Full Text Archive logoFull Text Archive — Free Classic E-books

Faraday As A Discoverer by John Tyndall

Part 1 out of 3

Adobe PDF icon
Download this document as a .pdf
File size: 0.3 MB
What's this? light bulb idea Many people prefer to read off-line or to print out text and read from the real printed page. Others want to carry documents around with them on their mobile phones and read while they are on the move. We have created .pdf files of all out documents to accommodate all these groups of people. We recommend that you download .pdfs onto your mobile phone when it is connected to a WiFi connection for reading off-line.

Faraday As A Discoverer, by John Tyndall



Chapter 1.
Parentage: introduction to the royal institution:
earliest experiments: first royal society paper: marriage.

Chapter 2.
Early researches: magnetic rotations: liquefaction of gases:
heavy glass: Charles Anderson: contributions to physics.

Chapter 3.
Discovery of Magneto-electricity: Explanation of Argo's magnetism
of rotation: Terrestrial magneto-electric induction:
The extra current.

Chapter 4.
Points of Character.

Chapter 5.
Identity of electricities; first researches on electro-chemistry.

Chapter 6.
Laws of electro-chemical decomposition.

Chapter 7.
Origin of power in the voltaic pile.

Chapter 8.
Researches on frictional electricity: induction: conduction:
specific inductive capacity: theory of contiguous particles.

Chapter 9.
Rest needed--visit to Switzerland.

Chapter 10.
Magnetization of light.

Chapter 11.
Discovery of diamagnetism--researches on magne-crystallic action.

Chapter 12.
Magnetism of flame and gases--atmospheric magnetism.

Chapter 13.
Speculations: nature of matter: lines of force.

Chapter 14.
Unity and convertibility of natural forces: theory of the
electric current.

Chapter 15.

Chapter 16.
Illustrations of Character.

Preface to the fifth edition.

Daily and weekly, from all parts of the world, I receive publications
bearing upon the practical applications of electricity. This great
movement, the ultimate outcome of which is not to be foreseen, had
its origin in the discoveries made by Michael Faraday, sixty-two
years ago. From these discoveries have sprung applications of the
telephone order, together with various forms of the electric
telegraph. From them have sprung the extraordinary advances made in
electrical illumination. Faraday could have had but an imperfect
notion of the expansions of which his discoveries were capable.
Still he had a vivid and strong imagination, and I do not doubt that
he saw possibilities which did not disclose themselves to the
general scientific mind. He knew that his discoveries had their
practical side, but he steadfastly resisted the seductions of this
side, applying himself to the development of principles; being well
aware that the practical question would receive due development

During my sojourn in Switzerland this year, I read through the
proofs of this new edition, and by my reading was confirmed in the
conviction that the book ought not to be suffered to go out of
print. The memoir was written under great pressure, but I am not
ashamed of it as it stands. Glimpses of Faraday's character and
gleams of his discoveries are there to be found which will be of
interest to humanity to the end of time.

John Tyndall.
Hind Head,
December, 1893.

[Note.--It was, I believe, my husband's intention to substitute
this Preface, written a few days before his death, for all former
Prefaces. As, however, he had not the opportunity of revising the
old prefatory pages himself, they have been allowed to remain just
as they stood in the last edition.

Louisa C. Tyndall.]

Preface to the fourth edition.

When consulted a short time ago as to the republication of 'Faraday
as a Discoverer,' it seemed to me that the labours, and points of
character, of so great a worker and so good a man should not be
allowed to vanish from the public eye. I therefore willingly fell
in with the proposal of my Publishers to issue a new edition of the
little book.

Royal Institution,
February, 1884.

Preface to the second edition.

The experimental researches of Faraday are so voluminous,
their descriptions are so detailed, and their wealth of illustration
is so great, as to render it a heavy labour to master them.
The multiplication of proofs, necessary and interesting when the new
truths had to be established, are however less needful now when
these truths have become household words in science. I have
therefore tried in the following pages to compress the body, without
injury to the spirit, of these imperishable investigations, and to
present them in a form which should be convenient and useful to the
student of the present day.

While I write, the volumes of the Life of Faraday by Dr. Bence
Jones have reached my hands. To them the reader must refer for an
account of Faraday's private relations. A hasty glance at the work
shows me that the reverent devotion of the biographer has turned to
admirable account the materials at his command.

The work of Dr. Bence Jones enables me to correct a statement
regarding Wollaston's and Faraday's respective relations to the
discovery of Magnetic Rotation. Wollaston's idea was to make the
wire carrying a current rotate round its own axis: an idea
afterwards realised by the celebrated Ampere. Faraday's discovery
was to make the wire carrying the current revolve round the pole of
a magnet and the reverse.

John Tyndall.
Royal Institution:
December, 1869.


Chapter 1.

Parentage: introduction to the royal institution:
earliest experiments: first royal society paper: marriage.

It has been thought desirable to give you and the world some image
of MICHAEL FARADAY, as a scientific investigator and discoverer.
The attempt to respond to this desire has been to me a labour of
difficulty, if also a labour of love. For however well acquainted
I may be with the researches and discoveries of that great
master--however numerous the illustrations which occur to me of the
loftiness of Faraday's character and the beauty of his life--still
to grasp him and his researches as a whole; to seize upon the ideas
which guided him, and connected them; to gain entrance into that
strong and active brain, and read from it the riddle of the world--
this is a work not easy of performance, and all but impossible amid
the distraction of duties of another kind. That I should at one
period or another speak to you regarding Faraday and his work is
natural, if not inevitable; but I did not expect to be called upon
to speak so soon. Still the bare suggestion that this is the fit
and proper time for speech sent me immediately to my task: from it
I have returned with such results as I could gather, and also with
the wish that those results were more worthy than they are of the
greatness of my theme.

It is not my intention to lay before you a life of Faraday in the
ordinary acceptation of the term. The duty I have to perform is
to give you some notion of what he has done in the world; dwelling
incidentally on the spirit in which his work was executed,
and introducing such personal traits as may be necessary to the
completion of your picture of the philosopher, though by no means
adequate to give you a complete idea of the man.

The newspapers have already informed you that Michael Faraday was
born at Newington Butts, on September 22, 1791, and that he died at
Hampton Court, on August 25, 1867. Believing, as I do, in the
general truth of the doctrine of hereditary transmission--sharing
the opinion of Mr. Carlyle, that 'a really able man never proceeded
from entirely stupid parents'--I once used the privilege of my
intimacy with Mr. Faraday to ask him whether his parents showed any
signs of unusual ability. He could remember none. His father,
I believe, was a great sufferer during the latter years of his life,
and this might have masked whatever intellectual power he possessed.
When thirteen years old, that is to say in 1804, Faraday was
apprenticed to a bookseller and bookbinder in Blandford Street,
Manchester Square: here he spent eight years of his life, after
which he worked as a journeyman elsewhere.

You have also heard the account of Faraday's first contact with the
Royal Institution; that he was introduced by one of the members to
Sir Humphry Davy's last lectures, that he took notes of those
lectures; wrote them fairly out, and sent them to Davy, entreating
him at the same time to enable him to quit trade, which he detested,
and to pursue science, which he loved. Davy was helpful to the young
man, and this should never be forgotten: he at once wrote to
Faraday, and afterwards, when an opportunity occurred, made him his
assistant.[1] Mr. Gassiot has lately favoured me with the following
reminiscence of this time:--

'Clapham Common, Surrey,
'November 28, 1867.

'My Dear Tyndall,--Sir H. Davy was accustomed to call on the late
Mr. Pepys, in the Poultry, on his way to the London Institution, of
which Pepys was one of the original managers; the latter told me
that on one occasion Sir H. Davy, showing him a letter, said:
"Pepys, what am I to do, here is a letter from a young man named
Faraday; he has been attending my lectures, and wants me to give him
employment at the Royal Institution--what can I do?" "Do?" replied
Pepys, "put him to wash bottles; if he is good for anything he will
do it directly, if he refuses he is good for nothing." "No, no,"
replied Davy; "we must try him with something better than that."
The result was, that Davy engaged him to assist in the Laboratory
at weekly wages.

'Davy held the joint office of Professor of Chemistry and Director
of the Laboratory; he ultimately gave up the former to the late
Professor Brande, but he insisted that Faraday should be appointed
Director of the Laboratory, and, as Faraday told me, this enabled
him on subsequent occasions to hold a definite position in the
Institution, in which he was always supported by Davy.
I believe he held that office to the last.

'Believe me, my dear Tyndall, yours truly,

'J. P. Gassiot.

'Dr. Tyndall.'

From a letter written by Faraday himself soon after his appointment
as Davy's assistant, I extract the following account of his
introduction to the Royal Institution:--
'London, Sept. 13, 1813.

'As for myself, I am absent (from home) nearly day and night, except
occasional calls, and it is likely shall shortly be absent entirely,
but this (having nothing more to say, and at the request of my
mother) I will explain to you. I was formerly a bookseller and
binder, but am now turned philosopher,[2] which happened thus:--
Whilst an apprentice, I, for amusement, learnt a little chemistry
and other parts of philosophy, and felt an eager desire to proceed
in that way further. After being a journeyman for six months,
under a disagreeable master, I gave up my business, and through
the interest of a Sir H. Davy, filled the situation of chemical
assistant to the Royal Institution of Great Britain, in which office
I now remain; and where I am constantly employed in observing the
works of nature, and tracing the manner in which she directs the
order and arrangement of the world. I have lately had proposals
made to me by Sir Humphry Davy to accompany him in his travels
through Europe and Asia, as philosophical assistant. If I go at all
I expect it will be in October next--about the end; and my absence
from home will perhaps be as long as three years. But as yet all is

This account is supplemented by the following letter, written by
Faraday to his friend De la Rive,[3] on the occasion of the death
of Mrs. Marcet. The letter is dated September 2, 1858:--

'My Dear Friend,--Your subject interested me deeply every way;
for Mrs. Marcet was a good friend to me, as she must have been to
many of the human race. I entered the shop of a bookseller and
bookbinder at the age of thirteen, in the year 1804, remained there
eight years, and during the chief part of my time bound books.
Now it was in those books, in the hours after work, that I found
the beginning of my philosophy.

There were two that especially helped me, the "Encyclopaedia
Britannica," from which I gained my first notions of electricity,
and Mrs. Marcet's "Conversation on Chemistry," which gave me my
foundation in that science.

'Do not suppose that I was a very deep thinker, or was marked as a
precocious person. I was a very lively imaginative person, and
could believe in the "Arabian Nights" as easily as in the
"Encyclopaedia." But facts were important to me, and saved me.
I could trust a fact, and always cross-examined an assertion.
So when I questioned Mrs. Marcet's book by such little experiments
as I could find means to perform, and found it true to the facts as
I could understand them, I felt that I had got hold of an anchor in
chemical knowledge, and clung fast to it. Thence my deep veneration
for Mrs. Marcet--first as one who had conferred great personal good
and pleasure on me; and then as one able to convey the truth and
principle of those boundless fields of knowledge which concern
natural things to the young, untaught, and inquiring mind.

'You may imagine my delight when I came to know Mrs. Marcet
personally; how often I cast my thoughts backward, delighting to
connect the past and the present; how often, when sending a paper
to her as a thank-offering, I thought of my first instructress,
and such like thoughts will remain with me.

