive forre, tho
current from the other machines pass through it and tend to produce sufficient heat
to destroy the insulation, and at the same time cause a loss of available energy.
..
I prevent any such action by the use of the magnet h³, Fig. 10, which being
polarized, is prevented from opening the electric circuit by the direction of the flow of
current from the machine when in action, tending to hold its tongue strongly
against the contact point ; but if the machine should stop and cease to be the
seat of an electro-motive force, a current from the other machine tends to pass
through the machine in a contrary direction, whereupon the tongue of h³ is detached
from the point, and the circuit opened. Each machine being provided with this
apparatus is thus freed from the danger described. An ordinary magnet might
replace the polarized one, and a retractile spring used, but the margin for adjust-
ment would be very small.
The resistance of the magnet h³ is made an exceedingly small fraction of the
resistance of the machine to prevent loss of energy.
The field magnets of the machine are energized by supplying them with electricity
from thermo electric piles.
Compound condensing steam engines are employed at the large central stations
to drive the magneto electric machines, and the heat given off by the surface con-
densers act upon the thermo electric piles to produce an electric current, and the
same is passed through the field of force helices.
The field magnets may all be arranged in multiple are, and the thermo electric
piles arranged in the same manner with appliances, whereby the strength of all
the field inagnets may be increased or decreased at pleasure, thus increasing or
decreasing the electro motive force of the induction bobbins, thus making it easy
and convenient by the aid of electrometers at the central stations to counteract
the rise and fall in the electro motive force on the main conductors, when the
maximum and minimum number of lamps may be working.
I will mention that the electro-motive force is analogous to the pressure in the
system of gas lighting, and at dusk when the lamps are rapidly being connected to
the circuit, the electrometer will show a slight drop on the electro motive force or
pressure, and this may be increased either by increasing the speed of the prime
mover, or an increase in the power of the field magnets, the latter method is the
ono I prefer.
The surface condensers which I employ consist of a great number of iron pipes

page_text: whose surfaces are painted with a thick coating of a non-conducting substance
The pipes after painting are about five inches in diameter. Over these are slipped
rings of the double sulphide of lead and copper. These rings are cast in a mold,
and both the inner and outer edges are either covered or plated with copper. In
Figs. 12 and 13, m³ is the ring or disk of double sulphide; m, the copper ring
fitted in the hole of m³; m³ is a copper ring which fits over the circumference of
m³ to this ring a binding post and strip or wire m³ is secured, the latter to connect
to the next disk. m² represents one of the condensing pipes.
m³, m³, m¹º, & m", a series of disks arranged to give a current. The inner copper
of m³ connects to the outer copper of m³, and in this manner to many hundreds of
disks. Owing to the exceedingly low resistance of these disks, and the considerable
electro motive force which they give between low ranges of temperature, very powerful
currents are obtained, and nearly as much energy obtained in the form of an electrical
current from the waste heat of the engine as can be obtained from the engine
itself through the medium of the Faradic machines.
The central stations are intended to light an area of 1/4 of a mile in every direction.
The method which I have adopted for conveying the current from the central station
to various points consists in laying double wrought pipes, lined with vulcanized
rubber known as ebonite, side by side under the flagging stones near the edge of the
sidewalk. The pipes are to be in twenty feet lengths, the four ends passing into a
cast iron box. The pipes and box are water tight. Fig. 14 is a vertical section of
one line of pipe, and Fig. 15 is a perspective view representing the box and two
lines of conductors.
For electric lighting purposes I employ a main conductor m, composed of many
wires uninsulated from each other, but insulated as a whole from the earth by the
ebonite coating of the pipe p; but for telegraphic purposes each of the small wires,
instead of acting as parts of one main conductor, are to be insulated from each other
by being coated with cotton and afterwards passed through an insulating substance,
such as resin, tar, paraffine, or other non-conductor.
By first pulling down pipes p in sections of, say, twenty or twenty five
feet, and boxes between the sections, wires may be introduced sufficient
for the purpose at the time, and in the future the number of wires may be
increased by drawing others through the pipes. The boxes b allow for introducing
or guiding the wires by hand. In practice it will be preferable to employ small
pulleys in each box, with a stout cord running backward and forward through
the line of pipe for drawing the wire through each section. The box has a
cover c which is bolted to it, and soft rubber or oiled leather washers are placed
between the top and the box to prevent air or water leaking into the box.
The
inside of the box and cover is to be lined with ebonite or other non-conducting
waterproof material. One end of the system of tubes passes into the central station,
and if the other ends are closed a vacuum may be produced within the whole system
of pipes; this will promote the evaporation of any moisture which may have passed
into the pipes, but the vacuum will only be required periodically. If the two ends
pass into central stations warm dry air may be passed through occasionally to
prevent dampness. In the system of electric lighting two lines of pipes are
employed on each side of the street, but these may be separate and have independent
boxes. 1 prefer that both lines of pipes on cach side of the street should be con-
nected to one range of boxes, as illustrated in Fig. 15. A small pipes insulated
with rubber is connected at right angles to the main pipes, and passes from one of
the boxes into the house to be illuminated, and carries the conductor, which may be
made of one or more wires. From the other main conductor another small tube s
serves to carry the second wire to the house. These wires, entering the house
through the meter, are carried into various rooms, and the electric lamps connected
in multiple are between the two. The wires forming the main conductors are small,
and, as. mentioned previously, may be uninsulated and laid loosely together, or
insulated with a thin layer of cotton. In the latter case each consumer's wire would
be independent, but the economy is greater when the wires are all in contact, as

