We present a diagrammatic illustration of the Edison quadruplex, battery

key system, in Fig. 8, and refer the reader to the above or other

text-books if he desires to make a close study of its intricate

operations. Before finally dismissing the quadruplex, and for the

benefit of the inquiring reader who may vainly puzzle over the

intricacies of the circuits shown in Fig. 8, a hint as to an essential

difference between the neutral relay, as used in the duplex and as used

in the quadruplex, may be given. With the duplex, as we have seen, the

current on the main line is changed in strength only when both keys at

OPPOSITE stations are closed together, so that a current due to both

batteries flows over the main line. When a single message is sent from

one station to the other, or when both stations are sending messages

that do not conflict, only one battery or the other is connected to the

main line; but with the quadruplex, suppose one of the operators, in New

York for instance, is sending reversals of current to Chicago; we can

readily see how these changes in polarity will operate the polar relay

at the distant station, but why will they not also operate the neutral

relay at the distant station as well? This difficulty was solved by

dividing the battery at each station into two unequal parts, the smaller

battery being always in circuit with the pole-changer ready to have its

polarity reversed on the main line to operate the distant polar relay,

but the spring retracting the armature of the neutral relay is made so

stiff as to resist these weak currents. If, however, the transmitter is

operated at the same end, the entire battery is connected to the main

line, and the strength of this current is sufficient to operate the

neutral relay. Whether the part or all the battery is alternately

connected to or disconnected from the main line by the transmitter, the

current so varied in strength is subject to reversal of polarity by the

pole-changer; but the variations in strength have no effect upon the

distant polar relay, because that relay being responsive to changes

in polarity of a weak current is obviously responsive to corresponding

changes in polarity of a powerful current. With this distinction before

him, the reader will have no difficulty in following the circuits

of Fig. 8, bearing always in mind that by reason of the differential

winding of the polar and neutral relays, neither of the relays at one

station will respond to the home battery, and can only respond to the

distant battery--the polar relay responding when the polarity of the

current is reversed, whether the current be strong or weak, and the

neutral relay responding when the line-current is increased, regardless

of its polarity. It should be added that besides the system illustrated

in Fig. 8, which is known as the differential principle, the quadruplex

was also arranged to operate on the Wheatstone bridge principle; but

it is not deemed necessary to enter into its details. The underlying

phenomena were similar, the difference consisting largely in the

arrangement of the circuits and apparatus. [24]

[Footnote 24: Many of the illustrations in this article are

reproduced from American Telegraphy and Encyclopedia of the

Telegraph, by William Maver, Jr., by permission of Maver

Publishing Company, New York.]

Edison made another notable contribution to multiplex telegraphy

some years later in the Phonoplex. The name suggests the use of the

telephone, and such indeed is the case. The necessity for this invention

arose out of the problem of increasing the capacity of telegraph lines

employed in "through" and "way" service, such as upon railroads. In a

railroad system there are usually two terminal stations and a number of

way stations. There is naturally much intercommunication, which would

be greatly curtailed by a system having the capacity of only a single

message at a time. The duplexes above described could not be used on

a railroad telegraph system, because of the necessity of electrically

balancing the line, which, while entirely feasible on a through line,

would not be practicable between a number of intercommunicating points.

Edison's phonoplex normally doubled the capacity of telegraph lines,

whether employed on way business or through traffic, but in actual

practice made it possible to obtain more than double service. It has

been in practical use for many years on some of the leading railroads of

the United States.

The system is a combination of telegraphic apparatus and telephone

receiver, although in this case the latter instrument is not used in the

generally understood manner. It is well known that the diaphragm of a

telephone vibrates with the fluctuations of the current energizing the

magnet beneath it. If the make and break of the magnetizing current

be rapid, the vibrations being within the limits of the human ear, the

diaphragm will produce an audible sound; but if the make and break be as

slow as with ordinary Morse transmission, the diaphragm will be merely

flexed and return to its original form without producing a sound. If,

therefore, there be placed in the same circuit a regular telegraph relay

and a special telephone, an operator may, by manipulating a key, operate

the relay (and its sounder) without producing a sound in the telephone,

as the makes and breaks of the key are far below the limit of

audibility. But if through the same circuit, by means of another key

suitably connected there is sent the rapid changes in current from an

induction-coil, it will cause a series of loud clicks in the telephone,

corresponding to the signals transmitted; but this current is too weak

to affect the telegraph relay. It will be seen, therefore, that this

method of duplexing is practiced, not by varying the strength or

polarity, but by sending TWO KINDS OF CURRENT over the wire. Thus, two

sets of Morse signals can be transmitted by two operators over one

line at the same time without interfering with each other, and not only

between terminal offices, but also between a terminal office and any

intermediate office, or between two intermediate offices alone.

III

AUTOMATIC TELEGRAPHY

FROM the year 1848, when a Scotchman, Alexander Bain, first devised a

scheme for rapid telegraphy by automatic methods, down to the beginning

of the seventies, many other inventors had also applied themselves to

the solution of this difficult problem, with only indifferent success.

"Cheap telegraphy" being the slogan of the time, Edison became arduously

interested in the subject, and at the end of three years of hard work

produced an entirely successful system, a public test of which was made

on December 11, 1873 when about twelve thousand (12,000) words

were transmitted over a single wire from Washington to New York. in

twenty-two and one-half minutes. Edison's system was commercially

exploited for several years by the Automatic Telegraph Company, as

related in the preceding narrative.

As a premise to an explanation of the principles involved it should be

noted that the transmission of telegraph messages by hand at a rate of

fifty words per minute is considered a good average speed; hence, the

availability of a telegraph line, as thus operated, is limited to this

capacity except as it may be multiplied by two with the use of

the duplex, or by four, with the quadruplex. Increased rapidity of

transmission may, however, be accomplished by automatic methods, by

means of which, through the employment of suitable devices, messages may

be stamped in or upon a paper tape, transmitted through automatically

acting instruments, and be received at distant points in visible

characters, upon a similar tape, at a rate twenty or more times

greater--a speed far beyond the possibilities of the human hand to

transmit or the ear to receive.

In Edison's system of automatic telegraphy a paper tape was perforated

with a series of round holes, so arranged and spaced as to represent

Morse characters, forming the words of the message to be transmitted.

This was done in a special machine of Edison's invention, called a

perforator, consisting of a series of punches operated by a bank of

keys--typewriter fashion. The paper tape passed over a cylinder, and

was kept in regular motion so as to receive the perforations in proper

sequence.

The perforated tape was then placed in the transmitting instrument,

the essential parts of which were a metallic drum and a projecting arm

carrying two small wheels, which, by means of a spring, were maintained

in constant pressure on the drum. The wheels and drum were electrically

connected in the line over which the message was to be sent. current

being supplied by batteries in the ordinary manner.

When the transmitting instrument was in operation, the perforated tape

was passed over the drum in continuous, progressive motion. Thus, the

paper passed between the drum and the two small wheels, and, as dry

paper is a non-conductor, current was prevented from passing until a

perforation was reached. As the paper passed along, the wheels dropped

into the perforations, making momentary contacts with the drum beneath

and causing momentary impulses of current to be transmitted over the

line in the same way that they would be produced by the manipulation

of the telegraph key, but with much greater rapidity. The perforations

being so arranged as to regulate the length of the contact, the result

would be the transmission of long and short impulses corresponding with

the dots and dashes of the Morse alphabet.

The receiving instrument at the other end of the line was constructed

upon much the same general lines as the transmitter, consisting of a

metallic drum and reels for the paper tape. Instead of the two small

contact wheels, however, a projecting arm carried an iron pin or stylus,

so arranged that its point would normally impinge upon the periphery of

the drum. The iron pin and the drum were respectively connected so as to

be in circuit with the transmission line and batteries. As the principle

involved in the receiving operation was electrochemical decomposition,

the paper tape upon which the incoming message was to be received was

moistened with a chemical solution readily decomposable by the electric

current. This paper, while still in a damp condition, was passed

between the drum and stylus in continuous, progressive motion. When an

electrical impulse came over the line from the transmitting end, current

passed through the moistened paper from the iron pin, causing chemical

decomposition, by reason of which the iron would be attacked and would

mark a line on the paper. Such a line would be long or short, according

to the duration of the electric impulse. Inasmuch as a succession of

such impulses coming over the line owed their origin to the perforations

in the transmitting tape, it followed that the resulting marks upon the

receiving tape would correspond thereto in their respective lengths.

Hence, the transmitted message was received on the tape in visible dots

and dashes representing characters of the Morse alphabet.

The system will, perhaps, be better understood by reference to the

following diagrammatic sketch of its general principles:

Some idea of the rapidity of automatic telegraphy may be obtained when

we consider the fact that with the use of Edison's system in the early

seventies it was common practice to transmit and receive from three to

four thousand words a minute over a single line between New York and

Philadelphia. This system was exploited through the use of a moderately

paid clerical force.

In practice, there was employed such a number of perforating machines

as the exigencies of business demanded. Each machine was operated by

a clerk, who translated the message into telegraphic characters and

prepared the transmitting tape by punching the necessary perforations

therein. An expert clerk could perforate such a tape at the rate of

fifty to sixty words per minute. At the receiving end the tape was taken

by other clerks who translated the Morse characters into ordinary words,

which were written on message blanks for delivery to persons for whom

the messages were intended.

