FARADAY, MICHAEL
(1791?1867), English chemist and physicist, was born at Newington, Surrey, on the 22nd of September 1791. His parents had migrated from Yorkshire to London, where his father worked as a blacksmith. Faraday himself became apprenticed to a bookbinder. The letters written to his friend Benjamin Abbott at this time give a lucid account of his aims in life, and of his methods of self-culture, when his mind was beginning to turn to the experimental study of nature. In 1812 Mr Dance, a customer of his master, took him to hear four lectures by Sir Humphry Davy. Faraday took notes of these lectures, and afterwards wrote them out in a fuller form. Under the encouragement of Mr Dance, he wrote to Sir H. Davy, enclosing these notes. “The reply was immediate, kind and favourable.” He continued to work as a journeyman bookbinder till the 1st of March 1813, when he was appointed assistant in the laboratory of the Royal Institution of Great Britain on the recommendation of Davy, whom he accompanied on a tour through France, Italy and Switzerland from October 1813 to April 1815. He was appointed director of the laboratory in 1825; and in 1833 he was appointed Fullerian professor of chemistry in the institution for life, without the obligation to deliver lectures. He thus remained in the institution for fifty-four years. He died at Hampton Court on the 25th of August 1867.
Faraday’s earliest chemical work was in the paths opened by Davy, to whom he acted as assistant. He made a special study of chlorine, and discovered two new chlorides of carbon. He also made the first rough experiments on the diffusion of gases, a phenomenon first pointed out by John Dalton, the physical importance of which was more fully brought to light by Thomas Graham and Joseph Loschmidt. He succeeded in liquefying several gases; he investigated the alloys of steel, and produced several new kinds of glass intended for optical purposes. A specimen of one of these heavy glasses afterwards became historically important as the substance in which Faraday detected the rotation of the plane of polarization of light when the glass was placed in the magnetic field, and also as the substance which was first repelled by the poles of the magnet. He also endeavoured with some success to make the general methods of chemistry, as distinguished from its results, the subject of special study and of popular exposition. See his work on
Chemical Manipulation
.
But Faraday’s chemical work, however important in itself, was soon completely overshadowed by his electrical discoveries. The first experiment which he has recorded was the construction of a voltaic pile with seven halfpence, seven disks of sheet zinc, and six pieces of paper moistened with salt water. With this pile he decomposed sulphate of magnesia (first letter to Abbott, July 12, 1812). Henceforward, whatever other subjects might from time to time claim his attention, it was from among electrical phenomena that he selected those problems to which he applied the full force of his mind, and which he kept persistently in view, even when year after year his attempts to solve them had been baffled.
His first notable discovery was the production of the continuous rotation of magnets and of wires conducting the electric current round each other. The consequences deducible from the great discovery of H. C. Oersted (21st July 1820) were still in 1821 apprehended in a somewhat confused manner even by the foremost men of science. Dr W. H. Wollaston indeed had formed the expectation that he could make the conducting wire rotate on its own axis, and in April 1821 he came with Sir H. Davy to the laboratory of the Royal Institution to make an experiment. Faraday was not there at the time, but coming in afterwards he heard the conversation on the expected rotation of the wire.
In July, August and September of that year Faraday, at the request of R. Phillips, the editor of the
Annals of Philosophy
, wrote for that journal an historical sketch of electro-magnetism, and he repeated almost all the experiments he described. This led him in the beginning of September to discover the method of producing the continuous rotation of the wire round the magnet, and of the magnet round the wire. He did not succeed in making the wire or the magnet revolve on its own axis. This first success of Faraday in electro-magnetic research became the occasion of the most painful, though unfounded, imputations against his honour. Into these we shall not enter, referring the reader to the
Life of Faraday
, by Dr Bence Jones.