'I have some such thoughts even as regards your own father; who was,
I may say, the first who personally at Geneva, and afterwards by
correspondence, encouraged, and by that sustained me.'

Twelve or thirteen years ago Mr. Faraday and myself quitted the
Institution one evening together, to pay a visit to our friend Grove
in Baker Street. He took my arm at the door, and, pressing it to
his side in his warm genial way, said, 'Come, Tyndall, I will now
show you something that will interest you.' We walked northwards,
passed the house of Mr. Babbage, which drew forth a reference to the
famous evening parties once assembled there. We reached Blandford
Street, and after a little looking about he paused before a
stationer's shop, and then went in. On entering the shop, his usual
animation seemed doubled; he looked rapidly at everything it
contained. To the left on entering was a door, through which he
looked down into a little room, with a window in front facing
Blandford Street. Drawing me towards him, he said eagerly,
'Look there, Tyndall, that was my working-place. I bound books in
that little nook.' A respectable-looking woman stood behind the
counter: his conversation with me was too low to be heard by her,
and he now turned to the counter to buy some cards as an excuse for
our being there. He asked the woman her name--her predecessor's
name-- his predecessor's name. 'That won't do,' he said, with
good-humoured impatience; 'who was his predecessor?' 'Mr. Riebau,'
she replied, and immediately added, as if suddenly recollecting
herself, 'He, sir, was the master of Sir Charles Faraday.'
'Nonsense!' he responded, 'there is no such person.' Great was her
delight when I told her the name of her visitor; but she assured me
that as soon as she saw him running about the shop, she felt-though
she did not know why--that it must be 'Sir Charles Faraday.'

Faraday did, as you know, accompany Davy to Rome: he was re-engaged
by the managers of the Royal Institution on May 15, 1815. Here he
made rapid progress in chemistry, and after a time was entrusted
with easy analyses by Davy. In those days the Royal Institution
published 'The Quarterly Journal of Science,' the precursor of our
own 'Proceedings.' Faraday's first contribution to science appeared
in that journal in 1816. It was an analysis of some caustic lime
from Tuscany, which had been sent to Davy by the Duchess of Montrose.
Between this period and 1818 various notes and short papers
were published by Faraday. In 1818 he experimented upon
'Sounding Flames.' Professor Auguste De la Rive had investigated
those sounding flames, and had applied to them an explanation which
completely accounted for a class of sounds discovered by himself,
but did not account for those known to his predecessors. By a few
simple and conclusive experiments, Faraday proved the explanation
insufficient. It is an epoch in the life of a young man when he
finds himself correcting a person of eminence, and in Faraday's
case, where its effect was to develop a modest self-trust, such an
event could not fail to act profitably.

From time to time between 1818 and 1820 Faraday published scientific
notes and notices of minor weight. At this time he was acquiring,
not producing; working hard for his master and storing and
strengthening his own mind. He assisted Mr. Brande in his lectures,
and so quietly, skilfully, and modestly was his work done, that
Mr. Brande's vocation at the time was pronounced 'lecturing on velvet.'
In 1820 Faraday published a chemical paper 'on two new compounds of
chlorine and carbon, and on a new compound of iodine, carbon,
and hydrogen.' This paper was read before the Royal Society on
December 21, 1820, and it was the first of his that was honoured
with a place in the 'Philosophical Transactions.'

On June 12, 1821, he married, and obtained leave to bring his young
wife into his rooms at the Royal Institution. There for forty-six
years they lived together, occupying the suite of apartments which
had been previously in the successive occupancy of Young, Davy, and
Brande. At the time of her marriage Mrs. Faraday was twenty-one
years of age, he being nearly thirty. Regarding this marriage I will
at present limit myself to quoting an entry written in Faraday's own
hand in his book of diplomas, which caught my eye while in his
company some years ago. It ran thus:--

'25th January, 1847.
'Amongst these records and events, I here insert the date of one
which, as a source of honour and happiness, far exceeds all the
rest. We were married on June 12, 1821.

'M. Faraday.'

Then follows the copy of the minutes, dated May 21, 1821, which gave
him additional rooms, and thus enabled him to bring his wife to the
Royal Institution. A feature of Faraday's character which I have
often noticed makes itself apparent in this entry. In his relations
to his wife he added chivalry to affection.

Footnotes to Chapter 1

[1] Here is Davy's recommendation of Faraday, presented to the
managers of the Royal Institution, at a meeting on the 18th of
March, 1813, Charles Hatchett, Esq., in the chair:--

'Sir Humphry Davy has the honour to inform the managers that he has
found a person who is desirous to occupy the situation in the
Institution lately filled by William Payne. His name is Michael
Faraday. He is a youth of twenty-two years of age. As far as Sir H.
Davy has been able to observe or ascertain, he appears well fitted
for the situation. His habits seem good; his disposition active and
cheerful, and his manner intelligent. He is willing to engage
himself on the same terms as given to Mr. Payne at the time of
quitting the Institution.

'Resolved,--That Michael Faraday be engaged to fill the situation
lately occupied by Mr. Payne, on the same terms.'

[2] Faraday loved this word and employed it to the last; he had an
intense dislike to the modern term physicist.

[3] To whom I am indebted for a copy of the original letter.

Chapter 2.

Early researches: magnetic rotations: liquefaction of gases:
heavy glass: Charles Anderson: contributions to physics.

Oersted, in 1820, discovered the action of a voltaic current on a
magnetic needle; and immediately afterwards the splendid intellect
of Ampere succeeded in showing that every magnetic phenomenon then
known might be reduced to the mutual action of electric currents.
The subject occupied all men's thoughts: and in this country
Dr. Wollaston sought to convert the deflection of the needle by the
current into a permanent rotation of the needle round the current.
He also hoped to produce the reciprocal effect of causing a current
to rotate round a magnet. In the early part of 1821, Wollaston
attempted to realise this idea in the presence of Sir Humphry Davy
in the laboratory of the Royal Institution.[1] This was well
calculated to attract Faraday's attention to the subject. He read
much about it; and in the months of July, August, and September he
wrote a 'history of the progress of electro-magnetism,' which he
published in Thomson's 'Annals of Philosophy.' Soon afterwards he
took up the subject of 'Magnetic Rotations,' and on the morning of
Christmas-day, 1821, he called his wife to witness, for the first
time, the revolution of a magnetic needle round an electric current.
Incidental to the 'historic sketch,' he repeated almost all the
experiments there referred to; and these, added to his own
subsequent work, made him practical master of all that was then
known regarding the voltaic current. In 1821, he also touched upon
a subject which subsequently received his closer attention--the
vaporization of mercury at common temperatures; and immediately
afterwards conducted, in company with Mr. Stodart, experiments on
the alloys of steel. He was accustomed in after years to present to
his friends razors formed from one of the alloys then discovered.

During Faraday's hours of liberty from other duties, he took up
subjects of inquiry for himself; and in the spring of 1823, thus
self-prompted, he began the examination of a substance which had
long been regarded as the chemical element chlorine, in a solid
form, but which Sir Humphry Davy, in 1810, had proved to be a
hydrate of chlorine, that is, a compound of chlorine and water.
Faraday first analysed this hydrate, and wrote out an account of its
composition. This account was looked over by Davy, who suggested
the heating of the hydrate under pressure in a sealed glass tube.
This was done. The hydrate fused at a blood-heat, the tube became
filled with a yellow atmosphere, and was afterwards found to contain
two liquid substances. Dr. Paris happened to enter the laboratory
while Faraday was at work. Seeing the oily liquid in his tube, he
rallied the young chemist for his carelessness in employing soiled
vessels. On filing off the end of the tube, its contents exploded
and the oily matter vanished. Early next morning, Dr. Paris
received the following note:--

'Dear Sir,--The oil you noticed yesterday turns out to be
liquid chlorine.

'Yours faithfully,
'M. Faraday.'[2]

The gas had been liquefied by its own pressure. Faraday then tried
compression with a syringe, and succeeded thus in liquefying the gas.

To the published account of this experiment Davy added the following
note:--'In desiring Mr. Faraday to expose the hydrate of chlorine in
a closed glass tube, it occurred to me that one of three things
would happen: that decomposition of water would occur;... or that
the chlorine would separate in a fluid state.' Davy, moreover,
immediately applied the method of self-compressing atmosphere to the
liquefaction of muriatic gas. Faraday continued the experiments,
and succeeded in reducing a number of gases till then deemed permanent
to the liquid condition. In 1844 he returned to the subject, and
considerably expanded its limits. These important investigations
established the fact that gases are but the vapours of liquids
possessing a very low boiling-point, and gave a sure basis to our
views of molecular aggregation. The account of the first investigation
was read before the Royal Society on April 10, 1823, and was
published, in Faraday's name, in the 'Philosophical Transactions.'
The second memoir was sent to the Royal Society on December 19, 1844.
I may add that while he was conducting his first experiments on the
liquefaction of gases, thirteen pieces of glass were on one occasion
driven by an explosion into Faraday's eye.

Some small notices and papers, including the observation that glass
readily changes colour in sunlight, follow here. In 1825 and 1826
Faraday published papers in the 'Philosophical Transactions' on
'new compounds of carbon and hydrogen,' and on 'sulphonaphthalic acid.'
In the former of these papers he announced the discovery of Benzol,
which, in the hands of modern chemists, has become the foundation of
our splendid aniline dyes. But he swerved incessantly from chemistry
into physics; and in 1826 we find him engaged in investigating the
limits of vaporization, and showing, by exceedingly strong and
apparently conclusive arguments, that even in the case of mercury
such a limit exists; much more he conceived it to be certain that
our atmosphere does not contain the vapour of the fixed constituents
of the earth's crust. This question, I may say, is likely to remain
an open one. Dr. Rankine, for example, has lately drawn attention
to the odour of certain metals; whence comes this odour, if it be
not from the vapour of the metal?

In 1825 Faraday became a member of a committee, to which Sir John
Herschel and Mr. Dollond also belonged, appointed by the Royal Society
to examine, and if possible improve, the manufacture of glass for
optical purposes. Their experiments continued till 1829, when the
account of them constituted the subject of a 'Bakerian Lecture.'
This lectureship, founded in 1774 by Henry Baker, Esq., of the
Strand, London, provides that every year a lecture shall be given
before the Royal Society, the sum of four pounds being paid to the
lecturer. The Bakerian Lecture, however, has long since passed from
the region of pay to that of honour, papers of mark only being
chosen for it by the council of the Society. Faraday's first
Bakerian Lecture, 'On the Manufacture of Glass for Optical Purposes,'
was delivered at the close of 1829. It is a most elaborate and
conscientious description of processes, precautions, and results:
the details were so exact and so minute, and the paper consequently
so long, that three successive sittings of the Royal Society were
taken up by the delivery of the lecture.[3] This glass did not turn
out to be of important practical use, but it happened afterwards to
be the foundation of two of Faraday's greatest discoveries.[4]

The experiments here referred to were commenced at the Falcon Glass
Works, on the premises of Messrs. Green and Pellatt, but Faraday
could not conveniently attend to them there. In 1827, therefore,
a furnace was erected in the yard of the Royal Institution; and it
was at this time, and with a view of assisting him at the furnace,
that Faraday engaged Sergeant Anderson, of the Royal Artillery,
the respectable, truthful, and altogether trustworthy man whose
appearance here is so fresh in our memories. Anderson continued to
be the reverential helper of Faraday and the faithful servant of
this Institution for nearly forty years.[5]

In 1831 Faraday published a paper, 'On a peculiar class of Optical
Deceptions,' to which I believe the beautiful optical toy called the
Chromatrope owes its origin. In the same year he published a paper
on Vibrating Surfaces, in which he solved an acoustical problem
which, though of extreme simplicity when solved, appears to have
baffled many eminent men. The problem was to account for the fact
that light bodies, such as the seed of lycopodium, collected at the
vibrating parts of sounding plates, while sand ran to the nodal
lines. Faraday showed that the light bodies were entangled in the
little whirlwinds formed in the air over the places of vibration,
and through which the heavier sand was readily projected. Faraday's
resources as an experimentalist were so wonderful, and his delight
in experiment was so great, that he sometimes almost ran into excess
in this direction. I have heard him say that this paper on
vibrating surfaces was too heavily laden with experiments.