This latter operation--"copying." as it was called--was not consistent

with truly economical business practice. Edison therefore undertook the

task of devising an improved system whereby the message when received

would not require translation and rewriting, but would automatically

appear on the tape in plain letters and words, ready for instant

delivery.

The result was his automatic Roman letter system, the basis for which

included the above-named general principles of perforated transmission

tape and electrochemical decomposition. Instead of punching Morse

characters in the transmission tape however, it was perforated with

a series of small round holes forming Roman letters. The verticals

of these letters were originally five holes high. The transmitting

instrument had five small wheels or rollers, instead of two, for making

contacts through the perforations and causing short electric impulses

to pass over the lines. At first five lines were used to carry these

impulses to the receiving instrument, where there were five iron pins

impinging on the drum. By means of these pins the chemically prepared

tape was marked with dots corresponding to the impulses as received,

leaving upon it a legible record of the letters and words transmitted.

For purposes of economy in investment and maintenance, Edison devised

subsequently a plan by which the number of conducting lines was reduced

to two, instead of five. The verticals of the letters were perforated

only four holes high, and the four rollers were arranged in pairs, one

pair being slightly in advance of the other. There were, of course,

only four pins at the receiving instrument. Two were of iron and two of

tellurium, it being the gist of Edison's plan to effect the marking

of the chemical paper by one metal with a positive current, and by the

other metal with a negative current. In the following diagram, which

shows the theory of this arrangement, it will be seen that both the

transmitting rollers and the receiving pins are arranged in pairs,

one pair in each case being slightly in advance of the other. Of these

receiving pins, one pair--1 and 3--are of iron, and the other pair--2

and 4--of tellurium. Pins 1-2 and 3-4 are electrically connected

together in other pairs, and then each of these pairs is connected with

one of the main lines that run respectively to the middle of two groups

of batteries at the transmitting end. The terminals of these groups of

batteries are connected respectively to the four rollers which impinge

upon the transmitting drum, the negatives being connected to 5 and 7,

and the positives to 6 and 8, as denoted by the letters N and P. The

transmitting and receiving drums are respectively connected to earth.

In operation the perforated tape is placed on the transmission drum, and

the chemically prepared tape on the receiving drum. As the perforated

tape passes over the transmission drum the advanced rollers 6 or 8

first close the circuit through the perforations, and a positive current

passes from the batteries through the drum and down to the ground;

thence through the earth at the receiving end up to the other drum and

back to the batteries via the tellurium pins 2 or 4 and the line wire.

With this positive current the tellurium pins make marks upon the

paper tape, but the iron pins make no mark. In the merest fraction of a

second, as the perforated paper continues to pass over the transmission

drum, the rollers 5 or 7 close the circuit through other perforations

and t e current passes in the opposite direction, over the line wire,

through pins 1 or 3, and returns through the earth. In this case the

iron pins mark the paper tape, but the tellurium pins make no mark. It

will be obvious, therefore, that as the rollers are set so as to allow

of currents of opposite polarity to be alternately and rapidly sent

by means of the perforations, the marks upon the tape at the receiving

station will occupy their proper relative positions, and the aggregate

result will be letters corresponding to those perforated in the

transmission tape.

Edison subsequently made still further improvements in this direction,

by which he reduced the number of conducting wires to one, but the

principles involved were analogous to the one just described.

This Roman letter system was in use for several years on lines between

New York, Philadelphia, and Washington, and was so efficient that a

speed of three thousand words a minute was attained on the line between

the two first-named cities.

Inasmuch as there were several proposed systems of rapid automatic

telegraphy in existence at the time Edison entered the field, but none

of them in practical commercial use, it becomes a matter of interest to

inquire wherein they were deficient, and what constituted the elements

of Edison's success.

The chief difficulties in the transmission of Morse characters had been

two in number, the most serious of which was that on the receiving tape

the characters would be prolonged and run into one another, forming a

draggled line and thus rendering the message unintelligible. This arose

from the fact that, on account of the rapid succession of the electric

impulses, there was not sufficient time between them for the electric

action to cease entirely. Consequently the line could not clear itself,

and became surcharged, as it were; the effect being an attenuated

prolongation of each impulse as manifested in a weaker continuation of

the mark on the tape, thus making the whole message indistinct. These

secondary marks were called "tailings."

For many years electricians had tried in vain to overcome this

difficulty. Edison devoted a great deal of thought and energy to the

question, in the course of which he experimented through one hundred

and twenty consecutive nights, in the year 1873, on the line between

New York and Washington. His solution of the problem was simple but

effectual. It involved the principle of inductive compensation. In

a shunt circuit with the receiving instrument he introduced

electromagnets. The pulsations of current passed through the helices of

these magnets, producing an augmented marking effect upon the receiving

tape, but upon the breaking of the current, the magnet, in discharging

itself of the induced magnetism, would set up momentarily a

counter-current of opposite polarity. This neutralized the "tailing"

effect by clearing the line between pulsations, thus allowing the

telegraphic characters to be clearly and distinctly outlined upon the

tape. Further elaboration of this method was made later by the addition

of rheostats, condensers, and local opposition batteries on long lines.

The other difficulty above referred to was one that had also occupied

considerable thought and attention of many workers in the field, and

related to the perforating of the dash in the transmission tape. It

involved mechanical complications that seemed to be insurmountable, and

up to the time Edison invented his perforating machine no really good

method was available. He abandoned the attempt to cut dashes as such, in

the paper tape, but instead punched three round holes so arranged as

to form a triangle. A concrete example is presented in the illustration

below, which shows a piece of tape with perforations representing the

word "same."

The philosophy of this will be at once perceived when it is remembered

that the two little wheels running upon the drum of the transmitting

instrument were situated side by side, corresponding in distance to the

two rows of holes. When a triangle of three holes, intended to form the

dash, reached the wheels, one of them dropped into a lower hole. Before

it could get out, the other wheel dropped into the hole at the apex of

the triangle, thus continuing the connection, which was still further

prolonged by the first wheel dropping into the third hole. Thus, an

extended contact was made, which, by transmitting a long impulse,

resulted in the marking of a dash upon the receiving tape.

This method was in successful commercial use for some time in the early

seventies, giving a speed of from three to four thousand words a minute

over a single line, but later on was superseded by Edison's Roman letter

system, above referred to.

The subject of automatic telegraphy received a vast amount of attention

from inventors at the time it was in vogue. None was more earnest

or indefatigable than Edison, who, during the progress of his

investigations, took out thirty-eight patents on various inventions

relating thereto, some of them covering chemical solutions for the

receiving paper. This of itself was a subject of much importance and

a vast amount of research and labor was expended upon it. In the

laboratory note-books there are recorded thousands of experiments

showing that Edison's investigations not only included an enormous

number of chemical salts and compounds, but also an exhaustive variety

of plants, flowers, roots, herbs, and barks.

It seems inexplicable at first view that a system of telegraphy

sufficiently rapid and economical to be practically available for

important business correspondence should have fallen into disuse. This,

however, is made clear--so far as concerns Edison's invention at any

rate--in Chapter VIII of the preceding narrative.

IV. WIRELESS TELEGRAPHY

ALTHOUGH Mr. Edison has taken no active part in the development of

the more modern wireless telegraphy, and his name has not occurred in

connection therewith, the underlying phenomena had been noted by him

many years in advance of the art, as will presently be explained. The

authors believe that this explanation will reveal a status of Edison in

relation to the subject that has thus far been unknown to the public.

While the term "wireless telegraphy," as now applied to the modern

method of electrical communication between distant points without

intervening conductors, is self-explanatory, it was also applicable,

strictly speaking, to the previous art of telegraphing to and from

moving trains, and between points not greatly remote from each other,

and not connected together with wires.

The latter system (described in Chapter XXIII and in a succeeding

article of this Appendix) was based upon the phenomena of

electromagnetic or electrostatic induction between conductors separated

by more or less space, whereby electric impulses of relatively low

potential and low frequency set up in. one conductor were transmitted

inductively across the air to another conductor, and there received

through the medium of appropriate instruments connected therewith.

As distinguished from this system, however, modern wireless

telegraphy--so called--has its basis in the utilization of electric

or ether waves in free space, such waves being set up by electric

oscillations, or surgings, of comparatively high potential and high

frequency, produced by the operation of suitable electrical apparatus.

Broadly speaking, these oscillations arise from disruptive discharges of

an induction coil, or other form of oscillator, across an air-gap, and

their character is controlled by the manipulation of a special type of

circuit-breaking key, by means of which long and short discharges are

produced. The electric or etheric waves thereby set up are detected

and received by another special form of apparatus more or less distant,

without any intervening wires or conductors.

In November, 1875, Edison, while experimenting in his Newark laboratory,

discovered a new manifestation of electricity through mysterious sparks

which could be produced under conditions unknown up to that time.

Recognizing at once the absolutely unique character of the phenomena, he

continued his investigations enthusiastically over two mouths, finally

arriving at a correct conclusion as to the oscillatory nature of the

hitherto unknown manifestations. Strange to say, however, the true

import and practical applicability of these phenomena did not occur to

his mind. Indeed, it was not until more than TWELVE YEARS AFTERWARD, in

1887, upon the publication of the notable work of Prof. H. Hertz proving

the existence of electric waves in free space, that Edison realized the

fact that the fundamental principle of aerial telegraphy had been within

his grasp in the winter of 1875; for although the work of Hertz was more

profound and mathematical than that of Edison, the principle involved

and the phenomena observed were practically identical--in fact, it may

be remarked that some of the methods and experimental apparatus were

quite similar, especially the "dark box" with micrometer adjustment,

used by both in observing the spark. [25]

[Footnote 25: During the period in which Edison exhibited

his lighting system at the Paris Exposition in 1881, his

representative, Mr. Charles Batchelor, repeated Edison's

remarkable experiments of the winter of 1875 for the benefit

of a great number of European savants, using with other

apparatus the original "dark box" with micrometer

adjustment.]