We may remark, however, that although the fact of the tangential force between an electric current and a magnetic pole was clearly stated by Oersted, and clearly apprehended by A. M. Ampere, Wollaston and others, the realization of the continuous rotation of the wire and the magnet round each other was a scientific puzzle requiring no mean ingenuity for its original solution. For on the one hand the electric current always forms a closed circuit, and on the other the two poles of the magnet have equal but opposite properties, and are inseparably connected, so that whatever tendency there is for one pole to circulate round the current in one direction is opposed by the equal tendency of the other pole to go round the other way, and thus the one pole can neither drag the other round and round the wire nor yet leave it behind. The thing cannot be done unless we adopt in some form Faraday’s ingenious solution, by causing the current, in some part of its course, to divide into two channels, one on each side of the magnet, in such a way that during the revolution of the magnet the current is transferred from the channel in front of the magnet to the channel behind it, so that the middle of the magnet can pass across the current without stopping it, just as Cyrus caused his army to pass dryshod over the Gyndes by diverting the river into a channel cut for it in his rear.
We must now go on to the crowning discovery of the induction of electric currents.
In December 1824 he had attempted to obtain an electric current by means of a magnet, and on three occasions he had made elaborate but unsuccessful attempts to produce a current in one wire by means of a current in another wire or by a magnet. He still persevered, and on the 29th of August 1831 he obtained the first evidence that an electric current can induce another in a different circuit. On the 23rd of September he writes to his friend R. Phillips: “I am busy just now again on electro-magnetism, and think I have got hold of a good thing, but can’t say. It may be a weed instead of a fish that, after all my labour, I may at last pull up.” This was his first successful experiment. In nine more days of experimenting he had arrived at the results described in his first series of “Experimental Researches” read to the Royal Society on the 24th of November 1841. By the intense application of his mind he had thus brought the new idea, in less than three months from its first development, to a state of perfect maturity.
During his first period of discovery, besides the induction of electric currents, Faraday established the identity of the electrification produced in different ways; the law of the definite electrolytic action of the current; and the fact, upon which he
laid great stress, that every unit of positive electrification is
related in a definite manner to a unit of negative electrification,
so that it is impossible to produce what Faraday called “an
absolute charge of electricity” of one kind not related to an
equal charge of the opposite kind. He also discovered the
difference of the capacities of different substances for taking
part in electric induction. Henry Cavendish had before 1773
discovered that glass, wax, rosin and shellac have higher specific
inductive capacities than air, and had actually determined the
numerical ratios of these capacities, but this was unknown both
to Faraday and to all other electricians of his time, since Cavendish’s
Electrical Researches
remained unpublished till 1879.
The first period of Faraday’s electrical discoveries lasted ten
years. In 1841 he found that he required rest, and it was not till
1845 that he entered on his second great period of research, in
which he discovered the effect of magnetism on polarized light,
and the phenomena of diamagnetism.
Faraday had for a long time kept in view the possibility of
using a ray of polarized light as a means of investigating the
condition of transparent bodies when acted on by electric and
magnetic forces. Dr Bence Jones (
Life of Faraday
, vol. i. p. 362)
gives the following note from his laboratory book on the 10th of
September 1822:?
“Polarized a ray of lamplight by reflection, and endeavoured to
ascertain whether any depolarizing action (was) exerted on it by
water placed between the poles of a voltaic battery in a glass cistern;
one Wollaston’s trough used; the fluids decomposed were pure
water, weak solution of sulphate of soda, and strong sulphuric acid;
none of them had any effect on the polarized light, either when
out of or in the voltaic circuit, so that no particular arrangement
of particles could be ascertained in this way.”
Eleven years afterwards we find another entry in his notebook
on the 2nd of May 1833 (
Life
, by Dr Bence Jones, vol. ii. p. 29).
He then tried not only the effect of a steady current, but the
effect on making and breaking contact.
“I do not think, therefore, that decomposing solutions or substances
will be found to have (as a consequence of decomposition or
arrangement for the time) any effect on the polarized ray. Should
now try non-decomposing bodies, as solid nitre, nitrate of silver,
borax, glass, &c., whilst solid, to see if any internal state induced,
which by decomposition is destroyed,
i.e.
whether, when they cannot
decompose, any state of electrical tension is present. My borate
of glass good, and common electricity better than voltaic.”