Footnotes to Chapter 2

[1] The reader's attention is directed to the concluding paragraph
of the 'Preface to the Second Edition written in December, 1869.
Also to the Life of Faraday by Dr. Bence Jones, vol. i. p. 338 et seq.

[2] Paris: Life of Davy, p. 391.

[3] Viz., November 19, December 3 and 10.

[4] I make the following extract from a letter from Sir John Herschel,
written to me from Collingwood, on the 3rd of November, 1867:--

'I will take this opportunity to mention that I believe myself to
have originated the suggestion of the employment of borate of lead
for optical purposes. It was somewhere in the year 1822, as well as
I can recollect, that I mentioned it to Sir James (then Mr.) South;
and, in consequence, the trial was made in his laboratory in
Blackman Street, by precipitating and working a large quantity of
borate of lead, and fusing it under a muffle in a porcelain
evaporating dish. A very limpid (though slightly yellow) glass
resulted, the refractive index 1.866! (which you will find set down
in my table of refractive indices in my article "Light,"
Encyclopaedia Metropolitana). It was, however, too soft for optical
use as an object-glass. This Faraday overcame, at least to a
considerable degree, by the introduction of silica.'

[5] Regarding Anderson, Faraday writes thus in 1845:--'I cannot
resist the occasion that is thus offered to me of mentioning the
name of Mr. Anderson, who came to me as an assistant in the glass
experiments, and has remained ever since in the laboratory of the
Royal Institution. He assisted me in all the researches into which
I have entered since that time; and to his care, steadiness,
exactitude, and faithfulness in the performance of all that has been
committed to his charge, I am much indebted.--M. F.' (Exp. Researches,
vol. iii. p. 3, footnote.)

Chapter 3.

Discovery of Magneto-electricity: Explanation of Argo's magnetism of
rotation: Terrestrial magneto-electric induction: The extra current.

The work thus referred to, though sufficient of itself to secure no
mean scientific reputation, forms but the vestibule of Faraday's
achievements. He had been engaged within these walls for eighteen
years. During part of the time he had drunk in knowledge from Davy,
and during the remainder he continually exercised his capacity for
independent inquiry. In 1831 we have him at the climax of his
intellectual strength, forty years of age, stored with knowledge and
full of original power. Through reading, lecturing, and experimenting,
he had become thoroughly familiar with electrical science: he saw
where light was needed and expansion possible. The phenomena of
ordinary electric induction belonged, as it were, to the alphabet of
his knowledge: he knew that under ordinary circumstances the
presence of an electrified body was sufficient to excite, by
induction, an unelectrified body. He knew that the wire which
carried an electric current was an electrified body, and still that
all attempts had failed to make it excite in other wires a state
similar to its own.

What was the reason of this failure? Faraday never could work from
the experiments of others, however clearly described. He knew well
that from every experiment issues a kind of radiation, luminous in
different degrees to different minds, and he hardly trusted himself
to reason upon an experiment that he had not seen. In the autumn of
1831 he began to repeat the experiments with electric currents,
which, up to that time, had produced no positive result. And here,
for the sake of younger inquirers, if not for the sake of us all,
it is worth while to dwell for a moment on a power which Faraday
possessed in an extraordinary degree. He united vast strength with
perfect flexibility. His momentum was that of a river, which
combines weight and directness with the ability to yield to the
flexures of its bed. The intentness of his vision in any direction
did not apparently diminish his power of perception in other
directions; and when he attacked a subject, expecting results he had
the faculty of keeping his mind alert, so that results different
from those which he expected should not escape him through

He began his experiments 'on the induction of electric currents' by
composing a helix of two insulated wires which were wound side by
side round the same wooden cylinder. One of these wires he connected
with a voltaic battery of ten cells, and the other with a sensitive
galvanometer. When connection with the battery was made, and while
the current flowed, no effect whatever was observed at the
galvanometer. But he never accepted an experimental result, until he
had applied to it the utmost power at his command. He raised his
battery from 10 cells to 120 cells, but without avail. The current
flowed calmly through the battery wire without producing, during its
flow, any sensible result upon the galvanometer.

'During its flow,' and this was the time when an effect was expected--
but here Faraday's power of lateral vision, separating, as it were,
from the line of expectation, came into play--he noticed that a
feeble movement of the needle always occurred at the moment when he
made contact with the battery; that the needle would afterwards
return to its former position and remain quietly there unaffected by
the flowing current. At the moment, however, when the circuit was
interrupted the needle again moved, and in a direction opposed to
that observed on the completion of the circuit.

This result, and others of a similar kind, led him to the conclusion
'that the battery current through the one wire did in reality induce
a similar current through the other; but that it continued for an
instant only, and partook more of the nature of the electric wave
from a common Leyden jar than of the current from a voltaic battery.'
The momentary currents thus generated were called induced currents,
while the current which generated them was called the inducing
current. It was immediately proved that the current generated at
making the circuit was always opposed in direction to its generator,
while that developed on the rupture of the circuit coincided in
direction with the inducing current. It appeared as if the current
on its first rush through the primary wire sought a purchase in the
secondary one, and, by a kind of kick, impelled backward through the
latter an electric wave, which subsided as soon as the primary
current was fully established.

Faraday, for a time, believed that the secondary wire, though
quiescent when the primary current had been once established, was
not in its natural condition, its return to that condition being
declared by the current observed at breaking the circuit. He called
this hypothetical state of the wire the electro-tonic state: he
afterwards abandoned this hypothesis, but seemed to return to it in
later life. The term electro-tonic is also preserved by Professor
Du Bois Reymond to express a certain electric condition of the nerves,
and Professor Clerk Maxwell has ably defined and illustrated the
hypothesis in the Tenth Volume of the 'Transactions of the Cambridge
Philosophical Society.'

The mere approach of a wire forming a closed curve to a second wire
through which a voltaic current flowed was then shown by Faraday to
be sufficient to arouse in the neutral wire an induced current,
opposed in direction to the inducing current; the withdrawal of the
wire also generated a current having the same direction as the
inducing current; those currents existed only during the time of
approach or withdrawal, and when neither the primary nor the
secondary wire was in motion, no matter how close their proximity
might be, no induced current was generated.

Faraday has been called a purely inductive philosopher. A great deal
of nonsense is, I fear, uttered in this land of England about
induction and deduction. Some profess to befriend the one, some the
other, while the real vocation of an investigator, like Faraday,
consists in the incessant marriage of both. He was at this time full
of the theory of Ampere, and it cannot be doubted that numbers of
his experiments were executed merely to test his deductions from
that theory. Starting from the discovery of Oersted, the illustrious
French philosopher had shown that all the phenomena of magnetism
then known might be reduced to the mutual attractions and repulsions
of electric currents. Magnetism had been produced from electricity,
and Faraday, who all his life long entertained a strong belief in
such reciprocal actions, now attempted to effect the evolution of
electricity from magnetism. Round a welded iron ring he placed two
distinct coils of covered wire, causing the coils to occupy opposite
halves of the ring. Connecting the ends of one of the coils with a
galvanometer, he found that the moment the ring was magnetised, by
sending a current through the other coil, the galvanometer needle
whirled round four or five times in succession. The action,
as before, was that of a pulse, which vanished immediately.
On interrupting the circuit, a whirl of the needle in the opposite
direction occurred. It was only during the time of magnetization or
demagnetization that these effects were produced. The induced
currents declared a change of condition only, and they vanished the
moment the act of magnetization or demagnetization was complete.

The effects obtained with the welded ring were also obtained with
straight bars of iron. Whether the bars were magnetised by the
electric current, or were excited by the contact of permanent steel
magnets, induced currents were always generated during the rise,
and during the subsidence of the magnetism. The use of iron was then
abandoned, and the same effects were obtained by merely thrusting a
permanent steel magnet into a coil of wire. A rush of electricity
through the coil accompanied the insertion of the magnet; an equal
rush in the opposite direction accompanied its withdrawal.
The precision with which Faraday describes these results, and the
completeness with which he defines the boundaries of his facts,
are wonderful. The magnet, for example, must not be passed quite
through the coil, but only half through; for if passed wholly
through, the needle is stopped as by a blow, and then he shows how
this blow results from a reversal of the electric wave in the helix.
He next operated with the powerful permanent magnet of the Royal
Society, and obtained with it, in an exalted degree, all the
foregoing phenomena.

And now he turned the light of these discoveries upon the darkest
physical phenomenon of that day. Arago had discovered, in 1824, that
a disk of non-magnetic metal had the power of bringing a vibrating
magnetic needle suspended over it rapidly to rest; and that on
causing the disk to rotate the magnetic needle rotated along with
it. When both were quiescent, there was not the slightest measurable
attraction or repulsion exerted between the needle and the disk;
still when in motion the disk was competent to drag after it, not
only a light needle, but a heavy magnet. The question had been
probed and investigated with admirable skill both by Arago and
Ampere, and Poisson had published a theoretic memoir on the subject;
but no cause could be assigned for so extraordinary an action.
It had also been examined in this country by two celebrated men,
Mr. Babbage and Sir John Herschel; but it still remained a mystery.
Faraday always recommended the suspension of judgment in cases of
doubt. 'I have always admired,' he says, 'the prudence and
philosophical reserve shown by M. Arago in resisting the temptation
to give a theory of the effect he had discovered, so long as he
could not devise one which was perfect in its application, and in
refusing to assent to the imperfect theories of others.' Now,
however, the time for theory had come. Faraday saw mentally the
rotating disk, under the operation of the magnet, flooded with his
induced currents, and from the known laws of interaction between
currents and magnets he hoped to deduce the motion observed by
Arago. That hope he realised, showing by actual experiment that when
his disk rotated currents passed through it, their position and
direction being such as must, in accordance with the established
laws of electro-magnetic action, produce the observed rotation.