There is not the slightest intention on the part of the authors to

detract in the least degree from the brilliant work of Hertz, but, on

the contrary, to ascribe to him the honor that is his due in having

given mathematical direction and certainty to so important a discovery.

The adaptation of the principles thus elucidated and the subsequent

development of the present wonderful art by Marconi, Branly, Lodge,

Slaby, and others are now too well known to call for further remark at

this place.

Strange to say, that although Edison's early experiments in "etheric

force" called forth extensive comment and discussion in the public

prints of the period, they seemed to have been generally overlooked

when the work of Hertz was published. At a meeting of the Institution of

Electrical Engineers, held in London on May 16, 1889, at which there

was a discussion on the celebrated paper of Prof. (Sir) Oliver Lodge on

"Lightning Conductors," however; the chairman, Sir William Thomson (Lord

Kelvin), made the following remarks:

"We all know how Faraday made himself a cage six feet in diameter, hung

it up in mid-air in the theatre of the Royal Institution, went into it,

and, as he said, lived in it and made experiments. It was a cage with

tin-foil hanging all round it; it was not a complete metallic enclosing

shell. Faraday had a powerful machine working in the neighborhood,

giving all varieties of gradual working-up and discharges by 'impulsive

rush'; and whether it was a sudden discharge of ordinary insulated

conductors, or of Leyden jars in the neighborhood outside the cage, or

electrification and discharge of the cage itself, he saw no effects on

his most delicate gold-leaf electroscopes in the interior. His attention

was not directed to look for Hertz sparks, or probably he might have

found them in the interior. Edison seems to have noticed something of

the kind in what he called the etheric force. His name 'etheric' may,

thirteen years ago, have seemed to many people absurd. But now we are

all beginning to call these inductive phenomena 'etheric.'"

With these preliminary observations, let us now glance briefly at

Edison's laboratory experiments, of which mention has been made.

Oh the first manifestation of the unusual phenomena in November, 1875,

Edison's keenness of perception led him at once to believe that he had

discovered a new force. Indeed, the earliest entry of this discovery in

the laboratory note-book bore that caption. After a few days of further

experiment and observation, however, he changed it to "Etheric Force,"

and the further records thereof (all in Mr. Batchelor's handwriting)

were under that heading.

The publication of Edison's discovery created considerable attention at

the time, calling forth a storm of general ridicule and incredulity.

But a few scientific men of the period, whose experimental methods were

careful and exact, corroborated his deductions after obtaining similar

phenomena by repeating his experiments with intelligent precision. Among

these was the late Dr. George M. Beard, a noted physicist, who entered

enthusiastically into the investigation, and, in addition to a great

deal of independent experiment, spent much time with Edison at his

laboratory. Doctor Beard wrote a treatise of some length on the subject,

in which he concurred with Edison's deduction that the phenomena

were the manifestation of oscillations, or rapidly reversing waves

of electricity, which did not respond to the usual tests. Edison

had observed the tendency of this force to diffuse itself in various

directions through the air and through matter, hence the name "Etheric"

that he had provisionally applied to it.

Edison's laboratory notes on this striking investigation are fascinating

and voluminous, but cannot be reproduced in full for lack of space.

In view of the later practical application of the principles involved,

however, the reader will probably be interested in perusing a few

extracts therefrom as illustrated by facsimiles of the original sketches

from the laboratory note-book.

As the full significance of the experiments shown by these extracts

may not be apparent to a lay reader, it may be stated by way of premise

that, ordinarily, a current only follows a closed circuit. An electric

bell or electric light is a familiar instance of this rule. There is in

each case an open (wire) circuit which is closed by pressing the button

or turning the switch, thus making a complete and uninterrupted path in

which the current may travel and do its work. Until the time of Edison's

investigations of 1875, now under consideration, electricity had never

been known to manifest itself except through a closed circuit. But, as

the reader will see from the following excerpts, Edison discovered a

hitherto unknown phenomenon--namely, that under certain conditions the

rule would be reversed and electricity would pass through space and

through matter entirely unconnected with its point of origin. In other

words, he had found the forerunner of wireless telegraphy. Had he then

realized the full import of his discovery, all he needed was to increase

the strength of the waves and to provide a very sensitive detector, like

the coherer, in order to have anticipated the principal developments

that came many years afterward. With these explanatory observations, we

will now turn to the excerpts referred to, which are as follows:

"November 22, 1875. New Force.--In experimenting with a vibrator magnet

consisting of a bar of Stubb's steel fastened at one end and made to

vibrate by means of a magnet, we noticed a spark coming from the cores

of the magnet. This we have noticed often in relays, in stock-printers,

when there were a little iron filings between the armature and core,

and more often in our new electric pen, and we have always come to the

conclusion that it was caused by strong induction. But when we noticed

it on this vibrator it seemed so strong that it struck us forcibly there

might be something more than induction. We now found that if we touched

any metallic part of the vibrator or magnet we got the spark. The larger

the body of iron touched to the vibrator the larger the spark. We now

connected a wire to X, the end of the vibrating rod, and we found we

could get a spark from it by touching a piece of iron to it, and one of

the most curious phenomena is that if you turn the wire around on itself

and let the point of the wire touch any other portion of itself you

get a spark. By connecting X to the gas-pipe we drew sparks from the

gas-pipes in any part of the room by drawing an iron wire over the brass

jet of the cock. This is simply wonderful, and a good proof that the

cause of the spark is a TRUE UNKNOWN FORCE."

"November 23, 1815. New Force.--The following very curious result was

obtained with it. The vibrator shown in Fig. 1 and battery were placed

on insulated stands; and a wire connected to X (tried both copper and

iron) carried over to the stove about twenty feet distant. When the end

of the wire was rubbed on the stove it gave out splendid sparks. When

permanently connected to the stove, sparks could be drawn from the stove

by a piece of wire held in the hand. The point X of vibrator was now

connected to the gas-pipe and still the sparks could be drawn from the

stove."

. . . . . . . . .

"Put a coil of wire over the end of rod X and passed the ends of spool

through galvanometer without affecting it in any way. Tried a 6-ohm

spool add a 200-ohm. We now tried all the metals, touching each one in

turn to the point X." [Here follows a list of metals and the character

of spark obtained with each.]

. . . . . . . . .

"By increasing the battery from eight to twelve cells we get a spark

when the vibrating magnet is shunted with 3 ohms. Cannot taste the least

shock at B, yet between carbon points the spark is very vivid. As will

be seen, X has no connection with anything. With a glass rod four feet

long, well rubbed with a piece of silk over a hot stove, with a piece

of battery carbon secured to one end, we received vivid sparks into the

carbon when the other end was held in the hand with the handkerchief,

yet the galvanometer, chemical paper, the sense of shock in the tongue,

and a gold-leaf electroscope which would diverge at two feet from a

half-inch spark plate-glass machine were not affected in the least by

it.

"A piece of coal held to the wire showed faint sparks.

"We had a box made thus: whereby two points could be brought together

within a dark box provided with an eyepiece. The points were iron, and

we found the sparks were very irregular. After testing some time two

lead-pencils found more regular and very much more vivid. We then

substituted the graphite points instead of iron." [26]

[Footnote 26: The dark box had micrometer screws for

delicate adjustment of the carbon points, and was thereafter

largely used in this series of investigations for better

study of the spark. When Mr. Edison's experiments were

repeated by Mr. Batchelor, who represented him at the Paris

Exposition of 1881, the dark box was employed for a similar

purpose.]

. . . . . . . . .

After recording a considerable number of other experiments, the

laboratory notes go on to state:

"November 30, 1875. Etheric Force.--We found the addition of battery to

the Stubb's wire vibrator greatly increased the volume of spark. Several

persons could obtain sparks from the gas-pipes at once, each spark being

equal in volume and brilliancy to the spark drawn by a single person....

Edison now grasped the (gas) pipe, and with the other hand holding a

piece of metal, he touched several other metallic substances, obtained

sparks, showing that the force passed through his body."

. . . . . . . . .

"December 3, 1875. Etheric Force.--Charley Edison hung to the gas-pipe

with feet above the floor, and with a knife got a spark from the pipe he

was hanging on. We now took the wire from the vibrator in one hand

and stood on a block of paraffin eighteen inches square and six inches

thick; holding a knife in the other hand, we drew sparks from the

stove-pipe. We now tried the crucial test of passing the etheric current

through the sciatic nerve of a frog just killed. Previous to trying, we

tested its sensibility by the current from a single Bunsen cell. We

put in resistance up to 500,000 ohms, and the twitching was still

perceptible. We tried the induced current from our induction coil having

one cell on primary,, the spark jumping about one-fiftieth of an inch,

the terminal of the secondary connected to the frog and it straightened

out with violence. We arranged frog's legs to pass etheric force

through. We placed legs on an inverted beaker, and held the two ends

of the wires on glass rods eight inches long. On connecting one to the

sciatic nerve and the other to the fleshy part of the leg no movement

could be discerned, although brilliant sparks could be obtained on the

graphite points when the frog was in circuit. Doctor Beard was present

when this was tried."