On the 6th of May he makes further experiments, and concludes:
“Hence I see no reason to expect that any kind of
structure or tension can be rendered evident, either in decomposing
or non-decomposing bodies, in insulating or conducting
states.”
At last, in 1845, Faraday attacked the old problem, but this
time with complete success. Before we describe this result we
may mention that in 1862 he made the relation between magnetism
and light the subject of his very last experimental work.
He endeavoured, but in vain, to detect any change in the lines
of the spectrum of a flame when the flame was acted on by a
powerful magnet.
This long series of researches is an instance of his persistence.
His energy is shown in the way in which he followed up his
discovery in the single instance in which he was successful.
The first evidence which he obtained of the rotation of the plane
of polarization of light under the action of magnetism was on
the 13th of September 1845, the transparent substance being
his own heavy glass. He began to work on the 30th of August
1845 on polarized light passing through electrolytes. After
three days he worked with common electricity, trying glass,
heavy optical glass, quartz, Iceland spar, all without effect, as on
former trials. On the 13th of September he worked with lines
of magnetic force. Air, flint, glass, rock-crystal, calcareous spar
were examined, but without effect.
“Heavy glass was experimented with. It gave no effects when
the
same magnetic poles
or the
contrary
poles were on opposite sides
(as respects the course of the polarized ray), nor when the same
poles were on the same side either with the constant or intermitting
current. But when contrary magnetic poles were on the same side
there was an effect produced on the polarized ray, and thus magnetic
force and light were proved to have relations to each other. This
fact will most likely prove exceedingly fertile, and of great value in
the investigation of the conditions of natural force.”
He immediately goes on to examine other substances, but with
“no effect,” and he ends by saying, “Have got enough for
to-day.” On the 18th of September he “does an excellent day’s
work.” During September he had four days of work, and in
October six, and on the 6th of November he sent in to the Royal
Society the nineteenth series of his “Experimental Researches,”
in which the whole conditions of the phenomena are fully specified.
The negative rotation in ferro-magnetic media is the only
fact of importance which remained to be discovered afterwards
(by M. E. Verdet in 1856).
But his work for the year was not yet over. On the 3rd of
November a new horseshoe magnet came home, and Faraday
immediately began to experiment on the action in the polarized
ray through gases, but with no effect. The following day he
repeated an experiment which had given no result on the 6th of
October. A bar of heavy glass was suspended by silk between
the poles of the new magnet. “When it was arranged, and had
come to rest, I found I
could
affect it by the magnetic forces
and give it position.” By the 6th of December he had sent
in to the Royal Society the twentieth, and on the 24th of
December the twenty-first, series of his “Researches,” in which
the properties of diamagnetic bodies are fully described. Thus
these two great discoveries were elaborated, like his earlier one,
in about three months.
The discovery of the magnetic rotation of the plane of polarized
light, though it did not lead to such important practical applications
as some of Faraday’s earlier discoveries, has been of the
highest value to science, as furnishing complete dynamical
evidence that wherever magnetic force exists there is matter,
small portions of which are rotating about axes parallel to the
direction of that force.
We have given a few examples of the concentration of his
efforts in seeking to identify the apparently different forces of
nature, of his far-sightedness in selecting subjects for investigation,
of his persistence in the pursuit of what he set before him,
of his energy in working out the results of his discoveries, and
of the accuracy and completeness with which he made his final
statement of the laws of the phenomenon.
These characteristics of his scientific spirit lie on the surface
of his work, and are manifest to all who read his writings. But
there was another side of his character, to the cultivation of
which he paid at least as much attention, and which was reserved
for his friends, his family and his church. His letters and his
conversation were always full of whatever could awaken a
healthy interest, and free from anything that might rouse ill-feeling.