Introducing the edge of his disk between the poles of the large
horseshoe magnet of the Royal Society, and connecting the axis and
the edge of the disk, each by a wire with a galvanometer, he
obtained, when the disk was turned round, a constant flow of
electricity. The direction of the current was determined by the
direction of the motion, the current being reversed when the
rotation was reversed. He now states the law which rules the
production of currents in both disks and wires, and in so doing
uses, for the first time, a phrase which has since become famous.
When iron filings are scattered over a magnet, the particles of iron
arrange themselves in certain determinate lines called magnetic
curves. In 1831, Faraday for the first time called these curves
'lines of magnetic force'; and he showed that to produce induced
currents neither approach to nor withdrawal from a magnetic source,
or centre, or pole, was essential, but that it was only necessary to
cut appropriately the lines of magnetic force. Faraday's first paper
on Magneto-electric Induction, which I have here endeavoured to
condense, was read before the Royal Society on the 24th of November,

On January 12, 1832, he communicated to the Royal Society a second
paper on Terrestrial Magneto-electric Induction, which was chosen as
the Bakerian Lecture for the year. He placed a bar of iron in a coil
of wire, and lifting the bar into the direction of the dipping needle,
he excited by this action a current in the coil. On reversing the
bar, a current in the opposite direction rushed through the wire.
The same effect was produced when, on holding the helix in the line
of dip, a bar of iron was thrust into it. Here, however, the earth
acted on the coil through the intermediation of the bar of iron.
He abandoned the bar and simply set a copper plate spinning in a
horizontal plane; he knew that the earth's lines of magnetic force
then crossed the plate at an angle of about 70degrees. When the plate
spun round, the lines of force were intersected and induced currents
generated, which produced their proper effect when carried from the
plate to the galvanometer. 'When the plate was in the magnetic
meridian, or in any other plane coinciding with the magnetic dip,
then its rotation produced no effect upon the galvanometer.'

At the suggestion of a mind fruitful in suggestions of a profound
and philosophic character--I mean that of Sir John Herschel--
Mr. Barlow, of Woolwich, had experimented with a rotating iron shell.
Mr. Christie had also performed an elaborate series of experiments
on a rotating iron disk. Both of them had found that when in
rotation the body exercised a peculiar action upon the magnetic
needle, deflecting it in a manner which was not observed during
quiescence; but neither of them was aware at the time of the agent
which produced this extraordinary deflection. They ascribed it to
some change in the magnetism of the iron shell and disk.

But Faraday at once saw that his induced currents must come into
play here, and he immediately obtained them from an iron disk.
With a hollow brass ball, moreover, he produced the effects obtained
by Mr. Barlow. Iron was in no way necessary: the only condition of
success was that the rotating body should be of a character to admit
of the formation of currents in its substance: it must, in other
words, be a conductor of electricity. The higher the conducting
power the more copious were the currents. He now passes from his
little brass globe to the globe of the earth. He plays like a
magician with the earth's magnetism. He sees the invisible lines
along which its magnetic action is exerted, and sweeping his wand
across these lines evokes this new power. Placing a simple loop of
wire round a magnetic needle he bends its upper portion to the west:
the north pole of the needle immediately swerves to the east: he
bends his loop to the east, and the north pole moves to the west.
Suspending a common bar magnet in a vertical position, he causes it
to spin round its own axis. Its pole being connected with one end
of a galvanometer wire, and its equator with the other end,
electricity rushes round the galvanometer from the rotating magnet.
He remarks upon the 'singular independence' of the magnetism and the
body of the magnet which carries it. The steel behaves as if it
were isolated from its own magnetism.

And then his thoughts suddenly widen, and he asks himself whether
the rotating earth does not generate induced currents as it turns
round its axis from west to east. In his experiment with the
twirling magnet the galvanometer wire remained at rest; one portion
of the circuit was in motion relatively to another portion. But in
the case of the twirling planet the galvanometer wire would
necessarily be carried along with the earth; there would be no
relative motion. What must be the consequence? Take the case of a
telegraph wire with its two terminal plates dipped into the earth,
and suppose the wire to lie in the magnetic meridian. The ground
underneath the wire is influenced like the wire itself by the
earth's rotation; if a current from south to north be generated in
the wire, a similar current from south to north would be generated
in the earth under the wire; these currents would run against the
same terminal plate, and thus neutralise each other.

This inference appears inevitable, but his profound vision perceived
its possible invalidity. He saw that it was at least possible that
the difference of conducting power between the earth and the wire
might give one an advantage over the other, and that thus a residual
or differential current might be obtained. He combined wires of
different materials, and caused them to act in opposition to each
other, but found the combination ineffectual. The more copious flow
in the better conductor was exactly counterbalanced by the
resistance of the worse. Still, though experiment was thus emphatic,
he would clear his mind of all discomfort by operating on the earth
itself. He went to the round lake near Kensington Palace, and
stretched 480 feet of copper wire, north and south, over the lake,
causing plates soldered to the wire at its ends to dip into the
water. The copper wire was severed at the middle, and the severed
ends connected with a galvanometer. No effect whatever was observed.
But though quiescent water gave no effect, moving water might.
He therefore worked at London Bridge for three days during the ebb
and flow of the tide, but without any satisfactory result. Still he
urges, 'Theoretically it seems a necessary consequence, that where
water is flowing there electric currents should be formed. If a line
be imagined passing from Dover to Calais through the sea, and
returning through the land, beneath the water, to Dover, it traces
out a circuit of conducting matter one part of which, when the water
moves up or down the channel, is cutting the magnetic curves of the
earth, whilst the other is relatively at rest.... There is every
reason to believe that currents do run in the general direction of
the circuit described, either one way or the other, according as the
passage of the waters is up or down the channel.' This was written
before the submarine cable was thought of, and he once informed me
that actual observation upon that cable had been found to be in
accordance with his theoretic deduction.[1]

Three years subsequent to the publication of these researches--
that is to say, on January 29, 1835--Faraday read before the Royal
Society a paper 'On the influence by induction of an electric
current upon itself.' A shock and spark of a peculiar character had
been observed by a young man named William Jenkin, who must have
been a youth of some scientific promise, but who, as Faraday once
informed me, was dissuaded by his own father from having anything to
do with science. The investigation of the fact noticed by Mr. Jenkin
led Faraday to the discovery of the extra current, or the current
induced in the primary wire itself at the moments of making and
breaking contact, the phenomena of which he described and
illustrated in the beautiful and exhaustive paper referred to.

Seven-and-thirty years have passed since the discovery of
magneto-electricity; but, if we except the extra current, until
quite recently nothing of moment was added to the subject. Faraday
entertained the opinion that the discoverer of a great law or
principle had a right to the 'spoils'--this was his term--arising
from its illustration; and guided by the principle he had discovered,
his wonderful mind, aided by his wonderful ten fingers, overran in a
single autumn this vast domain, and hardly left behind him the shred
of a fact to be gathered by his successors.

And here the question may arise in some minds, What is the use of it
all? The answer is, that if man's intellectual nature thirsts for
knowledge, then knowledge is useful because it satisfies this
thirst. If you demand practical ends, you must, I think, expand your
definition of the term practical, and make it include all that
elevates and enlightens the intellect, as well as all that ministers
to the bodily health and comfort of men. Still, if needed, an answer
of another kind might be given to the question 'What is its use?'
As far as electricity has been applied for medical purposes, it has
been almost exclusively Faraday's electricity. You have noticed
those lines of wire which cross the streets of London. It is
Faraday's currents that speed from place to place through these
wires. Approaching the point of Dungeness, the mariner sees an
unusually brilliant light, and from the noble phares of La Heve the
same light flashes across the sea. These are Faraday's sparks
exalted by suitable machinery to sunlike splendour. At the present
moment the Board of Trade and the Brethren of the Trinity House, as
well as the Commissioners of Northern Lights, are contemplating the
introduction of the Magneto-electric Light at numerous points upon
our coasts; and future generations will be able to refer to those
guiding stars in answer to the question. What has been the practical
use of the labours of Faraday? But I would again emphatically say,
that his work needs no such justification, and that if he had
allowed his vision to be disturbed by considerations regarding the
practical use of his discoveries, those discoveries would never have
been made by him. 'I have rather,' he writes in 1831, 'been desirous
of discovering new facts and new relations dependent on
magneto-electric induction, than of exalting the force of those
already obtained; being assured that the latter would find their
full development hereafter.'

In 1817, when lecturing before a private society in London on the
element chlorine, Faraday thus expressed himself with reference to
this question of utility. 'Before leaving this subject, I will point
out the history of this substance, as an answer to those who are in
the habit of saying to every new fact. "What is its use?"
Dr. Franklin says to such, "What is the use of an infant?" The answer
of the experimentalist is, "Endeavour to make it useful." When Scheele
discovered this substance, it appeared to have no use; it was in its
infancy and useless state, but having grown up to maturity, witness
its powers, and see what endeavours to make it useful have done.'

Footnote to Chapter 3

[1] I am indebted to a friend for the following exquisite morsel:--
'A short time after the publication of Faraday's first researches in
magneto-electricity, he attended the meeting of the British
Association at Oxford, in 1832. On this occasion he was requested
by some of the authorities to repeat the celebrated experiment of
eliciting a spark from a magnet, employing for this purpose the
large magnet in the Ashmolean Museum. To this he consented, and a
large party assembled to witness the experiments, which, I need not
say, were perfectly successful. Whilst he was repeating them a
dignitary of the University entered the room, and addressing himself
to Professor Daniell, who was standing near Faraday, inquired what
was going on. The Professor explained to him as popularly as
possible this striking result of Faraday's great discovery.
The Dean listened with attention and looked earnestly at the brilliant
spark, but a moment after he assumed a serious countenance and shook
his head; "I am sorry for it," said he, as he walked away; in the
middle of the room he stopped for a moment and repeated, "I am sorry
for it:" then walking towards the door, when the handle was in his
hand he turned round and said, "Indeed I am sorry for it; it is
putting new arms into the hands of the incendiary." This occurred a
short time after the papers had been filled with the doings of the
hayrick burners. An erroneous statement of what fell from the
Dean's mouth was printed at the time in one of the Oxford papers.
He is there wrongly stated to have said, "It is putting new arms
into the hands of the infidel."'

Chapter 4.

Points of Character.

A point highly illustrative of the character of Faraday now comes into
view. He gave an account of his discovery of Magneto-electricity
in a letter to his friend M. Hachette, of Paris, who communicated
the letter to the Academy of Sciences. The letter was translated
and published; and immediately afterwards two distinguished Italian
philosophers took up the subject, made numerous experiments, and
published their results before the complete memoirs of Faraday had
met the public eye. This evidently irritated him. He reprinted the
paper of the learned Italians in the 'Philosophical Magazine,'
accompanied by sharp critical notes from himself. He also wrote a
letter dated Dec. 1, 1832, to Gay Lussac, who was then one of the
editors of the 'Annales de Chimie,' in which he analysed the results
of the Italian philosophers, pointing out their errors, and defending
himself from what he regarded as imputations on his character.
The style of this letter is unexceptionable, for Faraday could not
write otherwise than as a gentleman; but the letter shows that had he
willed it he could have hit hard. We have heard much of Faraday's
gentleness and sweetness and tenderness. It is all true, but it is
very incomplete. You cannot resolve a powerful nature into these
elements, and Faraday's character would have been less admirable
than it was had it not embraced forces and tendencies to which the
silky adjectives 'gentle' and 'tender' would by no means apply.
Underneath his sweetness and gentleness was the heat of a volcano.
He was a man of excitable and fiery nature; but through high
self-discipline he had converted the fire into a central glow and
motive power of life, instead of permitting it to waste itself in
useless passion. 'He that is slow to anger,' saith the sage,
'is greater than the mighty, and he that ruleth his own spirit than
he that taketh a city.' Faraday was not slow to anger, but he
completely ruled his own spirit, and thus, though he took no cities,
he captivated all hearts.