. . . . . . . . .

"December 5, 1875. Etheric Force.--Three persons grasping hands and

standing upon blocks of paraffin twelve inches square and six thick drew

sparks from the adjoining stove when another person touched the sounder

with any piece of metal.... A galvanoscopic frog giving contractions

with one cell through two water rheostats was then placed in circuit.

When the wires from the vibrator and the gas-pipe were connected, slight

contractions were noted, sometimes very plain and marked, showing the

apparent presence of electricity, which from the high insulation seemed

improbable. Doctor Beard, who was present, inferred from the way the

leg contracted that it moved on both opening and closing the circuit.

To test this we disconnected the wire between the frog and battery, and

placed, instead of a vibrating sounder, a simple Morse key and a sounder

taking the 'etheric' from armature. The spark was now tested in dark box

and found to be very strong. It was then connected to the nerves of the

frog, BUT NO MOVEMENT OF ANY KIND COULD BE DETECTED UPON WORKING THE

KEY, although the brilliancy and power of the spark were undiminished.

The thought then occurred to Edison that the movement of the frog was

due to mechanical vibrations from the vibrator (which gives probably two

hundred and fifty vibrations per second), passing through the wires

and irritating the sensitive nerves of the frog. Upon disconnecting

the battery wires and holding a tuning-fork giving three hundred

and twenty-six vibrations per second to the base of the sounder, the

vibrations over the wire made the frog contract nearly every time....

The contraction of the frog's legs may with considerable safety be said

to be caused by these mechanical vibrations being transmitted through

the conducting wires."

Edison thought that the longitudinal vibrations caused by the sounder

produced a more marked effect, and proceeded to try out his theory. The

very next entry in the laboratory note-book bears the same date as the

above (December 5, 1875), and is entitled "Longitudinal Vibrations," and

reads as follows:

"We took a long iron wire one-sixteenth of an inch in diameter and

rubbed it lengthways with a piece of leather with resin on for about

three feet, backward and forward. About ten feet away we applied the

wire to the back of the neck and it gives a horrible sensation, showing

the vibrations conducted through the wire."

. . . . . . . . .

The following experiment illustrates notably the movement of the

electric waves through free space:

"December 26, 1875. Etheric Force.--An experiment tried to-night gives a

curious result. A is a vibrator, B, C, D, E are sheets of tin-foil hung

on insulating stands. The sheets are about twelve by eight inches. B and

C are twenty-six inches apart, C and D forty-eight inches and D and E

twenty-six inches. B is connected to the vibrator and E to point in

dark box, the other point to ground. We received sparks at intervals,

although insulated by such space."

With the above our extracts must close, although we have given but a few

of the interesting experiments tried at the time. It will be noticed,

however, that these records show much progression in a little over a

month. Just after the item last above extracted, the Edison shop became

greatly rushed on telegraphic inventions, and not many months afterward

came the removal to Menlo Park; hence the etheric-force investigations

were side-tracked for other matters deemed to be more important at that

time.

Doctor Beard in his previously mentioned treatise refers, on page 27, to

the views of others who have repeated Edison's experiments and observed

the phenomena, and in a foot-note says:

"Professor Houston, of Philadelphia, among others, has repeated some of

these physical experiments, has adopted in full and after but a partial

study of the subject, the hypothesis of rapidly reversed electricity

as suggested in my letter to the Tribune of December 8th, and further

claims priority of discovery, because he observed the spark of this when

experimenting with a Ruhmkorff coil four years ago. To this claim, if

it be seriously entertained, the obvious reply is that thousands of

persons, probably, had seen this spark before it was DISCOVERED by Mr.

Edison; it had been seen by Professor Nipher, who supposed, and still

supposes, it is the spark of the extra current; it has been seen by

my friend, Prof. J. E. Smith, who assumed, as he tells me, without

examination, that it was inductive electricity breaking through bad

insulation; it had been seen, as has been stated, by Mr. Edison many

times before he thought it worthy of study, it was undoubtedly seen by

Professor Houston, who, like so many others, failed to even suspect

its meaning and thus missed an important discovery. The honor of a

scientific discovery belongs, not to him who first sees a thing, but

to him who first sees it with expert eyes; not to him even who drops

an original suggestion, but to him who first makes, that suggestion

fruitful of results. If to see with the eyes a phenomenon is to discover

the law of which that phenomenon is a part, then every schoolboy who,

before the time of Newton, ever saw an apple fall, was a discoverer of

the law of gravitation...."

Edison took out only one patent on long-distance telegraphy without

wires. While the principle involved therein (induction) was not

precisely analogous to the above, or to the present system of wireless

telegraphy, it was a step forward in the progress of the art. The

application was filed May 23, 1885, at the time he was working on

induction telegraphy (two years before the publication of the work of

Hertz), but the patent (No. 465,971) was not issued until December

29, 1891. In 1903 it was purchased from him by the Marconi Wireless

Telegraph Company. Edison has always had a great admiration for Marconi

and his work, and a warm friendship exists between the two men. During

the formative period of the Marconi Company attempts were made to

influence Edison to sell this patent to an opposing concern, but his

regard for Marconi and belief in the fundamental nature of his work were

so strong that he refused flatly, because in the hands of an enemy the

patent might be used inimically to Marconi's interests.

Edison's ideas, as expressed in the specifications of this patent, show

very clearly the close analogy of his system to that now in vogue.

As they were filed in the Patent Office several years before the

possibility of wireless telegraphy was suspected, it will undoubtedly be

of interest to give the following extract therefrom:

"I have discovered that if sufficient elevation be obtained to overcome

the curvature of the earth's surface and to reduce to the minimum the

earth's absorption, electric telegraphing or signalling between

distant points can be carried on by induction without the use of wires

connecting such distant points. This discovery is especially applicable

to telegraphing across bodies of water, thus avoiding the use of

submarine cables, or for communicating between vessels at sea, or

between vessels at sea and points on land, but it is also applicable

to electric communication between distant points on land, it being

necessary, however, on land (with the exception of communication over

open prairie) to increase the elevation in order to reduce to the

minimum the induction-absorbing effect of houses, trees, and elevations

in the land itself. At sea from an elevation of one hundred feet I can

communicate electrically a great distance, and since this elevation

or one sufficiently high can be had by utilizing the masts of ships,

signals can be sent and received between ships separated a considerable

distance, and by repeating the signals from ship to ship communication

can be established between points at any distance apart or across the

largest seas and even oceans. The collision of ships in fogs can be

prevented by this character of signalling, by the use of which, also,

the safety of a ship in approaching a dangerous coast in foggy weather

can be assured. In communicating between points on land, poles of great

height can be used, or captive balloons. At these elevated points,

whether upon the masts of ships, upon poles or balloons, condensing

surfaces of metal or other conductor of electricity are located. Each

condensing surface is connected with earth by an electrical conducting

wire. On land this earth connection would be one of usual character in

telegraphy. At sea the wire would run to one or more metal plates on the

bottom of the vessel, where the earth connection would be made with the

water. The high-resistance secondary circuit of an induction coil is

located in circuit between the condensing surface and the ground. The

primary circuit of the induction coil includes a battery and a device

for transmitting signals, which may be a revolving circuit-breaker

operated continually by a motor of any suitable kind, either electrical

or mechanical, and a key normally short-circuiting the circuit-breaker

or secondary coil. For receiving signals I locate in said circuit

between the condensing surface and the ground a diaphragm sounder, which

is preferably one of my electromotograph telephone receivers. The key

normally short-circuiting the revolving circuit-breaker, no impulses are

produced in the induction coil until the key is depressed, when a large

number of impulses are produced in the primary, and by means of the

secondary corresponding impulses or variations in tension are produced

at the elevated condensing surface, producing thereat electrostatic

impulses. These electrostatic impulses are transmitted inductively

to the elevated condensing surface at the distant point, and are made

audible by the electromotograph connected in the ground circuit with

such distant condensing surface."

The accompanying illustrations are reduced facsimiles of the drawings

attached to the above patent, No. 465,971.

V. THE ELECTROMOTOGRAPH

IN solving a problem that at the time was thought to be insurmountable,

and in the adaptability of its principles to the successful overcoming

of apparently insuperable difficulties subsequently arising in other

lines of work, this invention is one of the most remarkable of the many

that Edison has made in his long career as an inventor.

The object primarily sought to be accomplished was the repeating of

telegraphic signals from a distance without the aid of a galvanometer

or an electromagnetic relay, to overcome the claims of the Page patent

referred to in the preceding narrative. This object was achieved in the

device described in Edison's basic patent No. 158,787, issued January

19, 1875, by the substitution of friction and anti-friction for the

presence and absence of magnetism in a regulation relay.

It may be observed, parenthetically, for the benefit of the lay

reader, that in telegraphy the device known as the relay is a receiving

instrument containing an electromagnet adapted to respond to the weak

line-current. Its armature moves in accordance with electrical impulses,

or signals, transmitted from a distance, and, in so responding, operates

mechanically to alternately close and open a separate local circuit

in which there is a sounder and a powerful battery. When used for true

relaying purposes the signals received from a distance are in turn

repeated over the next section of the line, the powerful local battery

furnishing current for this purpose. As this causes a loud repetition

of the original signals, it will be seen that relaying is an economic

method of extending a telegraph circuit beyond the natural limits of its

battery power.