When, on rare occasions, he was forced out of the region
of science into that of controversy, he stated the facts and let
them make their own way. He was entirely free from pride
and undue self-assertion. During the growth of his powers he
always thankfully accepted a correction, and made use of every
expedient, however humble, which would make his work more
effective in every detail. When at length he found his memory
failing and his mental powers declining, he gave up, without
ostentation or complaint, whatever parts of his work he could
no longer carry on according to his own standard of efficiency.
When he was no longer able to apply his mind to science, he
remained content and happy in the exercise of those kindly
feelings and warm affections which he had cultivated no less
carefully than his scientific powers.
The parents of Faraday belonged to the very small and isolated
Christian sect which is commonly called after Robert Sandeman.
Faraday himself attended the meetings from childhood; at the
age of thirty he made public profession of his faith, and during
two different periods he discharged the office of elder. His
opinion with respect to the relation between his science and his
religion is expressed in a lecture on mental education delivered
in 1854, and printed at the end of his
Researches in Chemistry
and Physics
.
“Before entering upon the subject, I must make one distinction
which, however it may appear to others, is to me of the utmost
importance. High as man is placed above the creatures around
him, there is a higher and far more exalted position within his
view; and the ways are infinite in which he occupies his thoughts
about the fears, or hopes, or expectations of a future life. I believe
that the truth of that future cannot be brought to his knowledge
by any exertion of his mental powers, however exalted they may
be; that it is made known to him by other teaching than his own,
and is received through simple belief of the testimony given. Let
no one suppose for an instant that the self-education I am about to
commend, in respect of the things of this life, extends to any considerations
of the hope set before us, as if man by reasoning could
find out God. It would be improper here to enter upon this subject
further than to claim an absolute distinction between religious
and ordinary belief. I shall be reproached with the weakness of
refusing to apply those mental operations which I think good in
respect of high things to the very highest. I am content to bear
the reproach. Yet even in earthly matters I believe that ‘the invisible
things of Him from the creation of the world are clearly
seen, being understood by the things that are made, even His
eternal power and Godhead’; and I have never seen anything
incompatible between those things of man which can be known by
the spirit of man which is within him and those higher things concerning
his future, which he cannot know by that spirit.”
Faraday gives the following note as to this lecture:?
“These observations were delivered as a lecture before His Royal
Highness the Prince Consort and the members of the Royal Institution
on the 6th of May 1854. They are so immediately connected
in their nature and origin with my own experimental life, considered
either as cause or consequence, that I have thought the close of
this volume not an unfit place for their reproduction.”
As Dr Bence Jones concludes?
“His standard of duty was supernatural. It was not founded on
any intuitive ideas of right and wrong, nor was it fashioned upon
any outward experiences of time and place, but it was formed
entirely on what he held to be the revelation of the will of God in
the written word, and throughout all his life his faith led him to
act up to the very letter of it.”
Published Works.?Chemical Manipulation, being Instructions to
Students in Chemistry
(1 vol., John Murray, 1st ed. 1827, 2nd 1830,
3rd 1842);
Experimental Researches in Electricity
, vols. i. and ii.,
Richard and John Edward Taylor, vols. i. and ii. (1844 and 1847);
vol. iii. (1844); vol. iii. Richard Taylor and William Francis (1855);
Experimental Researches in Chemistry and Physics
, Taylor and
Francis (1859);
Lectures on the Chemical History of a Candle
(edited
by W. Crookes) (Griffin, Bohn & Co., 1861);
On the Various Forces
in Nature
(edited by W. Crookes) (Chatto & Windus, no date).
Biographies.
?
Faraday as a Discoverer
, by John Tyndall (Longmans,
1st ed. 1868, 2nd ed. 1870);
The Life and Letters of Faraday
,
by Dr Bence Jones, secretary of the Royal Institution, in 2 vols.
(Longmans, 1870);
Michael Faraday
, by J. H. Gladstone, Ph.D.,
F.R.S. (Macmillan, 1872);
Michael Faraday; his Life and Work
,
by S. P. Thompson (1898).
(
J. C. M.
)