As already intimated, Faraday had contributed many of his minor
papers--including his first analysis of caustic lime--to the
'Quarterly Journal of Science.' In 1832, he collected those papers
and others together in a small octavo volume, labelled them, and
prefaced them thus:--

published in octavo, up to 1832.
M. Faraday.'

'Papers of mine, published in octavo, in the "Quarterly Journal of
Science," and elsewhere, since the time that Sir H. Davy encouraged
me to write the analysis of caustic lime.

'Some, I think (at this date), are good; others moderate; and some
bad. But I have put all into the volume, because of the utility
they have been of to me--and none more than the bad--in pointing out
to me in future, or rather, after times, the faults it became me to
watch and to avoid.

'As I never looked over one of my papers a year after it was written
without believing both in philosophy and manner it could have been
much better done, I still hope the collection may be of great use to

'M. Faraday.
'Aug. 18, 1832.'

'None more than the bad!' This is a bit of Faraday's innermost nature;
and as I read these words I am almost constrained to retract what I
have said regarding the fire and excitability of his character.
But is he not all the more admirable, through his ability to tone
down and subdue that fire and that excitability, so as to render
himself able to write thus as a little child? I once took the liberty
of censuring the conclusion of a letter of his to the Dean of
St. Paul's. He subscribed himself 'humbly yours,' and I objected to
the adverb. 'Well, but, Tyndall,' he said, 'I am humble; and still
it would be a great mistake to think that I am not also proud.'
This duality ran through his character. A democrat in his defiance
of all authority which unfairly limited his freedom of thought,
and still ready to stoop in reverence to all that was really worthy
of reverence, in the customs of the world or the characters of men.

And here, as well as elsewhere, may be introduced a letter which
bears upon this question of self-control, written long years
subsequent to the period at which we have now arrived. I had been
at Glasgow in 1855, at a meeting of the British Association. On a
certain day, I communicated a paper to the physical section, which
was followed by a brisk discussion. Men of great distinction took
part in it, the late Dr. Whewell among the number, and it waxed warm
on both sides. I was by no means content with this discussion; and
least of all, with my own part in it. This discontent affected me
for some days, during which I wrote to Faraday, giving him no
details, but expressing, in a general way, my dissatisfaction.
I give the following extract from his reply:--

'Sydenham, Oct. 6, 1855.

'My Dear Tyndall,--These great meetings, of which I think very well
altogether, advance science chiefly by bringing scientific men
together and making them to know and be friends with each other;
and I am sorry when that is not the effect in every part of their
course. I know nothing except from what you tell me, for I have not
yet looked at the reports of the proceedings; but let me, as an old
man, who ought by this time to have profited by experience, say that
when I was younger I found I often misinterpreted the intentions of
people, and found they did not mean what at the time I supposed they
meant; and, further, that as a general rule, it was better to be a
little dull of apprehension where phrases seemed to imply pique,
and quick in perception when, on the contrary, they seemed to imply
kindly feeling. The real truth never fails ultimately to appear;
and opposing parties, if wrong, are sooner convinced when replied to
forbearingly, than when overwhelmed. All I mean to say is, that it
is better to be blind to the results of partisanship, and quick to
see good will. One has more happiness in oneself in endeavouring to
follow the things that make for peace. You can hardly imagine how
often I have been heated in private when opposed, as I have thought,
unjustly and superciliously, and yet I have striven, and succeeded,
I hope, in keeping down replies of the like kind. And I know I have
never lost by it. I would not say all this to you did I not esteem
you as a true philosopher and friend.[1]

'Yours, very truly,
'M. Faraday.'

Footnote to Chapter 4

[1] Faraday would have been rejoiced to learn that, during its last
meeting at Dundee, the British Association illustrated in a striking
manner the function which he here describes as its principal one.
In my own case, a brotherly welcome was everywhere manifested.
In fact, the differences of really honourable and sane men are never
beyond healing.

Chapter 5.

Identity of electricities; first researches on electro-chemistry.

I have already once used the word 'discomfort' in reference to the
occasional state of Faraday's mind when experimenting. It was to
him a discomfort to reason upon data which admitted of doubt.
He hated what he called 'doubtful knowledge,' and ever tended either
to transfer it into the region of undoubtful knowledge, or of certain
and definite ignorance. Pretence of all kinds, whether in life or in
philosophy, was hateful to him. He wished to know the reality of our
nescience as well as of our science. 'Be one thing or the other,'
he seemed to say to an unproved hypothesis; 'come out as a solid truth,
or disappear as a convicted lie.' After making the great discovery
which I have attempted to describe, a doubt seemed to beset him as
regards the identity of electricities. 'Is it right,' he seemed to ask,
'to call this agency which I have discovered electricity at all?
Are there perfectly conclusive grounds for believing that the
electricity of the machine, the pile, the gymnotus and torpedo,
magneto-electricity and thermo-electricity, are merely different
manifestations of one and the same agent?' To answer this question
to his own satisfaction he formally reviewed the knowledge of that day.
He added to it new experiments of his own, and finally decided
in favour of the 'Identity of Electricities.' His paper upon this
subject was read before the Royal Society on January 10 and 17, 1833.

After he had proved to his own satisfaction the identity of
electricities, he tried to compare them quantitatively together.
The terms quantity and intensity, which Faraday constantly used,
need a word of explanation here. He might charge a single Leyden jar
by twenty turns of his machine, or he might charge a battery of ten
jars by the same number of turns. The quantity in both cases would
be sensibly the same, but the intensity of the single jar would be
the greatest, for here the electricity would be less diffused.
Faraday first satisfied himself that the needle of his galvanometer
was caused to swing through the same arc by the same quantity of
machine electricity, whether it was condensed in a small battery or
diffused over a large one. Thus the electricity developed by thirty
turns of his machine produced, under very variable conditions of
battery surface, the same deflection. Hence he inferred the
possibility of comparing, as regards quantity, electricities which
differ greatly from each other in intensity. His object now is to
compare frictional with voltaic electricity. Moistening bibulous
paper with the iodide of potassium--a favourite test of his--and
subjecting it to the action of machine electricity, he decomposed
the iodide, and formed a brown spot where the iodine was liberated.
Then he immersed two wires, one of zinc, the other of platinum, each
1/13th of an inch in diameter, to a depth of 5/8ths of an inch in
acidulated water during eight beats of his watch, or 3/20ths of a
second; and found that the needle of his galvanometer swung through
the same arc, and coloured his moistened paper to the same extent,
as thirty turns of his large electrical machine. Twenty-eight turns
of the machine produced an effect distinctly less than that produced
by his two wires. Now, the quantity of water decomposed by the
wires in this experiment totally eluded observation; it was
immeasurably small; and still that amount of decomposition involved
the development of a quantity of electric force which, if applied in
a proper form, would kill a rat, and no man would like to bear it.

In his subsequent researches 'On the absolute Quantity of
Electricity associated with the Particles or Atoms of matter,'
he endeavours to give an idea of the amount of electrical force
involved in the decomposition of a single grain of water. He is
almost afraid to mention it, for he estimates it at 800,000
discharges of his large Leyden battery. This, if concentrated in a
single discharge, would be equal to a very great flash of lightning;
while the chemical action of a single grain of water on four grains
of zinc would yield electricity equal in quantity to a powerful
thunderstorm. Thus his mind rises from the minute to the vast,
expanding involuntarily from the smallest laboratory fact till it
embraces the largest and grandest natural phenomena.[1]

In reality, however, he is at this time only clearing his way,
and he continues laboriously to clear it for some time afterwards.
He is digging the shaft, guided by that instinct towards the mineral
lode which was to him a rod of divination. 'Er riecht die Wahrheit,'
said the lamented Kohlrausch, an eminent German, once in my hearing:--
'He smells the truth.' His eyes are now steadily fixed on this
wonderful voltaic current, and he must learn more of its mode of

On May 23, 1833, he read a paper before the Royal Society 'On a new
Law of Electric Conduction.' He found that, though the current
passed through water, it did not pass through ice:--why not, since
they are one and the same substance? Some years subsequently he
answered this question by saying that the liquid condition enables
the molecule of water to turn round so as to place itself in the
proper line of polarization, while the rigidity of the solid
condition prevents this arrangement. This polar arrangement must
precede decomposition, and decomposition is an accompaniment of
conduction. He then passed on to other substances; to oxides and
chlorides, and iodides, and salts, and sulphurets, and found them
all insulators when solid, and conductors when fused. In all cases,
moreover, except one--and this exception he thought might be
apparent only--he found the passage of the current across the fused
compound to be accompanied by its decomposition. Is then the act of
decomposition essential to the act of conduction in these bodies?
Even recently this question was warmly contested. Faraday was very
cautious latterly in expressing himself upon this subject; but as a
matter of fact he held that an infinitesimal quantity of electricity
might pass through a compound liquid without producing its
decomposition. De la Rive, who has been a great worker on the
chemical phenomena of the pile, is very emphatic on the other side.
Experiment, according to him and others, establishes in the most
conclusive manner that no trace of electricity can pass through a
liquid compound without producing its equivalent decomposition.[2]

Faraday has now got fairly entangled amid the chemical phenomena of
the pile, and here his previous training under Davy must have been
of the most important service to him. Why, he asks, should
decomposition thus take place?--what force is it that wrenches the
locked constituents of these compounds asunder? On the 20th of June,
1833, he read a paper before the Royal Society 'On Electro-chemical
Decomposition,' in which he seeks to answer these questions.
The notion had been entertained that the poles, as they are called,
of the decomposing cell, or in other words the surfaces by which the
current enters and quits the liquid, exercised electric attractions
upon the constituents of the liquid and tore them asunder. Faraday
combats this notion with extreme vigour. Litmus reveals, as you
know, the action of an acid by turning red, turmeric reveals the
action of an alkali by turning brown. Sulphate of soda, you know,
is a salt compounded of the alkali soda and sulphuric acid.
The voltaic current passing through a solution of this salt so
decomposes it, that sulphuric acid appears at one pole of the
decomposing cell and alkali at the other. Faraday steeped a piece
of litmus paper and a piece of turmeric paper in a solution of
sulphate of soda: placing each of them upon a separate plate of
glass, he connected them together by means of a string moistened
with the same solution. He then attached one of them to the
positive conductor of an electric machine, and the other to the
gas-pipes of this building. These he called his 'discharging train.'
On turning the machine the electricity passed from paper to paper
through the string, which might be varied in length from a few
inches to seventy feet without changing the result. The first paper
was reddened, declaring the presence of sulphuric acid; the second
was browned, declaring the presence of the alkali soda.
The dissolved salt, therefore, arranged in this fashion, was decomposed
by the machine, exactly as it would have been by the voltaic
current. When instead of using the positive conductor he used the
negative, the positions of the acid and alkali were reversed.
Thus he satisfied himself that chemical decomposition by the machine
is obedient to the laws which rule decomposition by the pile.