At the time of Edison's invention, as related in Chapter IX of the

preceding narrative, there existed no other known method than the one

just described for the repetition of transmitted signals, thus limiting

the application of telegraphy to the pleasure of those who might own any

patent controlling the relay, except on simple circuits where a single

battery was sufficient. Edison's previous discovery of differential

friction of surfaces through electrochemical decomposition was now

adapted by him to produce motion at the end of a circuit without

the intervention of an electromagnet. In other words, he invented a

telegraph instrument having a vibrator controlled by electrochemical

decomposition, to take the place of a vibrating armature operated by an

electromagnet, and thus opened an entirely new and unsuspected avenue in

the art.

Edison's electromotograph comprised an ingeniously arranged apparatus in

which two surfaces, normally in contact with each other, were caused

to alternately adhere by friction or slip by reason of electrochemical

decomposition. One of these surfaces consisted of a small drum or

cylinder of chalk, which was kept in a moistened condition with a

suitable chemical solution, and adapted to revolve continuously by

clockwork. The other surface consisted of a small pad which rested with

frictional pressure on the periphery of the drum. This pad was carried

on the end of a vibrating arm whose lateral movement was limited between

two adjustable points. Normally, the frictional pressure between the

drum and pad would carry the latter with the former as it revolved, but

if the friction were removed a spring on the end of the vibrator arm

would draw it back to its starting-place.

In practice, the chalk drum was electrically connected with one pole of

an incoming telegraph circuit, and the vibrating arm and pad with the

other pole. When the drum rotated, the friction of the pad carried the

vibrating arm forward, but an electrical impulse coming over the line

would decompose the chemical solution with which the drum was moistened,

causing an effect similar to lubrication, and thus allowing the pad to

slip backward freely in response to the pull of its retractile spring.

The frictional movements of the pad with the drum were comparatively

long or short, and corresponded with the length of the impulses sent in

over the line. Thus, the transmission of Morse dots and dashes by the

distant operator resulted in movements of corresponding length by the

frictional pad and vibrating arm.

This brings us to the gist of the ingenious way in which Edison

substituted the action of electrochemical decomposition for that of the

electromagnet to operate a relay. The actual relaying was accomplished

through the medium of two contacts making connection with the local

or relay circuit. One of these contacts was fixed, while the other was

carried by the vibrating arm; and, as the latter made its forward and

backward movements, these contacts were alternately brought together or

separated, thus throwing in and out of circuit the battery and sounder

in the local circuit and causing a repetition of the incoming signals.

The other side of the local circuit was permanently connected to an

insulated block on the vibrator. This device not only worked with great

rapidity, but was extremely sensitive, and would respond to currents

too weak to affect the most delicate electromagnetic relay. It should

be stated that Edison did not confine himself to the working of the

electromotograph by the slipping of surfaces through the action of

incoming current, but by varying the character of the surfaces in

contact the frictional effect might be intensified by the electrical

current. In such a case the movements would be the reverse of

those above indicated, but the end sought--namely, the relaying of

messages--would be attained with the same certainty.

While the principal object of this invention was to accomplish the

repetition of signals without the aid of an electromagnetic relay, the

instrument devised by Edison was capable of use as a recorder also, by

employing a small wheel inked by a fountain wheel and attached to the

vibrating arm through suitable mechanism. By means of this adjunct the

dashes and dots of the transmitted impulses could be recorded upon a

paper ribbon passing continuously over the drum.

The electromotograph is shown diagrammatically in Figs. 1 and 2, in plan

and vertical section respectively. The reference letters in each case

indicate identical parts: A being the chalk drum, B the paper tape, C

the auxiliary cylinder, D the vibrating arm, E the frictional pad, F the

spring, G and H the two contacts, I and J the two wires leading to local

circuit, K a battery, and L an ordinary telegraph key. The two last

named, K and L, are shown to make the sketch complete but in practice

would be at the transmitting end, which might be hundreds of miles

away. It will be understood, of course, that the electromotograph is a

receiving and relaying instrument.

Another notable use of the electromotograph principle was in its

adaptation to the receiver in Edison's loud-speaking telephone, on which

United States Patent No. 221,957 was issued November 25, 1879. A chalk

cylinder moistened with a chemical solution was revolved by hand or

a small motor. Resting on the cylinder was a palladium-faced pen or

spring, which was attached to a mica diaphragm in a resonator. The

current passed from the main line through the pen to the chalk and to

the battery. The sound-waves impinging upon the distant transmitter

varied the resistance of the carbon button therein, thus causing

corresponding variations in the strength of the battery current. These

variations, passing through the chalk cylinder produced more or less

electrochemical decomposition, which in turn caused differences of

adhesion between the pen and cylinder and hence gave rise to mechanical

vibrations of the diaphragm by reason of which the speaker's words were

reproduced. Telephones so operated repeated speaking and singing in

very loud tones. In one instance, spoken words and the singing of songs

originating at a distance were heard perfectly by an audience of over

five thousand people.

The loud-speaking telephone is shown in section, diagrammatically,

in the sketch (Fig. 3), in which A is the chalk cylinder mounted on

a shaft, B. The palladium-faced pen or spring, C, is connected to

diaphragm D. The instrument in its commercial form is shown in Fig. 4.

VI. THE TELEPHONE

ON April 27, 1877, Edison filed in the United States Patent Office an

application for a patent on a telephone, and on May 3, 1892, more

than fifteen years afterward, Patent No. 474,230 was granted thereon.

Numerous other patents have been issued to him for improvements in

telephones, but the one above specified may be considered as the

most important of them, since it is the one that first discloses the

principle of the carbon transmitter.

This patent embodies but two claims, which are as follows:

"1. In a speaking-telegraph transmitter, the combination of a metallic

diaphragm and disk of plumbago or equivalent material, the contiguous

faces of said disk and diaphragm being in contact, substantially as

described.

"2. As a means for effecting a varying surface contact in the circuit of

a speaking-telegraph transmitter, the combination of two electrodes,

one of plumbago or similar material, and both having broad surfaces in

vibratory contact with each other, substantially as described."

The advance that was brought about by Edison's carbon transmitter will

be more apparent if we glance first at the state of the art of telephony

prior to his invention.

Bell was undoubtedly the first inventor of the art of transmitting

speech over an electric circuit, but, with his particular form of

telephone, the field was circumscribed. Bell's telephone is shown in the

diagrammatic sectional sketch (Fig. 1).

In the drawing M is a bar magnet contained in the rubber case, L. A

bobbin, or coil of wire, B, surrounds one end of the magnet. A diaphragm

of soft iron is shown at D, and E is the mouthpiece. The wire terminals

of the coil, B, connect with the binding screws, C C.

The next illustration shows a pair of such telephones connected for use,

the working parts only being designated by the above reference letters.

It will be noted that the wire terminals are here put to their proper

uses, two being joined together to form a line of communication, and the

other two being respectively connected to "ground."

Now, if we imagine a person at each one of the instruments (Fig. 2) we

shall find that when one of them speaks the sound vibrations impinge

upon the diaphragm and cause it to act as a vibrating armature. By

reason of its vibrations, this diaphragm induces very weak electric

impulses in the magnetic coil. These impulses, according to Bell's

theory, correspond in form to the sound-waves, and, passing over the

line, energize the magnet coil at the receiving end, thus giving rise to

corresponding variations in magnetism by reason of which the receiving

diaphragm is similarly vibrated so as to reproduce the sounds. A single

apparatus at each end is therefore sufficient, performing the double

function of transmitter and receiver. It will be noticed that in this

arrangement no battery is used The strength of the impulses transmitted

is therefore limited to that of the necessarily weak induction currents

generated by the original sounds minus any loss arising by reason of

resistance in the line.

Edison's carbon transmitter overcame this vital or limiting weakness

by providing for independent power on the transmission circuit, and by

introducing the principle of varying the resistance of that circuit with

changes in the pressure. With Edison's telephone there is used a closed

circuit on which a battery current constantly flows, and in that

circuit is a pair of electrodes, one or both of which is carbon. These

electrodes are always in contact with a certain initial pressure,

so that current will be always flowing over the circuit. One of the

electrodes is connected with the diaphragm on which the sound-waves

impinge, and the vibrations of this diaphragm cause corresponding

variations in pressure between the electrodes, and thereby effect

similar variations in the current which is passing over the line to the

receiving end. This current, flowing around the receiving magnet, causes

corresponding impulses therein, which, acting upon its diaphragm, effect

a reproduction of the original vibrations and hence of the original

sounds.

In other words, the essential difference is that with Bell's telephone

the sound-waves themselves generate the electric impulses, which are

therefore extremely faint. With Edison's telephone the sound-waves

simply actuate an electric valve, so to speak, and permit variations in

a current of any desired strength.

A second distinction between the two telephones is this: With the Bell

apparatus the very weak electric impulses generated by the vibration of

the transmitting diaphragm pass over the entire line to the receiving

end, and, in consequence, the possible length of line is limited to

a few miles, even under ideal conditions. With Edison's telephone the

battery current does not flow on the main line, but passes through

the primary circuit of an induction-coil, from the secondary of which

corresponding impulses of enormously higher potential are sent out on

the main line to the receiving end. In consequence, the line may be

hundreds of miles in length. No modern telephone system is in use to-day

that does not use these characteristic features: the varying resistance

and the induction-coil. The system inaugurated by Edison is shown by the

diagram (Fig. 3), in which the carbon transmitter, the induction-coil,

the line, and the distant receiver are respectively indicated.

In Fig. 4 an early form of the Edison carbon transmitter is represented

in sectional view.