page_text: C
then, when few lamps are in use, the resistance of the main conductor is relatively
small as compared to the lamps. The practice of causing the total resistance of the
circuit extraneous to the generator to be equal to that of the generator almost
universally prevails, and by which the maximum effect is obtained, is very wasteful
of energy, for by thus arranging the resistances fifty per cent. of the energy is lost
in the machine itself, whereas if the exterior resistance is four times greater than
the machine the capacity of the machine to translate energy from one to the other
is lessened, but of what is translated, owing to the changed conditions, eighty per
cent. may be utilized. For this reason I so arrange the resistance of the main
conductors that they should be but one tenth of the total resistance of all the lamps,
and the resistance due to the generating machines is kept down by keeping in
multiple-arc a greater number of machines than is necessary to supply all the lights
which may happen to be in circuit at the time.
I claim as my Invention,
First. The combination with a sealed vacuum chamber made of a glass vessel of a
continuous incandescent conductor wound upon a bobbin of infusible material,
substantially as set forth.
Second. The method herein described of preparing metals and metallic conductors
for electric lamps or burners, consisting in freeing the metallic conductors of gases
in a vacuum, and then hermetically sealing the surrounding air tight transparent
case, substantially as specified.
Third. In an electric lamp, the combination with a sealed transparent vacuum
case of a bobbin of pyroinsulated wire wound upon an infusible substance,
substantially as specified.
Fourth. In combination with an electric light and the circuits thereof, two electro
magnets, one of which is caused to revolve, a governor operated by the speed, and a
circuit regulator controlled by the governor, whereby the uniformity of the current
passing to the light is maintained, substantially as set forth.
Fifth. In combination with an electric light, an adjustable circuit regulator
composed of the insulated springs connected with the circuit wires, a contact block
upon which said springs rest, and a governor lever to regulate the pressure of the
contact springs upon the contact block, substantially as set forth.
Sixth. The process of molding sticks of pulverulent material, consisting in filling
the mold with the material to be compressed, and then compressing the mass by
successive operations by means of a plunger and plunger sections, substantially as
described.
Seventh. The divided mold and block e in combination with the plunger a²
and plunger sections ³, substantially as and for the purposes set forth.
Eighth. The combination in a magneto electric machino of the helix of wire bo
and the wires e, wound and connected to the commutator blocks it as described, and
forming a parallel induction coil that occupies the space and revolves between tho
poles of the field magnet, substantially as set forth.
Ninth. The combination in a magneto electric machine of the magnetic cylinder,
composed of the helix 60 surrounded by the parallel induction coil e, and revolving
between the poles of the field magnet, the commutator i, springs d and d³, and
circuit connections, substantially as set forth.
Tenth. In a magneto electric machine, a parallel induction coil, the wires of which
are wound substantially as shown in Fig. 11, and commutator connections to the
wires, whereby the current is taken off from the parallel induction coil at two points
in opposite directions, substantially as set' forth.
'
Eleventh. The cylinder 63, of wood or similar material, with the iron heads
and intervening helix of wire 60 in combination with the disks of non-
conducting material, and the induction helix c wound lengthwise and into notches
in the edges of the insulating disks, substantially as set forth.
Twelfth. A polarized electro-magnet in the multiple arc circuit of the magneto
electric machine, for opening the circuit to the machine to which it is connected in
case of deragement of said machine,

page_text: Thirteenth. The thermo-electric piles, connected as set forth upon the condensing
pipes of an engine, in combination with the magneto electric machine, substantially
as set forth.
Fourteenth. The combination with the electric conductors M of metallic tubes
lined with hard rubber or similar non conducting substance, substantially as set
forth.
Fifteenth. The metallic tubes lined with non-conducting material, such as hard
rubber, in combination with metallic boxes B lined with similar material, and
uniting the tubes and the conductors passed through such tubes, substantially as set
forth.
Sixteenth. An induction bobbin nearly surrounded by the poles of the field
magnet, and the combination therewith of an abnormally large field magnet, which
shall be in proportion to the size of the pole-pieces, as described, for obtaining a
powerful electro-motive force in the wires of the revolving bobbin without great
loss of energy, as set forth.
In witness whereof, I have hereunto set my hand and seal, this Twenty fifth
dow of November
AD 1879
Witnesses,
S. L. GRIFFIN, of Menlo Park, N. J.
WM. CARMAN, of Menlo Park, N. J.
THOMAS ALVA EDISON. (L.S.)