And now he gradually abolishes those so-called poles, to the
attraction of which electric decomposition had been ascribed.
He connected a piece of turmeric paper moistened with the sulphate
of soda with the positive conductor of his machine; then he placed a
metallic point in connection with his discharging train opposite the
moist paper, so that the electricity should discharge through the
air towards the point. The turning of the machine caused the
corners of the piece of turmeric paper opposite to the point to turn
brown, thus declaring the presence of alkali. He changed the
turmeric for litmus paper, and placed it, not in connection with his
conductor, but with his discharging train, a metallic point
connected with the conductor being fixed at a couple of inches from
the paper; on turning the machine, acid was liberated at the edges
and corners of the litmus. He then placed a series of pointed
pieces of paper, each separate piece being composed of two halves,
one of litmus and the other of turmeric paper, and all moistened
with sulphate of soda, in the line of the current from the machine.
The pieces of paper were separated from each other by spaces of air.
The machine was turned; and it was always found that at the point
where the electricity entered the paper, litmus was reddened, and at
the point where it quitted the paper, turmeric was browned. 'Here,'
he urges, 'the poles are entirely abandoned, but we have still
electrochemical decomposition.' It is evident to him that instead of
being attracted by the poles, the bodies separated are ejected by
the current. The effects thus obtained with poles of air he also
succeeded in obtaining with poles of water. The advance in
Faraday's own ideas made at this time is indicated by the word
'ejected.' He afterwards reiterates this view: the evolved
substances are expelled from the decomposing body, and 'not drawn
out by an attraction.

Having abolished this idea of polar attraction, he proceeds to
enunciate and develop a theory of his own. He refers to Davy's
celebrated Bakerian Lecture, given in 1806, which he says 'is almost
entirely occupied in the consideration of electrochemical
decompositions.' The facts recorded in that lecture Faraday regards
as of the utmost value. But 'the mode of action by which the
effects take place is stated very generally; so generally, indeed,
that probably a dozen precise schemes of electrochemical action
might be drawn up, differing essentially from each other, yet all
agreeing with the statement there given.'

It appears to me that these words might with justice be applied to
Faraday's own researches at this time. They furnish us with results
of permanent value; but little help can be found in the theory
advanced to account for them. It would, perhaps, be more correct to
say that the theory itself is hardly presentable in any tangible
form to the intellect. Faraday looks, and rightly looks, into the
heart of the decomposing body itself; he sees, and rightly sees,
active within it the forces which produce the decomposition, and he
rejects, and rightly rejects, the notion of external attraction;
but beyond the hypothesis of decompositions and recompositions,
enunciated and developed by Grothuss and Davy, he does not, I think,
help us to any definite conception as to how the force reaches the
decomposing mass and acts within it. Nor, indeed, can this be done,
until we know the true physical process which underlies what we call
an electric current.

Faraday conceives of that current as 'an axis of power having
contrary forces exactly equal in amount in opposite directions';
but this definition, though much quoted and circulated, teaches us
nothing regarding the current. An 'axis' here can only mean a
direction; and what we want to be able to conceive of is, not the
axis along which the power acts, but the nature and mode of action
of the power itself. He objects to the vagueness of De la Rive;
but the fact is, that both he and De la Rive labour under the same
difficulty. Neither wishes to commit himself to the notion of a
current compounded of two electricities flowing in two opposite
directions: but the time had not come, nor is it yet come, for the
displacement of this provisional fiction by the true mechanical
conception. Still, however indistinct the theoretic notions of
Faraday at this time may be, the facts which are rising before him
and around him are leading him gradually, but surely, to results of
incalculable importance in relation to the philosophy of the voltaic

He had always some great object of research in view, but in the
pursuit of it he frequently alighted on facts of collateral interest,
to examine which he sometimes turned aside from his direct course.
Thus we find the series of his researches on electrochemical
decomposition interrupted by an inquiry into 'the power of metals
and other solids, to induce the combination of gaseous bodies.' This
inquiry, which was received by the Royal Society on Nov. 30, 1833,
though not so important as those which precede and follow it,
illustrates throughout his strength as an experimenter. The power
of spongy platinum to cause the combination of oxygen and hydrogen
had been discovered by Dobereiner in 1823, and had been applied by
him in the construction of his well-known philosophic lamp. It was
shown subsequently by Dulong and Thenard that even a platinum wire,
when perfectly cleansed, may be raised to incandescence by its
action on a jet of cold hydrogen.

In his experiments on the decomposition of water, Faraday found that
the positive platinum plate of the decomposing cell possessed in an
extraordinary degree the power of causing oxygen and hydrogen to
combine. He traced the cause of this to the perfect cleanness of
the positive plate. Against it was liberated oxygen, which, with the
powerful affinity of the 'nascent state,' swept away all impurity
from the surface against which it was liberated. The bubbles of gas
liberated on one of the platinum plates or wires of a decomposing
cell are always much smaller, and they rise in much more rapid
succession than those from the other. Knowing that oxygen is
sixteen times heavier than hydrogen, I have more than once concluded,
and, I fear, led others into the error of concluding, that the smaller
and more quickly rising bubbles must belong to the lighter gas.
The thing appeared so obvious that I did not give myself the trouble
of looking at the battery, which would at once have told me the nature
of the gas. But Faraday would never have been satisfied with a
deduction if he could have reduced it to a fact. And he has taught
me that the fact here is the direct reverse of what I supposed it to
be. The small bubbles are oxygen, and their smallness is due to the
perfect cleanness of the surface on which they are liberated.
The hydrogen adhering to the other electrode swells into large bubbles,
which rise in much slower succession; but when the current is reversed,
the hydrogen is liberated upon the cleansed wire, and then its bubbles
also become small.

Footnotes to Chapter 5

[1] Buff finds the quantity of electricity associated with one
milligramme of hydrogen in water to be equal to 45,480 charges of a
Leyden jar, with a height of 480 millimetres, and a diameter of 160
millimetres. Weber and Kohlrausch have calculated that, if the
quantity of electricity associated with one milligramme of hydrogen
in water were diffused over a cloud at a height of 1000 metres above
the earth, it would exert upon an equal quantity of the opposite
electricity at the earth's surface an attractive force of 2,268,000
kilogrammes. (Electrolytische Maasbestimmungen, 1856, p. 262.)

[2] Faraday, sa Vie et ses Travaux, p. 20.

Chapter 6.

Laws of electro-chemical decomposition.

In our conceptions and reasonings regarding the forces of nature,
we perpetually make use of symbols which, when they possess a high
representative value, we dignify with the name of theories. Thus,
prompted by certain analogies, we ascribe electrical phenomena to
the action of a peculiar fluid, sometimes flowing, sometimes at
rest. Such conceptions have their advantages and their
disadvantages; they afford peaceful lodging to the intellect for a
time, but they also circumscribe it, and by-and-by, when the mind
has grown too large for its lodging, it often finds difficulty in
breaking down the walls of what has become its prison instead of its

No man ever felt this tyranny of symbols more deeply than Faraday,
and no man was ever more assiduous than he to liberate himself from
them, and the terms which suggested them. Calling Dr. Whewell to
his aid in 1833, he endeavoured to displace by others all terms
tainted by a foregone conclusion. His paper on Electro-chemical
Decomposition, received by the Royal Society on January 9, 1834,
opens with the proposal of a new terminology. He would avoid the
word 'current' if he could.[2] He does abandon the word 'poles' as
applied to the ends of a decomposing cell, because it suggests the
idea of attraction, substituting for it the perfectly natural term
Electrodes. He applied the term Electrolyte to every substance
which can be decomposed by the current, and the act of decomposition
he called Electrolysis. All these terms have become current in
science. He called the positive electrode the Anode, and the
negative one the Cathode, but these terms, though frequently used,
have not enjoyed the same currency as the others. The terms Anion
and Cation, which he applied to the constituents of the decomposed
electrolyte, and the term Ion, which included both anions and
cations, are still less frequently employed.

Faraday now passes from terminology to research; he sees the
necessity of quantitative determinations, and seeks to supply
himself with a measure of voltaic electricity. This he finds in the
quantity of water decomposed by the current. He tests this measure
in all possible ways, to assure himself that no error can arise from
its employment. He places in the course of one and the same current
a series of cells with electrodes of different sizes, some of them
plates of platinum, others merely platinum wires, and collects the
gas liberated on each distinct pair of electrodes. He finds the
quantity of gas to be the same for all. Thus he concludes that when
the same quantity of electricity is caused to pass through a series
of cells containing acidulated water, the electro-chemical action is
independent of the size of the electrodes.[3] He next proves that
variations in intensity do not interfere with this equality of
action. Whether his battery is charged with strong acid or with
weak; whether it consists of five pairs or of fifty pairs; in short,
whatever be its source, when the same current is sent through his
series of cells the same amount of decomposition takes place in all.
He next assures himself that the strength or weakness of his dilute
acid does not interfere with this law. Sending the same current
through a series of cells containing mixtures of sulphuric acid and
water of different strengths, he finds, however the proportion of
acid to water might vary, the same amount of gas to be collected in
all the cells. A crowd of facts of this character forced upon
Faraday's mind the conclusion that the amount of electro-chemical
decomposition depends, not upon the size of the electrodes, not upon
the intensity of the current, not upon the strength of the solution,
but solely upon the quantity of electricity which passes through the
cell. The quantity of electricity he concludes is proportional to
the amount of chemical action. On this law Faraday based the
construction of his celebrated Voltameter, or Measure of Voltaic

But before he can apply this measure he must clear his ground of
numerous possible sources of error. The decomposition of his
acidulated water is certainly a direct result of the current; but as
the varied and important researches of MM. Becquerel, De la Rive,
and others had shown, there are also secondary actions which may
materially interfere with and complicate the pure action of the
current. These actions may occur in two ways: either the liberated
ion may seize upon the electrode against which it is set free,
forming a chemical compound with that electrode; or it may seize
upon the substance of the electrolyte itself, and thus introduce
into the circuit chemical actions over and above those due to the
current. Faraday subjected these secondary actions to an exhaustive
examination. Instructed by his experiments, and rendered competent
by them to distinguish between primary and secondary results, he
proceeds to establish the doctrine of 'Definite Electro-chemical

Into the same circuit he introduced his voltameter, which consisted
of a graduated tube filled with acidulated water and provided with
platinum plates for the decomposition of the water, and also a cell
containing chloride of tin. Experiments already referred to had
taught him that this substance, though an insulator when solid, is a
conductor when fused, the passage of the current being always
accompanied by the decomposition of the chloride. He wished to
ascertain what relation this decomposition bore to that of the water
in his voltameter.