The carbon disk is represented by the black portion, E, near the

diaphragm, A, placed between two platinum plates D and G, which are

connected in the battery circuit, as shown by the lines. A small

piece of rubber tubing, B, is attached to the centre of the metallic

diaphragm, and presses lightly against an ivory piece, F, which is

placed directly over one of the platinum plates. Whenever, therefore,

any motion is given to the diaphragm, it is immediately followed by a

corresponding pressure upon the carbon, and by a change of resistance in

the latter, as described above.

It is interesting to note the position which Edison occupies in

the telephone art from a legal standpoint. To this end the reader's

attention is called to a few extracts from a decision of Judge Brown

in two suits brought in the United States Circuit Court, District

of Massachusetts, by the American Bell Telephone Company against the

National Telephone Manufacturing Company, et al., and Century Telephone

Company, et al., reported in Federal Reporter, 109, page 976, et seq.

These suits were brought on the Berliner patent, which, it was claimed,

covered broadly the electrical transmission of speech by variations of

pressure between opposing electrodes in constant contact. The Berliner

patent was declared invalid, and in the course of a long and exhaustive

opinion, in which the state of art and the work of Bell, Edison,

Berliner, and others was fully discussed, the learned Judge made the

following remarks: "The carbon electrode was the invention of Edison....

Edison preceded Berliner in the transmission of speech.... The carbon

transmitter was an experimental invention of a very high order of

merit.... Edison, by countless experiments, succeeded in advancing the

art. . . . That Edison did produce speech with solid electrodes before

Berliner is clearly proven.... The use of carbon in a transmitter is,

beyond controversy, the invention of Edison. Edison was the first to

make apparatus in which carbon was used as one of the electrodes....

The carbon transmitter displaced Bell's magnetic transmitter, and,

under several forms of construction, remains the only commercial

instrument.... The advance in the art was due to the carbon electrode of

Edison.... It is conceded that the Edison transmitter as apparatus is a

very important invention.... An immense amount of painstaking and highly

ingenious experiment preceded Edison's successful result. The discovery

of the availability of carbon was unquestionably invention, and it

resulted in the 'first practical success in the art.'"

VII. EDISON'S TASIMETER

THIS interesting and remarkable device is one of Edison's many

inventions not generally known to the public at large, chiefly because

the range of its application has been limited to the higher branches of

science. He never applied for a patent on the instrument, but dedicated

it to the public.

The device was primarily intended for use in detecting and measuring

infinitesimal degrees of temperature, however remote, and its conception

followed Edison's researches on the carbon telephone transmitter. Its

principle depends upon the variable resistance of carbon in accordance

with the degree of pressure to which it is subjected. By means of

this instrument, pressures that are otherwise inappreciable and

undiscoverable may be observed and indicated.

The detection of small variations of temperatures is brought about

through the changes which heat or cold will produce in a sensitive

material placed in contact with a carbon button, which is put in circuit

with a battery and delicate galvanometer. In the sketch (Fig. 1) there

is illustrated, partly in section, the form of tasimeter which Edison

took with him to Rawlins, Wyoming, in July, 1878, on the expedition to

observe the total eclipse of the sun.

The substance on whose expansion the working of the instrument depends

is a strip of some material extremely sensitive to heat, such as

vulcanite. shown at A, and firmly clamped at B. Its lower end fits into

a slot in a metal plate, C, which in turn rests upon a carbon button.

This latter and the metal plate are connected in an electric circuit

which includes a battery and a sensitive galvanometer. A vulcanite or

other strip is easily affected by differences of temperature,

expanding and contracting by reason of the minutest changes. Thus, an

infinitesimal variation in its length through expansion or contraction

changes the pressure on the carbon and affects the resistance of the

circuit to a corresponding degree, thereby causing a deflection of

the galvanometer; a movement of the needle in one direction denoting

expansion, and in the other contraction. The strip, A, is first put

under a slight pressure, deflecting the needle a few degrees from zero.

Any subsequent expansion or contraction of the strip may readily

be noted by further movements of the needle. In practice, and for

measurements of a very delicate nature, the tasimeter is inserted in one

arm of a Wheatstone bridge, as shown at A in the diagram (Fig. 2). The

galvanometer is shown at B in the bridge wire, and at C, D, and E there

are shown the resistances in the other arms of the bridge, which are

adjusted to equal the resistance of the tasimeter circuit. The battery

is shown at F. This arrangement tends to obviate any misleading

deflections that might arise through changes in the battery.

The dial on the front of the instrument is intended to indicate the

exact amount of physical expansion or contraction of the strip. This is

ascertained by means of a micrometer screw, S, which moves a needle, T,

in front of the dial. This screw engages with a second and similar screw

which is so arranged as to move the strip of vulcanite up or down. After

a galvanometer deflection has been obtained through the expansion or

contraction of the strip by reason of a change of temperature, a similar

deflection is obtained mechanically by turning the screw, S, one way or

the other. This causes the vulcanite strip to press more or less

upon the carbon button, and thus produces the desired change in the

resistance of the circuit. When the galvanometer shows the desired

deflection, the needle, T, will indicate upon the dial, in decimal

fractions of an inch, the exact distance through which the strip has

been moved.

With such an instrument as the above, Edison demonstrated the existence

of heat in the corona at the above-mentioned total eclipse of the sun,

but exact determinations could not be made at that time, because the

tasimeter adjustment was too delicate, and at the best the galvanometer

deflections were so marked that they could not be kept within the

limits of the scale. The sensitiveness of the instrument may be easily

comprehended when it is stated that the heat of the hand thirty feet

away from the cone-like funnel of the tasimeter will so affect the

galvanometer as to cause the spot of light to leave the scale.

This instrument can also be used to indicate minute changes of

moisture in the air by substituting a strip of gelatine in place of the

vulcanite. When so arranged a moistened piece of paper held several feet

away will cause a minute expansion of the gelatine strip, which

effects a pressure on the carbon, and causes a variation in the circuit

sufficient to throw the spot of light from the galvanometer mirror off

the scale.

The tasimeter has been used to demonstrate heat from remote stars

(suns), such as Arcturus.

VIII. THE EDISON PHONOGRAPH

THE first patent that was ever granted on a device for permanently

recording the human voice and other sounds, and for reproducing the same

audibly at any future time, was United States Patent No. 200,251, issued

to Thomas A. Edison on February 19, 1878, the application having

been filed December 24, 1877. It is worthy of note that no references

whatever were cited against the application while under examination in

the Patent Office. This invention therefore, marked the very beginning

of an entirely new art, which, with the new industries attendant upon

its development, has since grown to occupy a position of worldwide

reputation.

That the invention was of a truly fundamental character is also evident

from the fact that although all "talking-machines" of to-day differ very

widely in refinement from the first crude but successful phonograph of

Edison, their performance is absolutely dependent upon the employment of

the principles stated by him in his Patent No. 200,251. Quoting from the

specification attached to this patent, we find that Edison said:

"The invention consists in arranging a plate, diaphragm or other

flexible body capable of being vibrated by the human voice or other

sounds, in conjunction with a material capable of registering the

movements of such vibrating body by embossing or indenting or altering

such material, in such a manner that such register marks will be

sufficient to cause a second vibrating plate or body to be set in motion

by them, and thus reproduce the motions of the first vibrating body."

It will be at once obvious that these words describe perfectly the

basic principle of every modern phonograph or other talking-machine,

irrespective of its manufacture or trade name.

Edison's first model of the phonograph is shown in the following

illustration.

It consisted of a metallic cylinder having a helical indenting groove

cut upon it from end to end. This cylinder was mounted on a shaft

supported on two standards. This shaft at one end was fitted with a

handle, by means of which the cylinder was rotated. There were two

diaphragms, one on each side of the cylinder, one being for recording

and the other for reproducing speech or other sounds. Each diaphragm

had attached to it a needle. By means of the needle attached to the

recording diaphragm, indentations were made in a sheet of tin-foil

stretched over the peripheral surface of the cylinder when the diaphragm

was vibrated by reason of speech or other sounds. The needle on

the other diaphragm subsequently followed these indentations, thus

reproducing the original sounds.

Crude as this first model appears in comparison with machines of later

development and refinement, it embodied their fundamental essentials,

and was in fact a complete, practical phonograph from the first moment

of its operation.

The next step toward the evolution of the improved phonograph of to-day

was another form of tin-foil machine, as seen in the illustration.

It will be noted that this was merely an elaborated form of the first

model, and embodied several mechanical modifications, among which was

the employment of only one diaphragm for recording and reproducing.

Such was the general type of phonograph used for exhibition purposes

in America and other countries in the three or four years immediately

succeeding the date of this invention.

In operating the machine the recording diaphragm was advanced nearly

to the cylinder, so that as the diaphragm was vibrated by the voice the

needle would prick or indent a wave-like record in the tin-foil that

was on the cylinder. The cylinder was constantly turned during the

recording, and in turning, was simultaneously moved forward. Thus the

record would be formed on the tin-foil in a continuous spiral line.

To reproduce this record it was only necessary to again start at the

beginning and cause the needle to retrace its path in the spiral line.

The needle, in passing rapidly in contact with the recorded waves, was

vibrated up and down, causing corresponding vibrations of the diaphragm.

In this way sound-waves similar to those caused by the original sounds

would be set up in the air, thus reproducing the original speech.

The modern phonograph operates in a precisely similar way, the only

difference being in details of refinement. Instead of tin-foil, a wax

cylinder is employed, the record being cut thereon by a cutting-tool

attached to a diaphragm, while the reproduction is effected by means of

a blunt stylus similarly attached.

The cutting-tool and stylus are devices made of sapphire, a gem next in

hardness to a diamond, and they have to be cut and formed to an exact

nicety by means of diamond dust, most of the work being performed under

high-powered microscopes. The minute proportions of these devices will

be apparent by a glance at the accompanying illustrations, in which the

object on the left represents a common pin, and the objects on the right

the cutting-tool and reproducing stylus, all actual sizes.

In the next illustration (Fig. 4) there is shown in the upper sketch,

greatly magnified, the cutting or recording tool in the act of forming

the record, being vibrated rapidly by the diaphragm; and in the lower

sketch, similarly enlarged, a representation of the stylus travelling

over the record thus made, in the act of effecting a reproduction.

From the late summer of 1878 and to the fall of 1887 Edison was

intensely busy on the electric light, electric railway, and other

problems, and virtually gave no attention to the phonograph. Hence,

just prior to the latter-named period the instrument was still in its

tin-foil age; but he then began to devote serious attention to the

development of an improved type that should be of greater commercial

importance. The practical results are too well known to call for further

comment. That his efforts were not limited in extent may be inferred

from the fact that since the fall of 1887 to the present writing he has

been granted in the United States one hundred and four patents relating

to the phonograph and its accessories.

Interesting as the numerous inventions are, it would be a work of

supererogation to digest all these patents in the present pages, as they

represent not only the inception but also the gradual development and

growth of the wax-record type of phonograph from its infancy to the

present perfected machine and records now so widely known all over the

world. From among these many inventions, however, we will select two

or three as examples of ingenuity and importance in their bearing upon

present perfection of results.

One of the difficulties of reproduction for many years was the trouble

experienced in keeping the stylus in perfect engagement with the

wave-like record, so that every minute vibration would be reproduced. It

should be remembered that the deepest cut of the recording tool is only

about one-third the thickness of tissue-paper. Hence, it will be quite

apparent that the slightest inequality in the surface of the wax would

be sufficient to cause false vibration, and thus give rise to distorted

effects in such music or other sounds as were being reproduced. To

remedy this, Edison added an attachment which is called a "floating

weight," and is shown at A in the illustration above.

The function of the floating weight is to automatically keep the

stylus in close engagement with the record, thus insuring accuracy of

reproduction. The weight presses the stylus to its work, but because

of its mass it cannot respond to the extremely rapid vibrations of the

stylus. They are therefore communicated to the diaphragm.

Some of Edison's most remarkable inventions are revealed in a number of

interesting patents relating to the duplication of phonograph records.

It would be obviously impossible, from a commercial standpoint, to

obtain a musical record from a high-class artist and sell such an

original to the public, as its cost might be from one hundred to several

thousand dollars. Consequently, it is necessary to provide some way by

which duplicates may be made cheaply enough to permit their purchase by

the public at a reasonable price.

The making of a perfect original musical or other record is a matter

of no small difficulty, as it requires special technical knowledge and

skill gathered from many years of actual experience; but in the exact

copying, or duplication, of such a record, with its many millions

of microscopic waves and sub-waves, the difficulties are enormously

increased. The duplicates must be microscopically identical with the

original, they must be free from false vibrations or other defects,

although both original and duplicates are of such easily defacable

material as wax; and the process must be cheap and commercial not a

scientific laboratory possibility.

For making duplicates it was obviously necessary to first secure a mold

carrying the record in negative or reversed form. From this could be

molded, or cast, positive copies which would be identical with the

original. While the art of electroplating would naturally suggest

itself as the means of making such a mold, an apparently insurmountable

obstacle appeared on the very threshold. Wax, being a non-conductor,

cannot be electroplated unless a conducting surface be first applied.

The coatings ordinarily used in electro-deposition were entirely out of

the question on account of coarseness, the deepest waves of the record

being less than one-thousandth of an inch in depth, and many of them

probably ten to one hundred times as shallow. Edison finally decided

to apply a preliminary metallic coating of infinitesimal thinness, and

accomplished this object by a remarkable process known as the vacuous

deposit. With this he applied to the original record a film of gold

probably no thicker than one three-hundred-thousandth of an inch, or

several hundred times less than the depth of an average wave. Three

hundred such layers placed one on top of the other would make a sheet no

thicker than tissue-paper.

The process consists in placing in a vacuum two leaves, or electrodes,

of gold, and between them the original record. A constant discharge of

electricity of high tension between the electrodes is effected by means

of an induction-coil. The metal is vaporized by this discharge, and is

carried by it directly toward and deposited upon the original record,

thus forming the minute film of gold above mentioned. The record is

constantly rotated until its entire surface is coated. A sectional

diagram of the apparatus (Fig. 6.) will aid to a clearer understanding

of this ingenious process.

After the gold film is formed in the manner described above, a heavy

backing of baser metal is electroplated upon it, thus forming a

substantial mold, from which the original record is extracted by

breakage or shrinkage.

Duplicate records in any quantity may now be made from this mold by

surrounding it with a cold-water jacket and dipping it in a molten

wax-like material. This congeals on the record surface just as melted

butter would collect on a cold knife, and when the mold is removed the

surplus wax falls out, leaving a heavy deposit of the material which

forms the duplicate record. Numerous ingenious inventions have been made

by Edison providing for a variety of rapid and economical methods

of duplication, including methods of shrinking a newly made copy to

facilitate its quick removal from the mold; methods of reaming, of

forming ribs on the interior, and for many other important and essential

details, which limits of space will not permit of elaboration. Those

mentioned above are but fair examples of the persistent and effective

work he has done to bring the phonograph to its present state of

perfection.

In perusing Chapter X of the foregoing narrative, the reader undoubtedly

noted Edison's clear apprehension of the practical uses of the

phonograph, as evidenced by his prophetic utterances in the article

written by him for the North American Review in June, 1878. In view of

the crudity of the instrument at that time, it must be acknowledged that

Edison's foresight, as vindicated by later events was most remarkable.

No less remarkable was his intensely practical grasp of mechanical

possibilities of future types of the machine, for we find in one of his

early English patents (No. 1644 of 1878) the disk form of phonograph

which, some ten to fifteen years later, was supposed to be a new

development in the art. This disk form was also covered by Edison's

application for a United States patent, filed in 1879. This application

met with some merely minor technical objections in the Patent Office,

and seems to have passed into the "abandoned" class for want of

prosecution, probably because of being overlooked in the tremendous

pressure arising from his development of his electric-lighting system.

IX. THE INCANDESCENT LAMP

ALTHOUGH Edison's contributions to human comfort and progress are

extensive in number and extraordinarily vast and comprehensive in

scope and variety, the universal verdict of the world points to his

incandescent lamp and system of distribution of electrical current as

the central and crowning achievements of his life up to this time. This

view would seem entirely justifiable when we consider the wonderful

changes in the conditions of modern life that have been brought about

by the wide-spread employment of these inventions, and the gigantic

industries that have grown up and been nourished by their world-wide

application. That he was in this instance a true pioneer and creator

is evident as we consider the subject, for the United States Patent No.

223,898, issued to Edison on January 27, 1880, for an incandescent lamp,

was of such fundamental character that it opened up an entirely new and

tremendously important art--the art of incandescent electric lighting.

This statement cannot be successfully controverted, for it has been

abundantly verified after many years of costly litigation. If further

proof were desired, it is only necessary to point to the fact that,

after thirty years of most strenuous and practical application in the

art by the keenest intellects of the world, every incandescent lamp

that has ever since been made, including those of modern days, is

still dependent upon the employment of the essentials disclosed in the

above-named patent--namely, a filament of high resistance enclosed in

a sealed glass globe exhausted of air, with conducting wires passing

through the glass.

An incandescent lamp is such a simple-appearing article--merely a

filament sealed into a glass globe--that its intrinsic relation to the

art of electric lighting is far from being apparent at sight. To the lay

mind it would seem that this must have been THE obvious device to make

in order to obtain electric light by incandescence of carbon or

other material. But the reader has already learned from the preceding

narrative that prior to its invention by Edison such a device was NOT

obvious, even to the most highly trained experts of the world at that

period; indeed, it was so far from being obvious that, for some time

after he had completed practical lamps and was actually lighting them up

twenty-four hours a day, such a device and such a result were declared

by these same experts to be an utter impossibility. For a short while

the world outside of Menlo Park held Edison's claims in derision.

His lamp was pronounced a fake, a myth, possibly a momentary success

magnified to the dignity of a permanent device by an overenthusiastic

inventor.

Such criticism, however, did not disturb Edison. He KNEW that he had

reached the goal. Long ago, by a close process of reasoning, he had

clearly seen that the only road to it was through the path he had

travelled, and which was now embodied in the philosophy of his

incandescent lamp--namely, a filament, or carbon, of high resistance and

small radiating surface, sealed into a glass globe exhausted of air to a

high degree of vacuum. In originally committing himself to this line

of investigation he was well aware that he was going in a direction

diametrically opposite to that followed by previous investigators. Their

efforts had been confined to low-resistance burners of large radiating

surface for their lamps, but he realized the utter futility of such

devices. The tremendous problems of heat and the prohibitive quantities

of copper that would be required for conductors for such lamps would be

absolutely out of the question in commercial practice.