Completing his circuit, he permitted the current to continue until
'a reasonable quantity of gas' was collected in the voltameter. The
circuit was then broken, and the quantity of tin liberated compared
with the quantity of gas. The weight of the former was 3.2 grains,
that of the latter 0.49742 of a grain. Oxygen, as you know, unites
with hydrogen in the proportion of 8 to 1, to form water. Calling
the equivalent, or as it is sometimes called, the atomic weight of
hydrogen 1, that of oxygen is 8; that of water is consequently 8 + 1
or 9. Now if the quantity of water decomposed in Faraday's
experiment be represented by the number 9, or in other words by the
equivalent of water, then the quantity of tin liberated from the
fused chloride is found by an easy calculation to be 57.9, which is
almost exactly the chemical equivalent of tin. Thus both the water
and the chloride were broken up in proportions expressed by their
respective equivalents. The amount of electric force which wrenched
asunder the constituents of the molecule of water was competent,
and neither more nor less than competent, to wrench asunder the
constituents of the molecules of the chloride of tin. The fact is
typical. With the indications of his voltameter he compared the
decompositions of other substances, both singly and in series.
He submitted his conclusions to numberless tests. He purposely
introduced secondary actions. He endeavoured to hamper the
fulfilment of those laws which it was the intense desire of his mind
to see established. But from all these difficulties emerged the
golden truth, that under every variety of circumstances the
decompositions of the voltaic current are as definite in their
character as those chemical combinations which gave birth to the
atomic theory. This law of Electro-chemical Decomposition ranks,
in point of importance, with that of Definite Combining Proportions
in chemistry.

Footnotes to Chapter 6

[1] I copy these words from the printed abstract of a Friday
evening lecture, given by myself, because they remind me of
Faraday's voice, responding to the utterance by an emphatic 'hear!
hear!'--Proceedings of the Royal Institution, vol. ii. p. 132.

[2] In 1838 he expresses himself thus:--'The word current is so
expressive in common language that when applied in the consideration
of electrical phenomena, we can hardly divest it sufficiently of its
meaning, or prevent our minds from being prejudiced by it.'--
Exp. Resear., vol. i. p. 515. ($ 1617.)

[3] This conclusion needs qualification. Faraday overlooked the
part played by ozone.

Chapter 7.

Origin of power in the voltaic pile.

In one of the public areas of the town of Como stands a statue with
no inscription on its pedestal, save that of a single name, 'Volta.'
The bearer of that name occupies a place for ever memorable in the
history of science. To him we owe the discovery of the voltaic pile,
to which for a brief interval we must now turn our attention.

The objects of scientific thought being the passionless laws and
phenomena of external nature, one might suppose that their
investigation and discussion would be completely withdrawn from the
region of the feelings, and pursued by the cold dry light of the
intellect alone. This, however, is not always the case.
Man carries his heart with him into all his works. You cannot
separate the moral and emotional from the intellectual; and thus it
is that the discussion of a point of science may rise to the heat of
a battle-field. The fight between the rival optical theories of
Emission and Undulation was of this fierce character; and scarcely
less fierce for many years was the contest as to the origin and
maintenance of the power of the voltaic pile. Volta himself supposed
it to reside in the Contact of different metals. Here was exerted
his 'Electro-motive force,' which tore the combined electricities
asunder and drove them as currents in opposite directions.
To render the circulation of the current possible, it was necessary
to connect the metals by a moist conductor; for when any two metals
were connected by a third, their relation to each other was such
that a complete neutralisation of the electric motion was the result.
Volta's theory of metallic contact was so clear, so beautiful, and
apparently so complete, that the best intellects of Europe accepted
it as the expression of natural law.

Volta himself knew nothing of the chemical phenomena of the pile;
but as soon as these became known, suggestions and intimations
appeared that chemical action, and not metallic contact, might be
the real source of voltaic electricity. This idea was expressed by
Fabroni in Italy, and by Wollaston in England. It was developed and
maintained by those 'admirable electricians,' Becquerel, of Paris,
and De la Rive, of Geneva. The Contact Theory, on the other hand,
received its chief development and illustration in Germany.
It was long the scientific creed of the great chemists and natural
philosophers of that country, and to the present hour there may be
some of them unable to liberate themselves from the fascination of
their first-love.

After the researches which I have endeavoured to place before you,
it was impossible for Faraday to avoid taking a side in this
controversy. He did so in a paper 'On the Electricity of the
Voltaic Pile,' received by the Royal Society on the 7th of April,
1834. His position in the controversy might have been predicted.
He saw chemical effects going hand in hand with electrical effects,
the one being proportional to the other; and, in the paper now
before us, he proved that when the former was excluded, the latter
were sought for in vain. He produced a current without metallic
contact; he discovered liquids which, though competent to transmit
the feeblest currents--competent therefore to allow the electricity
of contact to flow through them if it were able to form a
current--were absolutely powerless when chemically inactive.

One of the very few experimental mistakes of Faraday occurred in
this investigation. He thought that with a single voltaic cell he
had obtained the spark before the metals touched, but he
subsequently discovered his error. To enable the voltaic spark to
pass through air before the terminals of the battery were united, it
was necessary to exalt the electro-motive force of the battery by
multiplying its elements; but all the elements Faraday possessed
were unequal to the task of urging the spark across the shortest
measurable space of air. Nor, indeed, could the action of the
battery, the different metals of which were in contact with each
other, decide the point in question. Still, as regards the identity
of electricities from various sources, it was at that day of great
importance to determine whether or not the voltaic current could
jump, as a spark, across an interval before contact. Faraday's
friend, Mr. Gassiot, solved this problem. He erected a battery of
4000 cells, and with it urged a stream of sparks from terminal to
terminal, when separated from each other by a measurable space of air.

The memoir on the 'Electricity of the Voltaic Pile,' published in
1834, appears to have produced but little impression upon the
supporters of the contact theory. These indeed were men of too
great intellectual weight and insight lightly to take up, or lightly
to abandon a theory. Faraday therefore resumed the attack in a
paper, communicated to the Royal Society on the 6th of February,
1840. In this paper he hampered his antagonists by a crowd of
adverse experiments. He hung difficulty after difficulty about the
neck of the contact theory, until in its efforts to escape from his
assaults it so changed its character as to become a thing totally
different from the theory proposed by Volta. The more persistently
it was defended, however, the more clearly did it show itself to be
a congeries of devices, bearing the stamp of dialectic skill rather
than of natural truth.

In conclusion, Faraday brought to bear upon it an argument which,
had its full weight and purport been understood at the time, would
have instantly decided the controversy. 'The contact theory,'
he urged, 'assumed that a force which is able to overcome powerful
resistance, as for instance that of the conductors, good or bad,
through which the current passes, and that again of the electrolytic
action where bodies are decomposed by it, can arise out of nothing;
that, without any change in the acting matter, or the consumption of
any generating force, a current shall be produced which shall go on
for ever against a constant resistance, or only be stopped, as in
the voltaic trough, by the ruins which its exertion has heaped up in
its own course. This would indeed be a creation of power, and is
like no other force in nature. We have many processes by which the
form of the power may be so changed, that an apparent conversion of
one into the other takes place. So we can change chemical force
into the electric current, or the current into chemical force.
The beautiful experiments of Seebeck and Peltier show the convertibility
of heat and electricity; and others by Oersted and myself show the
convertibility of electricity and magnetism. But in no case, not
even in those of the Gymnotus and Torpedo, is there a pure creation
or a production of power without a corresponding exhaustion of
something to supply it.'

These words were published more than two years before either Mayer
printed his brief but celebrated essay on the Forces of Inorganic
Nature, or Mr. Joule published his first famous experiments on the
Mechanical Value of Heat. They illustrate the fact that before any
great scientific principle receives distinct enunciation by
individuals, it dwells more or less clearly in the general
scientific mind. The intellectual plateau is already high, and our
discoverers are those who, like peaks above the plateau, rise a
little above the general level of thought at the time.

But many years prior even to the foregoing utterance of Faraday,
a similar argument had been employed. I quote here with equal
pleasure and admiration the following passage written by Dr. Roget
so far back as 1829. Speaking of the contact theory, he says:--
'If there could exist a power having the property ascribed to it by
the hypothesis, namely, that of giving continual impulse to a fluid
in one constant direction, without being exhausted by its own
action, it would differ essentially from all the known powers in
nature. All the powers and sources of motion with the operation of
which we are acquainted, when producing these peculiar effects, are
expended in the same proportion as those effects are produced; and
hence arises the impossibility of obtaining by their agency a
perpetual effect; or in other words a perpetual motion. But the
electro-motive force, ascribed by Volta to the metals, when in
contact, is a force which, as long as a free course is allowed to
the electricity it sets in motion, is never expended, and continues
to be excited with undiminished power in the production of a
never-ceasing effect. Against the truth of such a supposition the
probabilities are all but infinite.' When this argument, which he
employed independently, had clearly fixed itself in his mind,
Faraday never cared to experiment further on the source of
electricity in the voltaic pile. The argument appeared to him
'to remove the foundation itself of the contact theory,' and he
afterwards let it crumble down in peace.[1]

Footnote to Chapter 7

[1] To account for the electric current, which was really the core
of the whole discussion, Faraday demonstrated the impotence of the
Contact Theory as then enunciated and defended. Still, it is
certain that two different metals, when brought into contact, charge
themselves, the one with positive and the other with negative
electricity. I had the pleasure of going over this ground with
Kohlrausch in 1849, and his experiments left no doubt upon my mind
that the contact electricity of Volta was a reality, though it could
produce no current. With one of the beautiful instruments devised
by himself, Sir William Thomson has rendered this point capable of
sure and easy demonstration; and he and others now hold what may be
called a contact theory, which, while it takes into account the
action of the metals, also embraces the chemical phenomena of the
circuit. Helmholtz, I believe, was the first to give the contact
theory this new form, in his celebrated essay, Ueber die Erhaltung
der Kraft, p. 45.

Chapter 8.

Researches on frictional electricity: induction: conduction:
specific inductive capacity: theory of contiguous particles.

The burst of power which had filled the four preceding years with an
amount of experimental work unparalleled in the history of science
partially subsided in 1835, and the only scientific paper contributed
by Faraday in that year was a comparatively unimportant one, 'On an
improved Form of the Voltaic Battery.' He brooded for a time: his
experiments on electrolysis had long filled his mind; he looked, as
already stated, into the very heart of the electrolyte, endeavouring
to render the play of its atoms visible to his mental eye. He had
no doubt that in this case what is called 'the electric current' was
propagated from particle to particle of the electrolyte; he accepted
the doctrine of decomposition and recomposition which, according to
Grothuss and Davy, ran from electrode to electrode. And the thought
impressed him more and more that ordinary electric induction was
also transmitted and sustained by the action of 'contiguous

His first great paper on frictional electricity was sent to the
Royal Society on November 30, 1837. We here find him face to face
with an idea which beset his mind throughout his whole subsequent
life,--the idea of action at a distance. It perplexed and
bewildered him. In his attempts to get rid of this perplexity, he
was often unconsciously rebelling against the limitations of the
intellect itself. He loved to quote Newton upon this point; over
and over again he introduces his memorable words, 'That gravity
should be innate, inherent, and essential to matter, so that one
body may act upon another at a distance through a vacuum and without
the mediation of anything else, by and through which this action and
force may be conveyed from one to another, is to me so great an
absurdity, that I believe no man who has in philosophical matters a
competent faculty of thinking, can ever fall into it. Gravity must
be caused by an agent acting constantly according to certain laws;
but whether this agent be material or immaterial, I have left to the
consideration of my readers.'[1]

Faraday does not see the same difficulty in his contiguous particles.
And yet, by transferring the conception from masses to particles,
we simply lessen size and distance, but we do not alter the quality
of the conception. Whatever difficulty the mind experiences in
conceiving of action at sensible distances, besets it also when it
attempts to conceive of action at insensible distances. Still the
investigation of the point whether electric and magnetic effects
were wrought out through the intervention of contiguous particles or
not, had a physical interest altogether apart from the metaphysical
difficulty. Faraday grapples with the subject experimentally.
By simple intuition he sees that action at a distance must be exerted
in straight lines. Gravity, he knows, will not turn a corner, but
exerts its pull along a right line; hence his aim and effort to
ascertain whether electric action ever takes place in curved lines.
This once proved, it would follow that the action is carried on by
means of a medium surrounding the electrified bodies. His experiments
in 1837 reduced, in his opinion, this point of demonstration.
He then found that he could electrify, by induction, an insulated
sphere placed completely in the shadow of a body which screened it
from direct action. He pictured the lines of electric force bending
round the edges of the screen, and reuniting on the other side of it;
and he proved that in many cases the augmentation of the distance
between his insulated sphere and the inducing body, instead of
lessening, increased the charge of the sphere. This he ascribed to
the coalescence of the lines of electric force at some distance
behind the screen.