He was convinced from the first that the true solution of the

problem lay in a lamp which should have as its illuminating body

a strip of material which would offer such a resistance to

the flow of electric current that it could be raised to a high

temperature--incandescence--and be of such small cross-section that it

would radiate but little heat. At the same time such a lamp must require

a relatively small amount of current, in order that comparatively small

conductors could be used, and its burner must be capable of withstanding

the necessarily high temperatures without disintegration.

It is interesting to note that these conceptions were in Edison's mind

at an early period of his investigations, when the best expert opinion

was that the subdivision of the electric current was an ignis fatuus.

Hence we quote the following notes he made, November 15, 1878, in one of

the laboratory note-books:

"A given straight wire having 1 ohm resistance and certain length is

brought to a given degree of temperature by given battery. If the same

wire be coiled in such a manner that but one-quarter of its surface

radiates, its temperature will be increased four times with the

same battery, or, one-quarter of this battery will bring it to the

temperature of straight wire. Or the same given battery will bring

a wire whose total resistance is 4 ohms to the same temperature as

straight wire.

"This was actually determined by trial.

"The amount of heat lost by a body is in proportion to the radiating

surface of that body. If one square inch of platina be heated to 100

degrees it will fall to, say, zero in one second, whereas, if it was at

200 degrees it would require two seconds.

"Hence, in the case of incandescent conductors, if the radiating surface

be twelve inches and the temperature on each inch be 100, or 1200 for

all, if it is so coiled or arranged that there is but one-quarter, or

three inches, of radiating surface, then the temperature on each inch

will be 400. If reduced to three-quarters of an inch it will have on

that three-quarters of an inch 1600 degrees Fahr., notwithstanding

the original total amount was but 1200, because the radiation has

been reduced to three-quarters, or 75 units; hence, the effect of the

lessening of the radiation is to raise the temperature of each remaining

inch not radiating to 125 degrees. If the radiating surface should be

reduced to three-thirty-seconds of an inch, the temperature would reach

6400 degrees Fahr. To carry out this law to the best advantage in regard

to platina, etc., then with a given length of wire to quadruple the heat

we must lessen the radiating surface to one-quarter, and to do this in a

spiral, three-quarters must be within the spiral and one-quarter outside

for radiating; hence, a square wire or other means, such as a spiral

within a spiral, must be used. These results account for the enormous

temperature of the Electric Arc with one horse-power; as, for instance,

if one horse-power will heat twelve inches of wire to 1000 degrees

Fahr., and this is concentrated to have one-quarter of the radiating

surface, it would reach a temperature of 4000 degrees or sufficient

to melt it; but, supposing it infusible, the further concentration to

one-eighth its surface, it would reach a temperature of 16,000 degrees,

and to one-thirty-second its surface, which would be about the radiating

surface of the Electric Arc, it would reach 64,000 degrees Fahr. Of

course, when Light is radiated in great quantities not quite these

temperatures would be reached.

"Another curious law is this: It will require a greater initial battery

to bring an iron wire of the same size and resistance to a given

temperature than it will a platina wire in proportion to their specific

heats, and in the case of Carbon, a piece of Carbon three inches long

and one-eighth diameter, with a resistance of 1 ohm, will require a

greater battery power to bring it to a given temperature than a cylinder

of thin platina foil of the same length, diameter, and resistance,

because the specific heat of Carbon is many times greater; besides, if

I am not mistaken, the radiation of a roughened body for heat is greater

than a polished one like platina."

Proceeding logically upon these lines of thought and following them

out through many ramifications, we have seen how he at length made a

filament of carbon of high resistance and small radiating surface, and

through a concurrent investigation of the phenomena of high vacua and

occluded gases was able to produce a true incandescent lamp. Not only

was it a lamp as a mere article--a device to give light--but it was also

an integral part of his great and complete system of lighting, to every

part of which it bore a fixed and definite ratio, and in relation to

which it was the keystone that held the structure firmly in place.

The work of Edison on incandescent lamps did not stop at this

fundamental invention, but extended through more than eighteen years

of a most intense portion of his busy life. During that period he was

granted one hundred and forty-nine other patents on the lamp and its

manufacture. Although very many of these inventions were of the utmost

importance and value, we cannot attempt to offer a detailed exposition

of them in this necessarily brief article, but must refer the reader,

if interested, to the patents themselves, a full list being given at

the end of this Appendix. The outline sketch will indicate the principal

patents covering the basic features of the lamp.

The litigation on the Edison lamp patents was one of the most determined

and stubbornly fought contests in the history of modern jurisprudence.

Vast interests were at stake. All of the technical, expert, and

professional skill and knowledge that money could procure or experience

devise were availed of in the bitter fights that raged in the courts for

many years. And although the Edison interests had spent from first to

last nearly $2,000,000, and had only about three years left in the

life of the fundamental patent, Edison was thoroughly sustained as to

priority by the decisions in the various suits. We shall offer a few

brief extracts from some of these decisions.

In a suit against the United States Electric Lighting Company, United

States Circuit Court for the Southern District of New York, July 14,

1891, Judge Wallace said, in his opinion: "The futility of hoping to

maintain a burner in vacuo with any permanency had discouraged prior

inventors, and Mr. Edison is entitled to the credit of obviating the

mechanical difficulties which disheartened them.... He was the first

to make a carbon of materials, and by a process which was especially

designed to impart high specific resistance to it; the first to make a

carbon in the special form for the special purpose of imparting to it

high total resistance; and the first to combine such a burner with the

necessary adjuncts of lamp construction to prevent its disintegration

and give it sufficiently long life. By doing these things he made a lamp

which was practically operative and successful, the embryo of the best

lamps now in commercial use, and but for which the subdivision of the

electric light by incandescence would still be nothing but the ignis

fatuus which it was proclaimed to be in 1879 by some of the reamed

experts who are now witnesses to belittle his achievement and show that

it did not rise to the dignity of an invention.... It is impossible to

resist the conclusion that the invention of the slender thread of carbon

as a substitute for the burners previously employed opened the path to

the practical subdivision of the electric light."

An appeal was taken in the above suit to the United States Circuit Court

of Appeals, and on October 4, 1892, the decree of the lower court was

affirmed. The judges (Lacombe and Shipman), in a long opinion reviewed

the facts and the art, and said, inter alia: "Edison's invention was

practically made when he ascertained the theretofore unknown fact that

carbon would stand high temperature, even when very attenuated, if

operated in a high vacuum, without the phenomenon of disintegration.

This fact he utilized by the means which he has described, a lamp having

a filamentary carbon burner in a nearly perfect vacuum."

In a suit against the Boston Incandescent Lamp Company et al., in the

United States Circuit Court for the District of Massachusetts, decided

in favor of Edison on June 11, 1894, Judge Colt, in his opinion, said,

among other things: "Edison made an important invention; he produced the

first practical incandescent electric lamp; the patent is a pioneer in

the sense of the patent law; it may be said that his invention created

the art of incandescent electric lighting."

Opinions of other courts, similar in tenor to the foregoing, might be

cited, but it would be merely in the nature of reiteration. The above

are sufficient to illustrate the direct clearness of judicial decision

on Edison's position as the founder of the art of electric lighting by

incandescence.

X. EDISON'S DYNAMO WORK

AT the present writing, when, after the phenomenally rapid electrical

development of thirty years, we find on the market a great variety of

modern forms of efficient current generators advertised under the names

of different inventors (none, however, bearing the name of Edison), a

young electrical engineer of the present generation might well inquire

whether the great inventor had ever contributed anything to the art

beyond a mere TYPE of machine formerly made and bearing his name, but

not now marketed except second hand.

For adequate information he might search in vain the books usually

regarded as authorities on the subject of dynamo-electric machinery,

for with slight exceptions there has been a singular unanimity in

the omission of writers to give Edison credit for his great and basic

contributions to heavy-current technics, although they have been

universally acknowledged by scientific and practical men to have laid

the foundation for the efficiency of, and to be embodied in all modern

generators of current.

It might naturally be expected that the essential facts of Edison's

work would appear on the face of his numerous patents on dynamo-electric

machinery, but such is not necessarily the case, unless they are

carefully studied in the light of the state of the art as it existed

at the time. While some of these patents (especially the earlier ones)

cover specific devices embodying fundamental principles that not only

survive to the present day, but actually lie at the foundation of

the art as it now exists, there is no revelation therein of Edison's

preceding studies of magnets, which extended over many years, nor of his

later systematic investigations and deductions.

Dynamo-electric machines of a primitive kind had been invented and were

in use to a very limited extent for arc lighting and electroplating for

some years prior to the summer of 1819, when Edison, with an embryonic

lighting SYSTEM in mind, cast about for a type of machine technically

and commercially suitable for the successful carrying out of his plans.

He found absolutely none. On the contrary, all of the few types then

obtainable were uneconomical, indeed wasteful, in regard to efficiency.

The art, if indeed there can be said to have been an art at that time,

was in chaotic confusion, and only because of Edison's many years' study

of the magnet was he enabled to conclude that insufficiency in quantity

of iron in the magnets of such machines, together with poor surface

contacts, rendered the cost of magnetization abnormally high. The

heating of solid armatures, the only kind then known, and poor

insulation in the commutators, also gave rise to serious losses. But

perhaps the most serious drawback lay in the high-resistance armature,

based upon the highest scientific dictum of the time that in order

to obtain the maximum amount of work from a machine, the internal

resistance of the armature must equal the resistance of the exterior

circuit, although the application of this principle entailed the useless

expenditure of at least 50 per cent. of the applied energy.