Faraday's theoretic views on this subject have not received general
acceptance, but they drove him to experiment, and experiment with
him was always prolific of results. By suitable arrangements he
placed a metallic sphere in the middle of a large hollow sphere,
leaving a space of something more than half an inch between them.
The interior sphere was insulated, the external one uninsulated.
To the former he communicated a definite charge of electricity.
It acted by induction upon the concave surface of the latter, and he
examined how this act of induction was effected by placing insulators
of various kinds between the two spheres. He tried gases, liquids,
and solids, but the solids alone gave him positive results.
He constructed two instruments of the foregoing description, equal in
size and similar in form. The interior sphere of each communicated
with the external air by a brass stem ending in a knob.
The apparatus was virtually a Leyden jar, the two coatings of which
were the two spheres, with a thick and variable insulator between
them. The amount of charge in each jar was determined by bringing a
proof-plane into contact with its knob and measuring by a torsion
balance the charge taken away. He first charged one of his
instruments, and then dividing the charge with the other, found that
when air intervened in both cases the charge was equally divided.
But when shellac, sulphur, or spermaceti was interposed between the
two spheres of one jar, while air occupied this interval in the
other, then he found that the instrument occupied by the 'solid
dielectric' takes more than half the original charge. A portion of
the charge was absorbed by the dielectric itself. The electricity
took time to penetrate the dielectric. Immediately after the
discharge of the apparatus, no trace of electricity was found upon
its knob. But after a time electricity was found there, the charge
having gradually returned from the dielectric in which it had been
lodged. Different insulators possess this power of permitting the
charge to enter them in different degrees. Faraday figured their
particles as polarized, and he concluded that the force of induction
is propagated from particle to particle of the dielectric from the
inner sphere to the outer one. This power of propagation possessed
by insulators he called their 'Specific Inductive Capacity.'

Faraday visualizes with the utmost clearness the state of his
contiguous particles; one after another they become charged, each
succeeding particle depending for its charge upon its predecessor.
And now he seeks to break down the wall of partition between
conductors and insulators. 'Can we not,' he says, 'by a gradual
chain of association carry up discharge from its occurrence in air
through spermaceti and water, to solutions, and then on to chlorides,
oxides, and metals, without any essential change in its character?'
Even copper, he urges, offers a resistance to the transmission of
electricity. The action of its particles differs from those of an
insulator only in degree. They are charged like the particles of
the insulator, but they discharge with greater ease and rapidity;
and this rapidity of molecular discharge is what we call conduction.
Conduction then is always preceded by atomic induction; and when,
through some quality of the body which Faraday does not define, the
atomic discharge is rendered slow and difficult, conduction passes
into insulation.

Though they are often obscure, a fine vein of philosophic thought
runs through those investigations. The mind of the philosopher
dwells amid those agencies which underlie the visible phenomena of
Induction and Conduction; and he tries by the strong light of his
imagination to see the very molecules of his dielectrics. It would,
however, be easy to criticise these researches, easy to show the
looseness, and sometimes the inaccuracy, of the phraseology
employed; but this critical spirit will get little good out of
Faraday. Rather let those who ponder his works seek to realise the
object he set before him, not permitting his occasional vagueness to
interfere with their appreciation of his speculations. We may see
the ripples, and eddies, and vortices of a flowing stream, without
being able to resolve all these motions into their constituent
elements; and so it sometimes strikes me that Faraday clearly saw
the play of fluids and ethers and atoms, though his previous
training did not enable him to resolve what he saw into its
constituents, or describe it in a manner satisfactory to a mind
versed in mechanics. And then again occur, I confess, dark sayings,
difficult to be understood, which disturb my confidence in this
conclusion. It must, however, always be remembered that he works at
the very boundaries of our knowledge, and that his mind habitually
dwells in the 'boundless contiguity of shade' by which that
knowledge is surrounded.

In the researches now under review the ratio of speculation and
reasoning to experiment is far higher than in any of Faraday's
previous works. Amid much that is entangled and dark we have
flashes of wondrous insight and utterances which seem less the
product of reasoning than of revelation. I will confine myself here
to one example of this divining power. By his most ingenious device
of a rapidly rotating mirror, Wheatstone had proved that electricity
required time to pass through a wire, the current reaching the
middle of the wire later than its two ends. 'If,' says Faraday,
'the two ends of the wire in Professor Wheatstone's experiments were
immediately connected with two large insulated metallic surfaces
exposed to the air, so that the primary act of induction, after
making the contact for discharge, might be in part removed from the
internal portion of the wire at the first instance, and disposed for
the moment on its surface jointly with the air and surrounding
conductors, then I venture to anticipate that the middle spark would
be more retarded than before. And if those two plates were the
inner and outer coatings of a large jar or Leyden battery, then the
retardation of the spark would be much greater.' This was only a
prediction, for the experiment was not made.[2] Sixteen years
subsequently, however, the proper conditions came into play, and
Faraday was able to show that the observations of Werner Siemens,
and Latimer Clark, on subterraneous and submarine wires were
illustrations, on a grand scale, of the principle which he had
enunciated in 1838. The wires and the surrounding water act as a
Leyden jar, and the retardation of the current predicted by Faraday
manifests itself in every message sent by such cables.

The meaning of Faraday in these memoirs on Induction and Conduction
is, as I have said, by no means always clear; and the difficulty
will be most felt by those who are best trained in ordinary
theoretic conceptions. He does not know the reader's needs, and he
therefore does not meet them. For instance he speaks over and over
again of the impossibility of charging a body with one electricity,
though the impossibility is by no means evident. The key to the
difficulty is this. He looks upon every insulated conductor as the
inner coating of a Leyden jar. An insulated sphere in the middle of
a room is to his mind such a coating; the walls are the outer coating,
while the air between both is the insulator, across which the charge
acts by induction. Without this reaction of the walls upon the
sphere you could no more, according to Faraday, charge it with
electricity than you could charge a Leyden jar, if its outer coating
were removed. Distance with him is immaterial. His strength as a
generalizer enables him to dissolve the idea of magnitude; and if
you abolish the walls of the room--even the earth itself--he would
make the sun and planets the outer coating of his jar. I dare not
contend that Faraday in these memoirs made all his theoretic
positions good. But a pure vein of philosophy runs through these
writings; while his experiments and reasonings on the forms and
phenomena of electrical discharge are of imperishable importance.

Footnotes to Chapter 8

[1] Newton's third letter to Bentley.

[2] Had Sir Charles Wheatstone been induced to resume his measurements,
varying the substances through which, and the conditions under which,
the current is propagated, he might have rendered great service to
science, both theoretic and experimental.

Chapter 9.

Rest needed--visit to Switzerland.

The last of these memoirs was dated from the Royal Institution in
June, 1838. It concludes the first volume of his 'Experimental
Researches on Electricity.' In 1840, as already stated, he made his
final assault on the Contact Theory, from which it never recovered.[1]
He was now feeling the effects of the mental strain to which he had
been subjected for so many years. During these years he repeatedly
broke down. His wife alone witnessed the extent of his prostration,
and to her loving care we, and the world, are indebted for the
enjoyment of his presence here so long. He found occasional relief
in a theatre. He frequently quitted London and went to Brighton and
elsewhere, always choosing a situation which commanded a view of the
sea, or of some other pleasant horizon, where he could sit and gaze
and feel the gradual revival of the faith that

'Nature never did betray
The heart that loved her.'

But very often for some days after his removal to the country, he
would be unable to do more than sit at a window and look out upon
the sea and sky.

In 1841, his state became more serious than it had ever been before.
A published letter to Mr. Richard Taylor, dated March 11, 1843,
contains an allusion to his previous condition. 'You are aware,'
he says, 'that considerations regarding health have prevented me
from working or reading on science for the last two years.' This,
at one period or another of their lives, seems to be the fate of
most great investigators. They do not know the limits of their
constitutional strength until they have transgressed them. It is,
perhaps, right that they should transgress them, in order to
ascertain where they lie. Faraday, however, though he went far
towards it, did not push his transgression beyond his power of
restitution. In 1841 Mrs. Faraday and he went to Switzerland, under
the affectionate charge of her brother, Mr. George Barnard, the artist.
This time of suffering throws fresh light upon his character.
I have said that sweetness and gentleness were not its only
constituents; that he was also fiery and strong. At the time now
referred to, his fire was low and his strength distilled away; but
the residue of his life was neither irritability nor discontent.
He was unfit to mingle in society, for conversation was a pain to him;
but let us observe the great Man-child when alone. He is at the
village of Interlaken, enjoying Jungfrau sunsets, and at times
watching the Swiss nailers making their nails. He keeps a little
journal, in which he describes the process of nailmaking, and
incidentally throws a luminous beam upon himself.

'August 2, 1841.--Clout nailmaking goes on here rather considerably,
and is a very neat and pretty operation to observe. I love a
smith's shop and anything relating to smithery. My father was a

From Interlaken he went to the Falls of the Giessbach, on the
pleasant lake of Brientz. And here we have him watching the shoot
of the cataract down its series of precipices. It is shattered into
foam at the base of each, and tossed by its own recoil as water-dust
through the air. The sun is at his back, shining on the drifting
spray, and he thus describes and muses on what he sees:--

'August 12, 1841.--To-day every fall was foaming from the abundance
of water, and the current of wind brought down by it was in some
places too strong to stand against. The sun shone brightly, and the
rainbows seen from various points were very beautiful. One at the
bottom of a fine but furious fall was very pleasant,--there it
remained motionless, whilst the gusts and clouds of spray swept
furiously across its place and were dashed against the rock.
It looked like a spirit strong in faith and steadfast in the midst
of the storm of passions sweeping across it, and though it might
fade and revive, still it held on to the rock as in hope and giving
hope. And the very drops, which in the whirlwind of their fury
seemed as if they would carry all away, were made to revive it and

Book of the day: