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F A K A D A Y 







The right of translation it reserved. 




SOME YEAKS AGO I accompanied Mr. FAEADAY to 
a little Photographic Studio in Lambeth, with the 
view of exchanging portraits. The Frontispiece is 
engraved from one of the negatives taken on that 
occasion, and which is now in the possession of 
Dr. Bence Jones. 

The portrait facing p. 79 is from a Daguerreotype 
by Claudet, the property of Mrs. Faraday, taken 
when her husband was about fifty years old. Its 
position in the book has been chosen with reference 
to his age. 


2lst Feb. 1868. 





TIONS TO PHYSICS . . V ; ' . .12 


POINTS OF CHARACTER ';',. . . . .30 

CHEMISTRY . . . . . . .41 












SUMMARY ....... 145 




IT has been thought desirable to give you and the 
world some image of MICHAEL FARADAY, as a scien- 
tific 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 dis- 
coveries 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 impos- 
sible 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 imme- 
diately 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 fell finally asleep at 
Hampton Court, on August 25, 1867. Believing, as 
I do a in the general truth of the doctrine of here- 
ditary 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 un- 


usual 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.* Mr. 

* Here is Davy's recommendation of Faraday, presented to the 
managers of the Koyal 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 Insti- 
tution 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 situa- 
tion. His habits seem good ; his disposition active and cheerful, and 


Gassiot has lately favoured me with, the following 
reminiscence of this time : 

' Clapham Common, Surrey, 

' November 28, 1867. 

6 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 Eayal 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. 

6 Davy held the joint office of Professor of Chemis- 
try and Director of the Laboratory; he ultimately 
gave up the former to the late Professor Brande, but 
he insisted that Earaday should be appointed Direc- 
tor of the Laboratory, and, as Faraday told me, this 

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.' 


enabled him on subsequent occasions to hold a defi- 
nite position in the Institution, in which he was 
always supported by Davy. I believe he held tha* 
office to the last. 

6 Believe me, my dear Tyndall, yours truly, 

' J. P. GrASSIOT. 
'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. 

c 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 philoso- 
pher,* which happened thus : Whilst an apprentice, 
I, for amusement, learnt a little chemistry and other 
parts of philosophy, and felt an eager desire to pro- 
ceed 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 

* Paraday loved this word and employed it to the last ; he had an 
intense dislike to the modern term physicist. 


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 man- 
ner 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,* 
on the occasion of the death of Mrs. Marcet. The 
letter is dated Sept. 2, 1858 : 

c 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 13, in the year 1804, 
remained there eight years, and during the chief 
part of the time bound books. Now it was in those 
books, in the hours after work, that I found the be- 
ginning of my philosophy. There were two that 
especially helped me, the "Encyclopaedia Britannica," 

* To whom I am indebted for a copy of the original letter. 


from which. I gained my first notions of electricity, 
and Mrs. Marcet's " Conversations 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 " Encyclo- 
psedia." 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 know- 
ledge 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 per- 
sonally 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 in Baker-street. He took my arm at 
the door, and, pressing it to his side in his warm 
genial way, said, c 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 to- 
wards 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 bny some cards as an excuse for our being 
there. He asked the woman her name her prede- 


cessor's name his predecessor's name. f 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. 5 ( 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 Eoyal Institution published ' The Quarterly 
Journal of Science,' the precursor of our own ' Pro- 
ceedings.' 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 experi- 
mented upon ' Sounding Flames.' Professor Auguste 
De la Rive, father of our present excellent De la 
Rive, had investigated those sounding flames, and 


had applied to them an explanation which com- 
pletely accounted for a class of sounds discovered by 
De la Eive himself. By a few simple and conclusive 
experiments, Faraday proved that the explanation 
was 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 ; work- 
ing hard for his master and storing and strengthen- 
ing 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 Eoyal 
Institution. There for forty-six years they lived to- 
gether, 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. 


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 Institu- 
tion. 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. 



OEESTED, in 1820, discovered the action of a voltaic 
current on a magnetic needle ; and immediately 
afterwards the splendid intellect of Ampere suc- 
ceeded 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 Eoyal Institution. 
This was well calculated to attract Faraday's atten- 
tion to the subject. He read much about it ; and in 
the months of July, August, and September, he wrote 
e a history of the progress of electro-magnetism/ 
which he published in Thomson's ( Annals of Phi- 
losophy.' Soon afterwards he took up the subject of 
( Magnetic Eotations,' and on the morning of Christ- 
mas-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 accus- 
tomed 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 


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 : 

6 DEAR SIR, The oil you noticed yesterday turns 
out to be liquid chlorine. 

c Tours faithfully, 

< M. FARADAY.' * 

The gas had been liquefied by its own pressure. Fa- 
raday 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 : c 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 it would become fluid as a hydrate ; 
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 atmospheres to the liquefaction of 
muriatic gas. Faraday continued the experiments, 

* Paris : Life of Davy, p. 391. 


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 investiga- 
tions 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 ag- 
gregation. The account of the first investigation 
was read before the Eoyal Society on April 10, 1823, 
and was published, in Faraday's name, in the ' Phi- 
losophical Transactions.' The second memoir was 
sent to the Eoyal Society on December 19, 1844. I 
may add that while he was conducting his first ex- 
periments 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 exceed- 
ingly 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. 
Eankine, 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 com- 
mittee, to which Sir John Herschel and Mr. Dollond 
also belonged, appointed by the Eoyal Society to 
examine, and if possible improve, the manufacture 
of glass for optical purposes. Their experiments 
continued till 1829, when the account of them con- 
stituted 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 Eoyal 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, f On the 
Manufacture of Glass for Optical Purposes,' was de- 
livered at the close of 1829. It is a most elaborate 


and conscientious description of processes, pre- 
cautions, and results : the details were so exact and 
so minute, and the paper consequently so long, thai 
three successive sittings of the Eoyal Society were 
taken up by the delivery of the lecture.* 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. f 

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 Eoyal Institution ; and 
it was at this time, and with a view of assisting him 
at the furnace, that Faraday engaged Sergeant An- 
derson, of the Royal Artillery, the respectable, truth- 
ful, and altogether trustworthy man whose appearance 

* Vis. November 19, December 3 and 10. 

t 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 re- 
collect, that I mentioned it to Sir James (then Mr.) South ; and, in con- 
sequence, 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," Encyclopedia Metropolitans). 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.' 



here is so fresh in our memories. Anderson con- 
tinued to be the reverential helper of Faraday and 
the faithful servant of this Institution for nearly 
forty years.* 

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 011 
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 

* 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.IY (Erp. Researches, vol. iii. p. 3, footnote.) 


this direction. I have heard him say that this paper 
on vibrating surfaces was too heavily laden with 


The work thus far 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, lec- 
turing, 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 une- 

* He used to say that it required twenty years of work to make a 
man in Physical Science ; the previous period being one of infancy. 

c 2 


lectrified 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, lumi- 
nous in different degrees to different minds, and 
he hardly trusted himself to reason upon an ex- 
periment 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 pro- 
duced 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 pre-occupation. 


He began his experiments 'on the induction of 
electric currents ' by composing a helix of two insu- 
lated 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 con- 
nection with the battery was made, and while the 
current flowed, no effect whatever was observed at 
the galvanometer. But he never accepted an experi- 
mental 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 pro- 
ducing, during its flow, any sensible result upon the 

6 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 mo- 
ment when he made contact with the battery ; that 
the needle would afterwards return to its former posi- 
tion 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 com- 
pletion 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 in- 
stant only, and partook more of the nature of the 
electric wave from a common Ley den 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 coin- 
cided 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 
Eeymond to express a certain electric condition of 
the nerves, and Professor Clerk Maxwell has ably 
denned 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 cur- 
rent flowed was then shown by Faraday to be suf- 
ficient to arouse in the neutral wire an induced 
current, opposed in direction to the inducing cur- 
rent; 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 in- 
duced current was generated. 

Faraday has been called a purely inductive philo- 
sopher. A great deal of nonsense is, I fear, uttered 
in this land of England about induction and deduc- 
tion. 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 ex- 
periments were executed merely to test his deductions 


from that theory. Starting from the discovery of 
Oersted, the celebrated 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 re- 
ciprocal actions, now attempted to effect the evolu- 
tion of electricity from magnetism. Eound 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 magnetized, 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 imme- 
diately. On interrupting the circuit, a whirl of the 
needle in the opposite direction occurred. It was 
only during the time of magnetization or demagne- 
tization that these effects were produced. The in- 
duced currents declared a change of condition only, 
and they vanished the moment the act of magnetiza- 
tion or demagnetization was complete. 

The effects obtained with the welded ring were 
also obtained with straight bars of iron. Whether 
the bars were magnetized by the electric current, or 


were excited by the contact of permanent steel mag- 
netSj 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 perma- 
nent steel magnet into a coil of wire. A rush of 
electricity through the coil accompanied the inser- 
tion 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 fact's, 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 power- 
ful permanent magnet of the Royal Society, and ob- 
tained with it, in an exalted degree, all the foregoing- 

And now he turned the light of these discoveries 
upon the darkest physical phenomenon of that day. 
Aragp 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 by both 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 re- 
mained a mystery. Faraday always recommended the 
suspension of judgment in cases of doubt. ' I have 
always admired,' he says, ' the prudence and philo- 
sophical reserve shown by M. Arago in resisting the 
temptation to give a theory of the effect he had dis- 
covered, 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 cur- 
rents 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 direc- 


tion 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 Eoyal 
Society, and connecting the axis and the edge of the 
disk, each by a wire with a galvanometer, he ob- 
tained, 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 cur- 
rent 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 them- 
selves in certain determinate lines called magnetic 
curves. In 1831, Faraday for the first time called 
these curves 6 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 Eoyal Society on the 24th of November, 


On January 12, 1832, be communicated to the 
Boyal 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 70. 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 galvano- 
meter. '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, deflect- 
ing 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 ob- 
tained 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 con- 
ducting 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 galvano- 
meter from the rotating magnet. He remarks upon 
the ' singular independence ' of the magnetism and the 
body of the magnet which carries it. The steel be- 
haves 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 twirl- 
ing 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 rela- 
tive 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 under- 
neath 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 neutralize 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 con- 
ducting 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 worst. Still, though ex- 
periment 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 elec- 


trie 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 des- 
cribed, 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.* 

* 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 ex- 
periments, 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 Prof essorDani ell, who was standing near Faraday, 
inquired what was going on. The Professor explained to him as popu- 
larly 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 


Three years subsequent to the publication of these 
researches, that is to say on January 29, 1835, 
Faraday read before the Eoyal Society a paper ' On 
the influence by induction of an electric current 
upon itself.' A shock and spark of a peculiar cha- 
racter had been observed by a young man named 
William Jen kin, 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 investi- 
gation 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 dis- 
covery 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 

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." ' 



arising from its illustration; and guided by the prin- 
ciple lie 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-elec- 
tric 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 al- 
lowed 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 dis- 
covering 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 ex- 
pressed 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 

D 2 


state, but having grown up to maturity, witness its 
powers, and see what endeavours to make it useful 
have done. 5 


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 communi- 
cated 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/ accom- 
panied 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 impu- 
tations on his character. The style of this letter is 
unexceptionable, for Faraday could not write other- 
wise 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 incom- 
plete. 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 
c 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 e 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, 

np to 1832. 


' Papers of mine, published in octavo, in the " Quar- 
terly 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 philo- 
sophy and manner it could have been much better 
done. I still hope the collection may be of great use 
to me. 


'Aug. 18, 1832.' 

c JSTone 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. c 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, 6th Oct., 1855. 

C MT DEAK 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 misinterpret- 
ed 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 op- 
posing parties, if WTong, 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 suc- 
ceeded I hcpe, 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.* 

' Yours, very truly, 



I have already once used the word e 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 c doubtful knowledge,' and ever 
tended either to transfer it into the region of un- 
doubtful knowledge, or of certain and definite igno- 
rance. 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. 

* 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 


6 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. 5 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 manifesta- 
tions 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 c Identity of Electricities.' His paper upon 
this subject was read before the Royal Society on 
January the 10th and 17th, 1833. 

After he had proved to his own satisfaction the 
identity of electricities, he tried to compare them 
quantitatively together. The terms quantity and in- 
tensity, which Faraday constantly used, need a word 
of explanation here. He might charge a single Ley- 
den 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 ma- 
chine electricity, whether it was condensed in a small 
battery or diffused over a large one. Thus the elec- 
tricity developed by thirty turns of his machine pro- 
duced, under very variable conditions of battery sur- 
face, the same deflections. Hence he inferred the 
possibility of comparing as regards quantity, elec- 
tricities which differ greatly from each other in 

His object now is to compare frictional with vol- 
taic 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 is liberated. Then he immersed two 
wires, one of zinc, the other of platinum, each T Vth 
of an inch in diameter, to a depth of -fths of an 
inch in acidulated water during eight beats of his 
watch, or 3 ths 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 dis- 
tinctly 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 de- 
composition 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 de- 
composition of a single .grain of water. He is al- 
most 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 quan- 
tity to a powerful thunderstorm. Thus his mind 
rises from the minute to the vast, expanding involun- 
tarily from the smallest laboratory fact till it em- 
braces the largest and grandest natural phenomena.* 

* Buff finds the quantity of electricity associated with one milli- 
gramme 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 1,000 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 Maas- 
i, 1856, p. 262.) 


In reality, however, lie 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 transmission. 

On May 23, 1833, he read a paper before the 
Royal Society e On a new Law of Electric Conduc- 
tion.' 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 mole- 
cule 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 decompo- 
sition. 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 in- 
finitesimal quantity of electricity might pass through 
a compound liquid without producing its decomposi- 
tion. 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 man- 
ner that no trace of electricity can pass through a 
liquid compound without producing its equivalent 

Faraday has now got fairly entangled amid the 
chemical phenomena of the pile, and here his pre- 
vious 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 Eoyal Society ' On 
Electro-chemical Decomposition,' in which he seeks 
to answer these questions. The notion had been 

* Faraday, sa Vie et ses Travaux, p. 20. 


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 ap- 
pears 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 sepa- 
rate 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 conduc- 
tor of an electric machine, and the other to the gas- 
pipes of this building. These he called his 'discharg- 
ing 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 sul- 
phuric 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 decom- 
position 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 dis- 
charging 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 con- 
nected 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, e the poles are entirely abandoned, 
but we have still electro-chemical 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 after- 
wards reiterates this view: the evolved substances are 
expelled from the decomposing body, and ' not drawn 
out by an attraction. 9 

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 Lec- 
ture, given in 1806, which he says ' is almost entirely 
occupied in the consideration of electro-chemical 
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 electro-chemical 
action might be drawn up, differing essentially from 
each other, yet all agreeing with the statement there 

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 perma- 
nent value ; but little h elp 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 re-compositions, 
enunciated and developed by Grothuss and Davy, 
he does not, I think, help us to any definite con- 
ception 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 i 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 Eive ; 
but the fact is, that both he and De la Eive 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 phi- 
losophy of the voltaic pile. 

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 electro- 
chemical decomposition interrupted by an inquiry 
into ' the power of metals and other solids, to induce 

E 2 


the combination of gaseous bodies.' This in- 
quiry, which, was received by the Royal Society on 
ISfov. 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 construc- 
tion 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 libe- 
rated 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 six- 
teen 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 re- 
verse 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 succes- 
sion ; but when the current is reversed, the hydro- 
gen is liberated upon the cleansed wire, and then its 
bubbles also become small. 


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 home.* 

No man ever felt this tyranny of symbols more 
deeply than Earaday, and no man was ever more as- 
siduous 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, re- 
ceived 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.f 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 neutral 
term Electrodes. He applied the term Electrolyte to 

* 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 Eoyal Institution, vol. ii. p. 132. 

f In 1838 he expresses himself thus: 'The word current is so ex- 
pressive 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. Eesear., vol. i. 
p. 515. (1617.) 


every substance which can be decomposed by the cur- 
rent, and the act of decomposition he called Electro- 
lysis. 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. 
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 elec- 
tricity 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 Measurer of Voltaic electricity. 

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. Becquei-el, 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 sub- 
jected these secondary actions to an exhaustive ex- 
amination. Instructed by his experiments, and ren- 
dered competent by them to distinguish between 
primary and secondary results, he proceeds to es- 
tablish the doctrine of c Definite Electro-chemical 

Into the same circuit he introduced his voltameter, 
which consisted of a graduated tube filled with acidu- 
lated water and provided with platinum plates for 
the decomposition of the water, and also a cell con- 
taining chloride of tin. Experiments already referred 
to had taught him that this substance, though an in- 
sulator 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 equi- 
valent, 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 repre- 
sented 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 equi- 
valent of tin. Thus both the water and the chloride 
were broken up in proportions expressed by their re- 
spective 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 con- 
stituents of the molecules of the chloride of tin. The 
fact is typical. With the indications of his volta- 
meter he compared the decomposition of other sub- 
stances both singly and in series. He submitted his 
conclusions to numberless tests. He purposely intro- 


duced 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. 


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, ' Yolta.' 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 passion- 
less laws and phenomena of external nature, one might 
suppose that their investigation and discussion would 
be completely withdrawn from the region of the feel- 
ings, and pursued by the cold dry light of the intel- 
lect 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 thm 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 anci Undulation was of this 
fierce character; and scarcely less fierce for many 
years was the contest as to the origin and mainten- 
ance of the power of the voltaic pile. Yolta 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 conduc- 
tor ; for when any two metals were connected by a 
third, their relation to each other was such that a 
complete neutralization of the electric motion was 
the result. Yolta'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. 

Yolta himself knew nothing of the chemical phe- 
nomena 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 illus- 
tration 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,' re- 
ceived by the Royal Society on the 7th April, 1834. 
His position in the controversy might have been pre- 
dicted. 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 were 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 compe- 
tent therefore to allow the electricity of contact to 
flow through them if it were able to form a cur- 
rent, were absolutely powerless when chemically in- 

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 in- 
terval before contact. Faraday's friend, Mr. Gassiot, 
solved this problem. He erected a battery of 4,000 
cells, and with it urged a stream of sparks from ter- 
minal 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 con- 
tact theory. These indeed were men of too great 
intellectual weight and insight lightly to take up, or 
lightly to abandon a theory. Faraday therefore re- 


snmed 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 diffi- 
culty about the neck of the contact theory, until in 
its eiforts 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 per- 
sistently 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 that of natural 

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, i assumes that a force which is able to over- 
come 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 mat- 
ter, 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/orra 
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 conver- 
tibility 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. 9 

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 dis- 
tinct enunciation by individuals, it dwells more or 
less clearly in the general scientific mind. The in- 
tellectual plateau is already high, and our disco- 
verers are those who, like peaks above the plateau, 
rise a little above the general level of thought at the 

But many years prior even to the foregoing ut- 
terance of Faraday, a similar argument had been 


employed. I quote here with equal pleasure and 
admiration the following passage written by Dr. 
Eoget 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 impos- 
sibility of obtaining by their agency a perpetual 
effect j or in other words a perpetual motion. But 
the electro-motive force, ascribed by Yolta 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 indepen- 
dently, 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 



The burst of power which had filled the four pre- 
ceding years with an amount of experimental work 
unparalleled in the history of science partially sub- 
sided in 1835, and the only scientific paper con- 
tributed by Faraday in that year was a comparatively 
unimportant one, ' On an improved Form of the 
Voltaic Battery.' He brooded for a time : his expe- 
riments on electrolysis had long filled his mind ; he 

* 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 experi- 
ments 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 Jfirst 
to give the contact theory this new form, in his celebrated essay, Veber 
die Erhaltung der Kraft, p. 45. 


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 elec- 
trolyte; 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 or- 
dinary electric induction was also transmitted and 
sustained by the action of ( contiguous particles. 9 

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, c 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 media- 
tion of anything else, by and through which this 
action and force may be conveyed from one to an- 
other, is to me so great an absurdity, that I believe 


no man who has in philosophical matters a compe- 
tent faculty of thinking, can ever fall into it. Gravity 
must be caused by an agent acting constantly ac- 
cording to certain laws ; but whether this agent be 
material or immaterial, I have left to the considera- 
tion of my readers.' * 

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 ex- 
periences in conceiving of action at sensible dis- 
tances, besets it also when it attempts to conceive 
of action at insensible distances. Still the investiga- 
tion of the point whether electric and magnetic effects 
were wrought out through the intervention of con- 
tiguous 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 as- 
certain whether electric action ever takes place in 
curved lines. This once proved, it would follow that 
the action is carried on ly means of a medium sur- 

* Newton's third letter to Bentley. 


rounding the electrified bodies. His experiments in 
1837 reduced, in his opinion, this point to demon- 
stration. 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 bend- 
ing 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 electri- 
city. It acted by induction upon the concave surface 
of the latter, and he examined how this act of in- 
duction 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 Ley den 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 sper- 
maceti 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 dis- 
charge of the apparatus, no trace of electricity was 
found upon its knob. But after a time electricity 
was found there, the charge having gradually re- 
turned 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 lie concluded 
that the force of induction is propagated from par- 
ticle 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 Ca- 
pacity. 9 

Faraday visualizes with the utmost clearness the 
state of his contiguous particles ; one after another 
they become charged, each succeeding particle de- 
pending 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 sper- 
maceti and water, to solutions, and then on to chlo- 
rides, 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 mole- 
cular discharge is what we call conduction. Con- 
duction 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 

Though they are often obscure, a fine vein of 
philosophic thought runs through those investiga- 
tions. 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 mole- 
cules of his dielectrics. It would, however, be easy 
to criticise these researches, easy to show the loose- 
ness, and sometimes the inaccuracy, of the phraseo- 
logy employed ; but this critical spirit will get little 
good out of Faraday. Eather let those who ponder 
his works seek to realise the object he set before 
him, not permitting his occasional vagueness to in- 
terfere 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 man- 
ner 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 lie works at the very boundaries of our know- 
ledge, and that his mind habitually dwells in the 
' boundless contiguity of shade ' by which that know- 
ledge 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 elec- 
tricity required time to pass through a wire, the cur- 
rent reaching the middle of the wire later than its 
two ends. ' If,' says Faraday, c the two ends of the 
wire in Professor Wheatstone's experiments were 
immediately connected with two large insulated me- 
tallic surfaces exposed to the air, so that the primary 
act of induction, after making the contact for dis- 
charge, 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 Ley den battery, then 


the retardation of the spark would be much greater.' 
This was only a prediction, for the experiment was 
not made.* 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 In- 
duction 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 im- 
possibility is by no means evident. The key to the 
difficulty is this. He looks upon every insulated con- 
ductor as the inner coating of a Leyden jar. An in- 
sulated sphere in the middle of a room is to his mind 

* If Sir Charles Wheatstone could be induced to take up his mea- 
surements once more, varying the substances through which, and the 
conditions under which the current is propagated, he might render great 
service to science, both theoretic and experimental. 


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 Ley den 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 abolished 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 me- 
moirs 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 im- 
perishable importance. 


The last of these memoirs was dated from the 
Royal Institution in June, 1838. It concludes the 
first volume of his 6 Experimental Eesearches on 
Electricity.' In 1840, as already stated, he made his 
final assault on the Contact Theory, from which it 
never recovered.* He was now feeling the effects of 
the mental strain to which he had been subjected for 

* See note, p. 66. 


so many years. During these years lie 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, 
6 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 consti- 
tuents ; 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 2nd, 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 smith. 9 

From Interlaken he went to the Falls of the Giess- 
bach, 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 12th, 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 give it greater beauty.' 


London Lougmar,.'; & C 



But we must quit the man and go on to the dis- 
coverer: we shall return for a brief space to his 
company by-and-by. Carry your thoughts back to 
his last experiments, and see him endeavouring to 
prove that induction is due to the action of con- 
tiguous particles. He knew that polarized light was 
a most subtle and delicate investigator of molecular 
condition. He used it in 1834 in exploring his elec- 
trolytes, and he tried it in 1838 upon his dielectrics. 
At that time he coated two opposite faces of a glass 
cube with tinfoil, connected one coating with his 
powerful electric machine and the other with the 
earth, and examined by polarized light the condition 
of the glass when thus subjected to strong electric 
influence. He failed to obtain any eifect, still he 
was persuaded an action existed, and required only 
suitable means to call it forth. 

After his return from Switzerland he was beset by 
these thoughts ; they were more inspired than logi- 
cal : but he resorted to magnets and proved his in- 
spiration true. His dislike of c doubtful knowledge ' 
and his eiforts to liberate his mind from the thraldom 
of hypotheses have been already referred to. Still 
this rebel against theory was incessantly theorizing 


himself. His principal researches are all connected 
by an undercurrent of speculation. Theoretic ideas 
were the very sap of his intellect the source from 
which all his strength as an experimenter was de- 
rived. While once sauntering with him through the 
Crystal Palace, at Sydenham, I asked him what 
directed his attention to the magnetization of light. 
It was his theoretic notions. He had certain views 
regarding the unity and convertibility of natural 
forces; certain ideas regarding the vibrations of 
light and their relations to the lines of magnetic 
force; these views and ideas drove him to investi- 
gation. And so it must always be : the great experi- 
mentalist must ever be the habitual theorist, whether 
or not he gives to his theories formal enunciation. 

Faraday, you have been informed, endeavoured to 
improve the manufacture of glass for optical pur- 
poses. But though he produced a heavy glass of 
great refractive power, its value to optics did not. 
repay him for the pains and labour bestowed on it. 
Now, however, we reach a result established by 
means of this same heavy glass, which made ample 
amends for all. 

In November, 1845, he announced his discovery of 
the ' Magnetization of Light, and the Elumination of 
the Lines of Magnetic Force.' This title provoked 
comment at the time, and caused misapprehension. 


He therefore added an explanatory note; but the 
note left his meaning as entangled as before. In. 
fact Faraday had notions regarding the magnetiza- 
tion of light which were peculiar to himself, and 
untranslatable into the scientific language of the 
time. Probably no other philosopher of his day 
would have employed the phrases just quoted as 
appropriate to the discovery announced in 1845. But 
Faraday was more than a philosopher; he was 'a 
prophet, and often wrought by an inspiration to be 
understood by sympathy alone. The prophetic ele- 
ment in his character occasionally coloured, and even 
injured, the utterance of the man of science ; but 
subtracting that element, though you might have 
conferred on him intellectual symmetry, you would 
have destroyed his motive force. 

But let us pass from the label of this casket to the 
jewel it contains. ' I have long,' he says, f held an 
opinion, almost amounting to conviction, in common, 
I believe, with many other lovers of natural know- 
ledge, that the various forms under which the forces 
of matter are made manifest have one common 
origin; in other words, are so directly related and 
mutually dependent, that they are convertible, as it 
were, into one another, and possess equivalents of 
power in their action. . . . This strong persuasion,' 
he adds, c extended to the powers of light.' And 


then lie examines the action of magnets upon light. 
From conversation with him and Anderson, I should 
infer that the labour preceding this discovery was 
very great. The world knows little of the toil of 
the discoverer. It sees the climber jubilant on the 
mountain top, but does not know the labour expended 
in reaching it. Probably hundreds of experiments 
had been made on transparent crystals before he 
thought of testing his heavy glass. Here is his 
own clear and simple description of the result of 
his first experiment with this substance : ( A piece 
of this glass, about two inches square, and 0*5 
of an inch thick, having flat and polished edges, 
was placed as a diamagnetic* between the poles (not 
as yet magnetized by the electric current), so that 
the polarized ray should pass through its length ; 
the glass acted as air, water, or any other trans- 
parent substance would do ; and if the eye-piece 
were previously turned into such a position that the 
polarized ray was extinguished, or rather the image 
produced by it rendered invisible, then the intro- 
duction of the glass made no alteration in this re- 
spect. In this state of circumstances, the force of 

* ' By a diamagnetic,' says Faraday, ' I mean a body through which 
lines of magnetic force are passing, and which does not by their action 
assume the usual magnetic state of iron or loadstone.' Faraday sub- 
sequently used this term in a different sense from that here given, 
as will immediately appear. 


the electro-magnet was developed by sending an 
electric current through its coils, and immediately 
the image of the lamp-flame became visible, and 
continued so as long as the arrangement continued 
magnetic. On stopping the electric current, and so 
causing the magnetic force to cease, the light in- 
stantly disappeared. These phenomena could be 
renewed at pleasure, at any instant of time, and 
upon any occasion, showing a perfect dependence of 
cause and effect.' 

In a beam of ordinary light the particles of the 
luminiferous ether vibrate in all directions perpen- 
dicular to the line of progression ; by the act of polar- 
ization, performed here by Faraday, all oscillations 
but those parallel to a certain plane are eliminated. 
When the plane of vibration of the polarizer co- 
incides with that of the analyzer, a portion of the 
beam passes through both ; but when these two 
planes are at right angles to each other, the beam 
is extinguished. If by any means, while the po- 
larizer and analyzer remain thus crossed, the plane 
of vibration of the polarized beam between them 
could be changed, then the light would be, in part at 
least, transmitted. In Faraday's experiment this was 
accomplished. His magnet turned the plane of po- 
larization of the beam through a certain angle, and 
thus enabled it to get through the analyzer; so 

c 2 


that ' the magnetization of light and the illumina- 
tion of the magnetic lines of force ' becomes, when 
expressed in the language ot modern theory, the ro- 
tation of the plane of polarization. 

To him, as to all true philosophers, the main value 
of a fact was its position and suggestiveness in the 
general sequence of scientific truth. Hence, having 
established the existence of a phenomenon, his habit 
was to look at it from all possible points of view, and 
to develop its relationship to other phenomena. He 
proved that the direction of the rotation depends 
upon the polarity of his magnet; being reversed 
when the magnetic poles are reversed. He showed 
that when a polarized ray passed through his heavy 
glass in a direction parallel to the magnetic lines of 
force, the rotation is a maximum, and that when the 
direction of the ray is at right angles to the lines of 
force, there is no rotation at all. He also proved that 
the amount of the rotation is proportional to the length 
of the diamagnetic through which the ray passes. 
He operated with liquids and solutions. Of aqueous 
solutions he tried 150 and more, and found the power 
in all of them. He then examined gases ; but here 
all his efforts to produce any sensible action upon the 
polarized beam were ineffectual. He then passed 
from magnets to currents, enclosing bars of heavy 
glass, and tubes containing liquids and aqueous solu- 


tions within an electro-magnetic helix. A current 
sent through the helix caused the plane of polari- 
zation to rotate, and always in the direction of the 
current. The rotation was reversed when the current 
was reversed. In the case of magnets, he observed 
a gradual, though quick, ascent of the transmitted 
beam from a state of darkness to its maximum bril- 
liancy, when the magnet was excited. In the case of 
currents, the beam attained at once its maximum. 
This he showed to be due to the time required by the 
iron of the electro-magnet to assume its full magnetic 
power, which time vanishes when a current, without 
iron, is employed. f In this experiment,' he says, ' we 
may, I think, justly say that a ray of light is elec- 
trified, and the electric forces illuminated.' In the 
helix, as with the magnets, he submitted air to mag- 
netic influence carefully and anxiously,' but could 
not discover any trace of action on the polarized ray. 
Many substances possess the power of turning 
the plane of polarization without the intervention 
of magnetism. Oil of turpentine and quartz are 
examples ; but Faraday showed that, while in one di- 
rection, that is, across the lines of magnetic force, his 
rotation is zero, augmenting gradually from this until 
it attains its maximum, when the direction of the ray 
is parallel to the lines of force ; in the oil of turpen- 
tine the rotation is independent of the direction of 


the ray. But lie showed that a still more profound 
distinction exists between the magnetic rotation and 
the natural one. I will try to explain how. Suppose 
a tube with glass ends containing oil of turpentine to 
be placed north and south. Fixing the eye at the 
south end of the tube, let a polarized beam be sent 
through it from the north. To the observer in this 
position the rotation of the plane of polarization, by 
the turpentine, is right-handed. Let the eye be placed 
at the north end of the tube, and a beam be sent 
through it from the south ; the rotation is still right- 
handed. Not so, however, when a bar of heavy glass is 
subjected to the action of an electric current. In this 
case if, in the first position of the eye, the rotation be 
right-handed, in the second position it is left-handed. 
These considerations make it manifest that if a polar- 
ized beam, after having passed through the oil of 
turpentine in its natural state, could, by any means, 
be reflected back through the liquid, the rotation 
impressed upon the direct beam would be exactly 
neutralized by that impressed upon the reflected one. 
.Not so with the induced magnetic effect. Here it is 
manifest that the rotation would be doubled by the 
act of reflection. Hence Faraday concludes that 
the particles of the oil of turpentine which rotate by 
virtue of their natural force, and those which rotate 
in virtue of the induced force, cannot be in the same 


condition. The same remark applies to all bodies 
which possess a natural power of rotating the plane 
of polarization. 

And then he proceeded with exquisite skill and in- 
sight to take advantage of this conclusion. He sil- 
vered the ends of his piece of heavy glass, leaving, 
however, a narrow portion parallel to two edges dia- 
gonally opposed to each other unsilvered. He then 
sent his beam through this uncovered portion, and 
by suitably inclining his glass caused the beam 
within it to reach his eye, first direct, and then after 
two, four, and six reflections. These corresponded to 
the passage of the ray once, three times, five times, 
and seven times through the glass. He thus estab- 
lished with numerical accuracy the exact proportion- 
ality of the rotation, to the distance traversed by the 
polarized beam. Thus in one series of experiments 
where the rotation required by the direct beam was 
12, that acquired by three passages through the 
glass was 36, while that acquired by five passages 
was 60. But even when this method of magnifying 
was applied, he failed with various solid substances 
to obtain any effect ; and in the case of air, though 
he employed to the utmost the power which these re- 
peated reflections placed in his hands, he failed to 
produce the slightest sensible rotation. 

These failures of Faraday to obtain the effect with 


gases, seem to indicate the true seat of the phenome- 
non. The luniimferous ether surrounds and is influ- 
enced by the ultimate particles of matter. The symme- 
try of the one involves that of the other. Thus, if the 
molecules of a crystal be perfectly symmetrical round 
any line through the crystal, we may safely conclude 
that a ray will pass along this line as through ordi- 
nary glass. It will not be doubly refracted. Prom 
the symmetry of the liquid figures, known to be pro- 
duced in the planes of freezing, when radiant heat is 
sent through ice, we may safely infer symmetry of 
aggregation, and hence conclude that the line per- 
pendicular to the planes of freezing is a line of no 
double refraction : that it is, in fact, the optic axis of 
the crystal. The same remark applies to the line join- 
ing the opposite blunt angles of a crystal of Iceland 
spar. The arrangement of the molecules round this 
line being symmetrical, the condition of the ether de- 
pending upon these molecules shares their symmetry; 
and there is, therefore, no reason why the wave- 
length should alter with the alteration of the azi- 
muth round this line. Annealed glass has its mole- 
cules symmetrically arranged round every line that 
can be drawn through it ; hence it is not doubly re- 
fractive. But let the substance be either squeezed or 
strained in one direction, the molecular symmetry, and 
with it the symmetry of the ether, is immediately 


destroyed and the glass becomes doubly refractive. 
Unequal .heating produces the same effect. Thus 
mechanical strains reveal themselves by optical 
effects 5 and there is little doubt that in Faraday's 
experiment it is the magnetic strain that produces 
the rotation of the plane of polarization.* 


Faraday's next great step in discovery was an- 
nounced in a memoir on the c Magnetic Condition 
of all Matter,' communicated to the Royal Society 
on December 18, 1845. One great source of his 
success was the employment of extraordinary power. 
As already stated, he never accepted a negative 
answer to an experiment until he had brought to 
bear upon it all the force at his command. He had 
over and over again tried steel magnets and ordinary 

* The power of double refraction conferred on the centre of a glass 
rod, when it is caused to sound the fundamental note due to its longi- 
tudinal vibration, and the absence of the same power in the case of 
vibrating air (enclosed in a glass organ-pipe), seems to be analogous to 
the presence and absence of Faraday's effect in the same two substances. 

Faraday never, to my knowledge, attempted to give, even in conver- 
sation, a picture of the molecular condition of his heavy glass when 
subjected to magnetic influence. In a mathematical investigation of 
the subject, published in the Proceedings of the Royal Society for 1856, 
Sir William Thomson arrives at the conclusion that the ' diamagnetic ' 
is in a state of molecular rotation. 


electro-magnets on various substances, but without 
detecting anything different from the ordinary at- 
traction exhibited by a few of them. Stronger coer- 
cion, however, developed a new action. Before the 
pole of an electro-magnet, he suspended a frag- 
ment of his famous heavy glass ; and observed that 
when the magnet was powerfully excited the glass 
fairly retreated from the pole. It was a clear case 
of magnetic repulsion. He then suspended a bar of 
the glass between two poles ; the bar retreated when 
the poles were excited, and set its length equatorially 
or at right angles to the line joining them. When 
an ordinary magnetic body was similarly suspended, 
it always set axially, that is, from pole to pole. 

Faraday called those bodies which were repelled 
by the poles of a magnet, diamagnetic bodies ; using 
this term in asense different from that in which he 
employed it in his memoir on the magnetization of 
light. The term magnetic he reserved for bodies 
which exhibited the ordinary attraction. He after- 
wards employed the term magnetic to cover the whole 
phenomena of attraction and repulsion, and used the 
word paramagnetic to designate such magnetic action 
as is exhibited by iron. 

Isolated observations by Brugmanns, Becquerel, le 
Baillif, Saigy, and Seebeck, had indicated the exist- 
ence of a repulsive force exercised by the magnet on 


two or three substances ; but these observations, 
which were unknown to Faraday, had been permitted 
to remain without extension or examination. Having 
laid hold of the fact of repulsion, Faraday imme- 
diately expanded and multiplied it. He subjected 
bodies of the most various qualities to the action of 
his magnet: mineral salts, acids, alkalis, ethers, 
alcohols, aqueous solutions, glass, phosphorus, resins, 
oils, essences, vegetable and animal tissues, and 
found them all amenable to magnetic influence. No 
known solid or liquid proved insensible to the mag- 
netic power when developed in sufficient strength. 
All the tissues of the human body, the blood though 
it contains iron included, were proved to be dia- 
magnetic. So that if you could suspend a man 
between the poles of a magnet, his extremities would 
retreat from the poles until his length became equa- 

Soon after he had commenced his researches on 
diamagnetism, Faraday noticed a remarkable phe- 
nomenon which first crossed my own path in the 
following way : In the year 1849, while working in 
the cabinet of my friend, Professor Knoblauch, of 
Marburg, I suspended a small copper com between 
the poles of an electro-magnet. On exciting the 
magnet, the coin moved towards the poles and then 
suddenly stopped, as if it had struck against a 


cushion. On breaking the circuit, the coin was re- 
pelled, the revulsion being so violent as to cause it 
to spin several times round its axis of suspension. 
A Silber-groschen similarly suspended exhibited the 
same deportment. For a moment I thought this a 
new discovery ; but on looking over the literature of 
the subject, it appeared that Faraday had observed, 
multiplied, and explained the same effect during 
his researches on diamagnetism. His explanation 
was based upon his own great discovery of magneto- 
electric currents. The effect is a most singular 
one. A weight of several pounds of copper may be 
set spinning between the electro-magnetic poles ; 
the excitement of the magnet instantly stops the 
rotation. Though nothing is apparent to the eye, 
the copper, if moved in the excited magnetic field, 
appears to move through a viscous fluid ; while, when 
a flat piece of the metal is caused to pass to and fro 
like a saw between the poles, the sawing of the mag- 
netic field resembles the cutting through of cheese or 
butter.* This virtual friction of the magnetic field 
is so strong, that copper, by its rapid rotation between 
the poles, might probably be fused. We may easily 
dismiss this experiment by saying that the heat is 
due to the electric currents excited in the copper. 
But so long as we are unable to reply to the question, 

* See Heat as a Mode of Motion, third edition, 36. 


'What is an electric current?' the explanation is 
only provisional. For my own part, I look with 
profound interest and hope on the strange action 
here referred to. 

Faraday's thoughts ran intuitively into experi- 
mental combinations, so that subjects whose capacity 
for experimental treatment would, to ordinary minds, 
seem to be exhausted in a moment, were shown by 
him to be all but inexhaustible. He has now an 
object in view, the first step towards which is the 
proof that the principle of Archimedes is true of 
magnetism. He forms magnetic solutions of various 
degrees of strength, places them between the poles 
of his magnet, and suspends in the solutions various 
magnetic bodies. He proves that when the solution 
is stronger than the body plunged in it, the body, 
though magnetic, is repelled ; and when an elongated 
piece of it is surrounded by the solution it sets, like 
a diamagnetic body, equatorially between the excited 
poles. The same body when suspended in a solution 
of weaker magnetic power than itself, is attracted as 
whole, while an elongated portion of it sets axially. 

And now theoretic questions rush in upon him. 
Is this new force a true repulsion, or is it merely a 
differential attraction ? Might not the apparent re- 
pulsion of diamagnetic bodies be really due to the 
greater attraction of the medium by which they are 


surrounded? He tries the rarefaction of air, but 
finds the effect insensible. He is averse to ascribing 
a capacity of attraction to space, or to any hypothe- 
tical medium supposed to fill space. He therefore 
inclines, but still with caution, to the opinion that 
the action of a magnet upon bismuth is a true and 
absolute repulsion, and not merely the result of dif- 
ferential attraction. And then he clearly states a 
theoretic view sufficient to account for the pheno- 
mena. ' Theoretically,' he says, ' an explanation of 
the movements of the diamagnetic bodies, and all 
the dynamic phenomena consequent upon the action 
of magnets upon them, might be offered in the sup- 
position that magnetic induction caused in them a 
contrary state to that which it produced in ordinary 
matter.' That is to say, while in ordinary magnetic 
influence the exciting pole excites adjacent to itself 
the contrary magnetism, in diamagnetic bodies the 
adjacent magnetism is the same as that of the 
exciting pole. This theory of reversed polarity, 
however, does not appear to have ever laid deep 
hold of Faraday's mind ; and his own experiments 
failed to give any evidence of its truth. He there- 
fore subsequently abandoned it, and maintained the 
non-polarity of the diamagnetic force. 

He then entered a new, though related field of in- 
quiry. Having dealt with the metals and their coin- 


pounds, and having classified all of them that came 
within the range of his observation under the two 
heads magnetic and diamagnetic, he began the in- 
vestigation of the phenomena presented by crystals 
when subjected to magnetic power. The action of 
crystals had been in part theoretically predicted by 
Poisson,* and actually discovered by Pliicker, whose 
beautiful results, at the period which we have now 
reached, profoundly interested all scientific men. 
Faraday had been frequently puzzled by the deport- 
ment of bismuth, a highly crystalline metal. Some- 
times elongated masses of the substance refused to 
set equatorially, sometimes they set persistently ob- 
lique, and sometimes even, like a magnetic body, 
from, pole to pole. e The eifect,' he says, ' occurs 
at a single pole ; and it is then striking to observe 
a long piece of a substance so diamagnetic as bismuth 
repelled, and yet at the same moment set round with 
force, axially, or end on, as a piece of magnetic sub- 
stance would do.' The effect perplexed him ; and 
in his efforts to release himself from this perplexity, 
no feature of this new manifestation of force escaped 
his attention. His experiments are described in a 
memoir communicated to the Royal Society on De- 
cember 7, 1848. 

I have worked long myself at magne-crystallic 

* See Sir Wm. Thomson on Magne-crystallic Action. Phil. Mag. 1851. 


action, amid all the light of Faraday's and Pliicker s 
researches. The papers now before me were objects 
of daily and nightly study with me eighteen or nine- 
teen years ago ; but even now, though their perusal 
is but the last of a series of repetitions, they astonish 
me. Every circumstance connected with the sub- 
ject; every shade of deportment; every variation in 
the energy of the action ; almost every application 
which could possibly be made of magnetism to bring 
out in detail the character of this new force., is 
minutely described. The field is swept clean, and 
hardly anything experimental is left for the gleaner. 
The phenomena, he concludes, are altogether dif- 
ferent from those of magnetism or diamagnetism : 
they would appear, in fact, to present to us c a new 
force, or a new form of force, in the molecules of 
matter,' which, for convenience sake, he designates 
by a new word, as ' the magne-crystallic force.' 

He looks at the crystal acted upon by the -magnet. 
From its mass he passes, in idea, to its atoms, and he 
asks himself whether the power which can thus seize 
upon the crystalline molecules, after they have been 
fixed in their proper positions by crystallizing force, 
may not, when they are free, be able to determine 
their arrangement 9 He, therefore, liberates the 
atoms by fusing the bismuth. He places the fused 
substance between the poles of an electro-magnet, 


powerfully excited ; but lie fails to detect any action. 
I think it cannot be doubted that an action is exerted 
here, that a true cause comes into play : but its mag- 
nitude is not such as sensibly to interfere with the 
force of crystallization, which, in comparison with 
the diamagnetic force, is enormous. ' Perhaps,' adds 
Faraday, ' if a longer time were allowed, and a per- 
manent magnet used, a better result might be ob- 
tained. I had built many hopes upon the process.' 
This expression, and his writings abound in such, il- 
lustrates what has been already said regarding his ex- 
periments being suggested and guided by his theoretic 
conceptions. His mind was full of hopes and hypo- 
theses, but he always brought them to an experi- 
mental test. The record of his planned and executed 
experiments would, I doubt not, show a high ratio 
of hopes disappointed to hopes fulfilled ; but every 
case of fulfilment abolished all memory of defeat; 
disappointment was swallowed up in victory. 

After the description of the general character of 
this new force, Faraday states with the emphasis 
here reproduced its mode of action : ' The law of 
action appears to be that the line or axis of MAGNE- 
CETSTALLIC force (being the resultant of the action of 
all the molecules) tends to place itself parallel, or as a 
tangent, to the magnetic curve, or line of magnetic force, 
passing through the place where the crystal is situated. 9 



The magne-crystallic force, moreover, appears to 
him ' to be clearly distinguished from the magnetic 
or diamagnetic forces, in that it causes neither 
approach nor recession, consisting not in attraction 
or repulsion, but in giving a certain determinate 
position to the mass under its influence.' And then 
he goes on ' very carefully to examine and prove the 
conclusion that there was no connection of the force 
with attractive or repulsive influences.' With the 
most refined ingenuity he shows that, under certain 
circumstances, the magne-crystallic force can cause 
the centre of gravity of a highly magnetic body to 
retreat from the poles, and the centre of gravity of a 
highly diamagnetic body to approach them. His 
experiments root his mind more and more firmly in 
the conclusion that it is c neither attraction nor re- 
pulsion causes the set, or governs the final position ' 
of the crystal in the magnetic field. That the force 
which does so is therefore ' distinct in its character 
and effects from the magnetic and diamagnetic forms 
of force. On the other hand,' he continues, ' it has 
a most manifest relation to the crystalline structure 
of bismuth and other bodies, and therefore to the 
power by which their molecules are able to build up 
the crystalline masses.' 

And here follows one of those expressions which 
characterize the conceptions of Faraday in regard to 


force generally : c It appears to me impossible to 
conceive of the results in any other way than by a 
mutual reaction of the magnetic force, and the force 
of the particles of the crystal upon each other.' He 
proves that the action of the force, though thus 
molecular, is an action at a distance ; he shows that 
a bismuth crystal can cause a freely suspended mag- 
netic needle to set parallel to its magne-crystallic 
axis. Few living men are aware of the difficulty of 
obtaining results like this, or of the delicacy neces- 
sary to their attainment. ' But though it thus takes 
up the character of a force acting at a distance, still 
it is due to that power of the particles which makes 
them cohere in regular order and gives the mass its 
crystalline aggregation, which we call at other times 
the attraction of aggregation, and so often speak of 
as acting at insensible distances.' Thus he broods 
over this new force, and looks at it from all possible 
points of inspection. Experiment follows experiment, 
as thought follows thought. He will not relinquish 
the subject as long as a hope exists of throwing more 
light upon it. He knows full well the anomalous 
nature of the conclusion to which his experiments 
lead him. But experiment to him is final, and he 
will not shrink from the conclusion. ' This force,' 
he says, 6 appears to me to be very strange and 
striking in its character. It is not polar, for there 

H 2 


is no attraction or repulsion. 5 And then, as if startled 
by his own utterance, he asks ( What is the nature 
of the mechanical force which turns the crystal 
round, and makes it affect a magnet ? ' . , . i I 
do not remember,' he continues, f heretofore such a 
case of force as the present one, where a body is 
brought into position only, without attraction or re- 

Pliicker, the celebrated geometer already men- 
tioned, who pursued experimental physics for many 
years of his life with singular devotion and suc- 
cess, visited Faraday in those days, and repeated 
before him his beautiful experiments on magneto- 
optic action. Faraday repeated and verified Pliicker's 
observations, and concluded, what he at first seemed 
to doubt, that Pliicker's results and magne-crystallic 
action had the same origin. 

At the end of his papers, when he takes a last look 
along the line of research, and then turns his eyes to 
the future, utterances quite as much emotional as 
scientific escape from Faraday. ' I cannot,' he says, 
at the end of his first paper on magne-crystallic 
action, ' conclude this series of researches without 
remarking how rapidly the knowledge of molecular 
forces grows upon us, and how strikingly every in- 
vestigation tends to develop more and more their 
importance, and their extreme attraction as an object 


of study. A few years ago magnetism was to us an 
occult power, affecting only a few bodies, now it is 
found to influence all bodies, and to possess the most 
intimate relations with electricity, heat, chemical 
action, light, crystallization, and through it, with the 
forces concerned in cohesion; and we may, in the 
present state of things, well feel urged to continue in 
our labours, encouraged by the hope of bringing it 
into a bond of union with gravity itself.' 


A brief space will, perhaps, be granted me here to 
state the further progress of an investigation which 
interested Faraday so much. Drawn by the fame of 
Bunsen as a teacher, in the year 1848 I became a 
student in the University of Marburg, in Hesse Cassel. 
Bunsen behaved to me as a brother as well as a 
teacher, and it was also my happiness to make the 
acquaintance and gain the friendship of Professor 
Knoblauch, so highly distinguished by his researches 
on Eadiant Heat. Pliicker's and Faraday's investi- 
gations filled all minds at the time, and towards the 
end of 1849, Professor Knoblauch and myself com- 
menced a joint investigation of the entire question. 
Long discipline was necessary to give us due mastery 
over it. Employing a method proposed by Dove, we 


examined the optical properties of our crystals our- 
selves ; and these optical observations went hand in 
hand with our magnetic experiments. The number of 
these experiments was very great, but for a consider- 
able time no fact of importance was added to those 
already published At length, however, it was our 
fortune to meet with various crystals whose deport- 
ment could not be brought under the laws of magne- 
crystallic action enunciated by Pliicker. We also 
discovered instances which led us to suppose that the 
magne-crystallic force was by no means independent, 
as alleged, of the magnetism or diamagnetism of the 
mass of the crystal. Indeed, the more we worked at 
the subject, the more clearly did it appear to us that 
the deportment of crystals in the magnetic field was 
due, not to a force previously unknown, but to the 
modification of the known forces of magnetism and 
diamagnetism by crystalline aggregation. 

An eminent example of magne-crystallic action ad- 
duced by Pliicker and experimented on by Faraday, 
was Iceland spar. It is what in optics is called a 
negative crystal, and according to the law of Pliicker, 
the axis of such a crystal was always repelled by a 
magnet. But we showed that it was only necessary 
to substitute, in whole or in part, carbonate of iron 
for carbonate of lime, thus changing the magnetic, 
but not the optical character of the crystal, to cause 


the axis to be attracted. That the deportment of 
magnetic crystals is exactly antithetical to that of 
dianiagnetie crystals isomorphous with the magnetic 
ones, was proved to be a general law of action. In 
all cases, the line which in a diamagrietic-crystal set 
equatorially, always set itself in an isomorphous mag- 
netic crystal axially. By mechanical compression 
other bodies were also made to imitate the Iceland 

These and numerous other results bearing upon 
the question were published at the time in the c Phi- 
losophical Magazine ' and in 'Poggendoff's Annalen; ' 
and the investigation of diamagnetism and magne- 
crystallic action was subsequently continued by me 
in the laboratory of Professor Magnus of Berlin. In 
December, 1851, after I had quitted Germany, Dr. 
Bence Jones went to the Prussian capital to see the 
celebrated experiments of Du Bois Reymond ; and in- 
fluenced, I suppose, by what he heard, he afterwards 
invited me to give a Friday evening discourse at the 
Royal Institution. I consented, not without fear and 
trembling. For the Royal Institution was to me a kind 
of dragon's den, where tact and strength would be 
necessary to save me from destruction. On February 
11, 1853, the discourse was given, and it ended hap- 
pily. I allude to these things, that I may mention 
that though my aim and object in that lecture was 


to subvert the notions both of Faraday and Pliicker, 
and to establish in opposition to their views what 
I regarded as the truth, it was very far from pro- 
ducing in Faraday either enmity or anger. At the 
conclusion of the lecture, he quitted his accustomed 
seat, crossed the theatre to the corner into which I 
had shrunk, shook me by the hand, and brought me 
back to the table. Once more, subsequently, and in 
connection with a related question, I ventured to 
diifer from him still more emphatically. It was 
done out of trust in the greatness of his character ; 
nor was the trust misplaced. He felt my public 
dissent from him; and it pained me afterwards to 
the quick to think that I had given him even mo- 
mentary annoyance. It was, however, only momen- 
tary. His soul was above all littleness and proof to 
all egotism. He was the same to me afterwards that 
he had been before; the very chance expression which 
led me to conclude that he felt my dissent, being one 
of kindness and affection. 

It required long subsequent effort to subdue the 
complications of magne-crystallic action, and to 
bring under the dominion of elementary principles 
the vast mass of facts which the experiments of 
Faraday and Pliicker had brought to light. It was 
proved by Eeich, Edmond Becquerel, and myself, 
that the condition of diamagnetic bodies, in virtue of 


which, they were repelled by the poles of a magnet, 
was excited in them by those poles ; that the strength 
of this, condition rose and fell with, and was propor- 
tional to, the strength of the acting magnet. It was 
not then any property possessed permanently by the 
bismuth, and which merely required the development 
of magnetism to act upon it, that caused the repul- 
sion ; for then the repulsion would have been simply 
proportional to the strength of the influencing mag- 
net, whereas experiment proved it to augment as the 
square of the strength. The capacity to be repelled 
was therefore not inherent in the bismuth, but in- 
duced. So far an identity of action was established 
between magnetic and diamagnetic bodies. After 
this the deportment of magnetic bodies, ' normal ' 
and ' abnormal'; crystalline, amorphous, and com- 
pressed, was compared with that of crystalline, 
amorphous, and compressed diamagnetic bodies ; and 
by a series of experiments, executed in the laboratory 
of this Institution, the most complete antithesis was 
established between magnetism and diamagnetism. 
This antithesis embraced the quality of polarity, -the 
theory of reversed polarity, first propounded by Fara- 
day, being proved to be true. The discussion of the 
question was very brisk. On the Continent Professor 
Wilhelm Weber was the ablest and most successful 
supporter of the doctrine of diamagnetic polarity; 


and it was with an apparatus, devised by him and 
constructed under his own superintendence, by Leyser 
of Leipzig, that the last demands of the opponents 
of diamagnetic polarity were satisfied. The es- 
tablishment of this point was absolutely necessary 
to the explanation of magne-crystallic action. 

With that admirable instinct which always guided 
him, Faraday had seen that it was possible, if not 
probable, that the diamagnetic force acts with dif- 
ferent degrees of intensity in different directions, 
through the mass of a crystal. In his studies 011 
electricity, he had sought an experimental reply to 
the question whether crystalline bodies had not dif- 
ferent specific inductive capacities in different direc- 
tions, but he failed to establish any difference of the 
kind. His first attempt to establish differences of 
diamagnetic action in different directions through 
bismuth, was also a failure ; but he must have felt 
this to be a point of cardinal importance, for he 
returned to the subject in 1850, and proved that 
bismuth was repelled with different degrees of force 
in different directions. It seemed as if the crystal 
were compounded of two diamagnetic bodies of dif- 
ferent strengths, the substance being more strongly 
repelled across the magne-crystallic axis than along 
it. The same result was obtained independently, and 
extended to various other bodies, magnetic as well as 


diamagnetic, and also to compressed substances, a 
little subsequently by myself. 

The law of action in relation to this point is, that 
in diamagnetic crystals, the line along which the 
repulsion is a maximum, sets equatorially in the 
magnetic field; while in magnetic crystals the line 
along which the attraction is a maximum sets from 
pole to pole. Faraday had said that the magne- 
crystallic force was neither attraction nor repulsion. 
Thus far he was right. It was neither taken singly, 
but it was both. By the combination of the doctrine 
of diamagnetic polarity with these differential at- 
tractions and repulsions, and by paying due regard 
to the character of the magnetic field, every fact 
brought to light in the domain of magne-crystallic 
action received complete explanation. The most 
perplexing of those facts were shown to result 
from the action of mechanical couples, which the 
proved polarity both of magnetism and diamagnetism 
brought into play. Indeed the thoroughness with 
which the experiments of Faraday were thus ex- 
plained, is the most striking possible demonstration 
of the marvellous precision with which they were 



When an experimental result was obtained by 
Faraday it was instantly enlarged by his imagina- 
tion. I am acquainted with no mind whose power 
and suddenness of expansion at the touch of new 
physical truth could be ranked with his. Sometimes 
I have compared the action of his experiments on 
his mind to that of highly combustible matter thrown 
into a furnace ; every fresh entry of fact was accom- 
panied by the immediate development of light and 
heat. The light, which was intellectual, enabled 
him to see far beyond the boundaries of the fact 
itself, and the heat, which was emotional, urged him 
to the conquest of this newly-revealed domain. But 
though the force of his imagination was enormous, 
he bridled it like a mighty rider, and never permitted 
his intellect to be overthrown. 

In virtue of the expansive power which his vivid 
imagination conferred upon him, he rose from the 
smallest beginnings to the grandest ends. Having 
heard from Zantedeschi that Bancalari had esta- 
blished the magnetism of flame, he repeated the 
experiments and augmented the results. He passed 
from flames to gases, examining and revealing their 
magnetic and diamagnetic powers ; and then he sud- 


denly rose from his bubbles of oxygen and nitrogen 
to the atmospheric envelope of the earth itself, and its 
relations to the great question of terrestrial magne- 
tism. The rapidity with which these ever-augment- 
ing thoughts assumed the form of experiments is 
unparalleled. His power in this respect is often best 
illustrated by his minor investigations, and, perhaps, 
by none more strikingly than by his paper ' On the 
Diamagnetic Condition of Mame and Gases,' pub- 
lished as a letter to Mr. Richard Taylor, in the 
' Philosophical Magazine ' for December, 1847. 
After verifying, varying, and expanding the re- 
sults of Bancalari, he submitted to examination 
heated air-currents, produced by platinum spirals 
placed in the magnetic field, and raised to incan- 
descence by electricity. He then examined the 
magnetic deportment of gases generally. Almost 
all of these gases are invisible ; but he must, never- 
theless, track them in their unseen courses. He 
could not effect this by mingling smoke with his 
gases, for the action of his magnet upon the smoke 
would have troubled his conclusions. He, therefore, 
' caught ' his gases in tubes, carried them out of the 
magnetic field, and made them reveal themselves at 
a distance from the magnet. 

Immersing one ' gas in another, he determined 
their differential action 5 results of the utmost beauty 


being thus arrived at. Perhaps the most impor- 
tant are those obtained with atmospheric air and 
its two constituents. Oxygen, in various media, 
was strongly attracted by the magnet ; in coal-gas, 
for example, it was powerfully magnetic, whereas ni- 
trogen was diamagnetic. Some of the effects obtained 
with oxygen in coal-gas were strikingly beautiful. 
When the fumes of chloride of ammonium (a diamag- 
netic substance) were mingled with the oxygen, the 
cloud of chloride behaved in a most singular manner. 
' The attraction of iron filings,' says Faraday, ' to 
a magnetic pole is not more striking than the ap- 
pearance presented by the oxygen under these cir- 

On observing this deportment the question imme- 
diately occurs to him, can we not separate the 
oxygen of the atmosphere from its nitrogen by mag- 
netic analysis? It is the perpetual occurrence of 
such questions that marks the great experimenter. 
The attempt to analyze atmospheric air by magnetic 
force proved a failure, like the previous attempt to 
influence crystallization by the magnet. The en- 
nornious comparative power of the force of crystal- 
lization was then assigned as a reason for the in- 
competence of the magnet to determine molecular 
arrangement ; in the present instance the magnetic 
analysis is opposed by the force of diffusion, which is 


also very strong comparatively. The same remark 
applies to, and is illustrated by, another experiment 
subsequently executed by Faraday. Water is dia- 
niagnetic, sulphate of iron strongly magnetic. He 
enclosed c a dilute solution of sulphate of iron in a 
tube, and placed the lower end of the tube between 
the poles of a powerful horseshoe magnet for days 
together, 3 but he could produce ' no concentration of 
the solution in the part near the magnet.' Here also 
the diffusibility of the salt was too powerful for the 
force brought against it. 

The experiment last referred to is recorded in a 
paper presented to the Eoyal Society on the 2nd 
August, 1850, in which he pursues the investigation of 
the magnetism of gases. Newton's observations on 
soap-bubbles were often referred to by Faraday. His 
delight in a soap-bubble was like that of a boy, and 
he often introduced them in his lectures, causing 
them, when filled with air, to float on invisible seas 
of carbonic acid, and otherwise employing them as a 
means of illustration. He now finds them exceed- 
ingly useful in his experiments on the magnetic con- 
dition of gases. A bubble of air in a magnetic field 
occupied by air was unaffected, save through the feeble 
repulsion of its envelope. A bubble of nitrogen, on 
the contrary, was repelled from the magnetic axis 
with a force far surpassing that of a bubble of air. 


The deportment of oxygen in air ' was very impres- 
sive, the bubble being pulled inward, or towards the 
axial line, sharply and suddenly, as if the oxygen 
were highly magnetic.' 

He next labours to establish the true magnetic 
zero, a problem not so easy as might at first 
sight be imagined. For the action of the magnet 
upon any gas, while surrounded by air, or any other 
gas, can only be differential; and if the experiment 
were made in vacuo, the action of the envelope, in 
this case necessarily of a certain thickness, would 
trouble the result. While dealing with this sub- 
ject, Faraday makes some noteworthy observations 
regarding space. In reference to the Torricellian 
vacuum, he says, ' Perhaps it is hardly necessary for 
me to state that I find both iron and bismuth in 
such vacua perfectly obedient to the magnet. From 
such experiments, and also from general observations 
and knowledge, it seems manifest that the lines of 
magnetic force can traverse pure space, just as gravi- 
tating force does, and as statical electrical forces do, 
and therefore space has a magnetic relation of its 
own, and one that we shall probably find hereafter 
to be of the utmost importance in natural phenomena. 
But this character of space is not of the same kind 
as that which, in relation to matter, we endeavour to 
express by the terms magnetic and diamagnetic. To 


confuse these together would be to confound space 
with matter, and to trouble all the conceptions by 
which we endeavour to understand and work out a 
progressively clearer view of the mode of action, and 
the laws of natural forces. It would be as if in 
gravitation or electric forces, one were to confound 
the particles acting on each other with the space 
across which they are acting, and would, I think, 
shut the door to advancement. Mere space cannot 
act as matter acts, even though the utmost latitude 
be allowed to the hypothesis of an ether ; and admit- 
ting that hypothesis, it would be a large additional 
assumption to suppose that the lines of magnetic 
force are vibrations carried on by it, whilst as yet we 
have no proof that time is required for their propa- 
gation, or in what respect they may, in general cha- 
racter, assimilate to or differ from the respective lines 
of gravitating, luminiferous, or electric forces.' 

Pure space he assumes to be the true magne- 
tic zero, but he pushes his inquiries to ascertain 
whether among material substances there may not 
be some which resemble space. If you follow his 
experiments, you will soon emerge into the light of 
his results. A torsion beam was suspended by a 
skein of cocoon silk ; at one end of the beam was 
fixed a cross-piece 1 J inches long. Tubes of exceed- 
ingly thin glass, filled with various gases, and herme- 



tically sealed, were suspended in pairs from the two 
ends of the cross-piece. The position of the rotating 
torsion-head was such that the two tubes were at 
opposite sides of, and equidistant from, the magnetic 
axis, that is to say from the line joining the two 
closely approximated polar points of an electro mag- 
net. His object was to compare the magnetic action 
of the gases in the two tubes. When one tube was 
filled with oxygen, and the other with nitrogen, on 
the supervention of the magnetic force, the oxygen 
was pulled towards the axis, the nitrogen being 
pushed out. By turning the torsion-head they could 
be restored to their primitive position of equidistance, 
where it is evident the action of the glass envelopes 
was annulled. The amount of torsion necessary 
to re-establish equi-distance expressed the magnetic 
difference of the substances compared. 

And then he compared oxygen with oxygen at 
different pressures. One of his tubes contained the 
gas at the pressure of 30 inches of mercury, another 
at a pressure of 15 inches of mercury, a third at a 
pressure of 10 inches, while a fourth was exhausted 
as far as a good air-pump renders exhaustion pos- 
sible. ( When the first of these was compared with 
the other three, the effect was most striking.' It 
was drawn towards the axis when the magnet was 
excited, the tube containing the rarer gas being 
apparently driven away, and the greater the differ- 


ence between the densities of the two gases, the 
greater was the energy of this action. 

And now observe his mode of reaching a material 
magnetic zero. When a bubble of nitrogen was 
exposed in air in the magnetic field, on the super- 
vention of the power, the bubble retreated from the 
magnet. A less acute observer would have set nitro- 
gen down as diamagnetic ; but Faraday knew that re- 
treat, in a medium composed in part of oxygen, might 
be due to the attraction of the latter gas, instead of 
to the repulsion of the gas immersed in it. But if 
nitrogen be really diamagnetic, then a bubble or bulb 
filled with the dense gas will overcome one filled 
with the rarer gas. From the cross-piece of his tor- 
sion-balance he suspended his bulbs of nitrogen, at 
equal distances from the magnetic axis, and found 
that the rarefaction, or the condensation of the gas 
in either of the bulbs had not the slightest influence. 
When the magnetic force was developed, the bulbs 
remained in their first position, even when one was 
filled with nitrogen, and the other as far as possible 
exhausted. Nitrogen, in fact, acted 'like space it- 
self ; ' it was neither magnetic nor diamagnetic. 

He cannot conveniently compare the paramagnetic 
force of oxygen with iron, in consequence of the 
exceeding magnetic intensity of the latter substance ; 
bat he does compare it with the sulphate of iron, 

I 2 


and finds that, bulk for bulk, oxygen is equally mag- 
netic with a solution of this substance in water 
* containing seventeen times the weight of the oxy- 
gen in crystallized proto- sulphate of iron, or 3 -4 times 
its weight of metallic iron in that state of combina- 
tion.' By its capability to deflect a fine glass fibre, 
he finds that the attraction of his bulb of oxygen, 
containing only 0*117 of a grain of the gas, at an 
average distance of more than an inch from the 
magnetic axis, is about equal to the gravitating 
force of the same amount of oxygen as expressed by 
its weight. 

These facts could not rest for an instant in the 
mind of Faraday without receiving that expansion to 
which I have already referred. ' It is hardly neces- 
sary,' he writes, c for me to say here that this oxygen 
cannot exist in the atmosphere exerting such a re- 
markable and high amount of magnetic force, with- 
out having a most important influence on the dis- 
position of the magnetism of the earth, as a planet ; 
especially, if it be remembered that its magnetic 
condition is greatly altered by variations of its 
density and by variations of its temperature. I think 
I see here the real cause of many of the variations 
of that force, which have been, and are now so care- 
fully watched on different parts of the surface of the 
globe. The daily variation, and the annual variation, 


both seem likely to come under it ; also very many 
of the irregular continual variations, which the pho- 
tographic process of record renders so beautifully 
manifest. If such expectations be confirmed, and 
the influence of the atmosphere be found able to 
produce results like these, then we shall probably 
find a new relation between the aurora borealis and 
the magnetism of the earth, namely, a relation esta- 
blished, more or less, through the air itself in con- 
nection with the space above it ; and even magnetic 
relations and variations, which are not as yet sus- 
pected, may be suggested and rendered manifest and 
measurable, in the further development of what I 
will venture to call Atmospheric Magnetism. I may 
be over-sanguine in these expectations, but as yet I 
am. sustained in them by the apparent reality, sim- 
plicity, and sufficiency of the cause assumed, as it at 
present appears to my mind. As soon as I have 
submitted these views to a close consideration, and 
the test of accordance with observation, and, where 
applicable, with experiments also, I will do myself 
the honour to bring them before the Royal Society.' 

Two elaborate memoirs are then devoted to the 
subject of Atmospheric Magnetism; the -first sent to 
the Royal Society on the 9th of October, and the 
second on the 19th of November, 1850. In these 
memoirs he discusses the effects of heat and cold 


upon the magnetism of the air, and the action on 
the magnetic needle, which must result from thermal 
changes. By the convergence and divergence of the 
lines of terrestrial magnetic force, he shows how the 
distribution of magnetism, in the earth's atmos- 
phere, is affected. He applies his results to the ex- 
planation of the Annual and of the Diurnal Variation : 
he also considers irregular variations, including the 
action of magnetic storms. He discusses, at length, 
the observations at St. Petersburg, Greenwich, Ho- 
barton, St. Helena, Toronto, and the Cape of Good 
Hope ; believing that the facts, revealed by his ex- 
periments, furnish the key to the variations observed 
at all these places. 

In the year 1851, I had the honour of an interview 
with Humboldt, in Berlin, and his parting words to 
me then were, c Tell Faraday that I entirely agree 
with him, and that he has, in my opinion, completely 
explained the variation of the declination.' Eminent 
men have since informed me that Humboldt was 
hasty in expressing this opinion. In fact, Faraday's 
memoirs on atmospheric magnetism lost much of 
their force perhaps too much through the impor- 
tant discovery of the relation of the variation of the 
declination to the number of the solar spots. But I 
agree with him and M. Edmond Becquerel, who 
worked independently at this subject, in thinking, 


that a body so magnetic as oxygen, swathing the 
earth, and subject to variations of temperature, diur- 
nal and annual, must affect the manifestations of 
terrestrial magnetism.* The air that stands upon a 
single square foot of the earth's surface is, according 
to Faraday, equivalent in magnetic force to 81601bs. 
of crystallized protosulphate of iron. Such a sub- 
stance cannot be absolutely neutral as regards the 
deportment of the magnetic needle. But Faraday's 
writings on this subject are so voluminous, and the 
theoretic points are so novel and intricate, that I 
shall postpone the complete analysis of these re- 
searches to a time when I can lay hold of them more 
completely than my other duties allow me to do now. 


The scientific picture of Faraday would not be com- 
plete without a reference to his speculative writings. 
On Friday, January 19, 1844, he opened the weekly 
evening-meetings of the Royal Institution by a dis- 
course entitled A speculation touching Electric 
Conduction and the nature of Matter.' In this dis- 
course he not only attempts the overthrow of Dalton's 
Theory of Atoms, but also the subversion of all ordi- 

* This persuasion has been greatly strengthened by the recent perusal 
of a paper by Mr. Baxendell. 


nary scientific ideas regarding the nature and rela- 
tions of Matter and Force. He objected to the use of 
the term atom : c I have not yet found a mind,' he 
says, c that did habitually separate it from its accom- 
panying temptations ; and there can be no doubt that 
the words definite proportions, equivalent, primes, 
&c., which did and do fully express all the fads of 
what is usually called the atomic theory in chemistry, 
were dismissed because they were not expressive 
enough, and did not say all that was in the mind of 
him who used the word atom in their stead.' 

A moment will be granted me to indicate my own 
view of Faraday's position here. The word c atom' 
was not used in the stead of definite proportions, 
equivalents, or primes. These terms represented 
facts that followed from, but were not equivalent 
to, the atomic theory. Facts cannot satisfy the 
mind : and the law of definite combining proportions 
being once established, the question 'why should 
combination take place according to that law ? ' is 
inevitable. Dalton answered this question by the 
enunciation of the Atomic Theory, the funda- 
mental idea of which is, in my opinion, per- 
fectly secure. The objection of Faraday to Dalton, 
might be urged with the same substantial force 
against Newton : it might be stated with regard to 
the planetary motions that the laws of Kepler re- 
vealed the fads ; that the introduction of the prin- 


ciple of gravitation was an addition to the facts. 
But this is the essence of all theory. The theory is 
the backward guess from fact to principle; the con- 
jecture, or divination regarding something, which 
lies behind the facts, and from which they flow in 
necessary sequence. If Dalton's theory, then, ac- 
count for the definite proportions observed in the 
combinations of chemistry, its justification rests upon 
the same basis as that of the principle of gravi- 
tation. All that can in strictness be said in either 
case is that the facts occur as if the principle 

The manner in which Faraday himself habitually 
deals with his hypotheses is revealed in this lecture. 
He incessantly employed them to gain experimental 
ends, but he incessantly took them down, as an ar- 
chitect removes the scaffolding when the edifice is 
complete. 'I cannot but doubt,' he says, ' that he who 
as a mere philosopher has most power of penetrating 
the secrets of nature, and guessing by hypothesis at 
her mode of working, will also be most careful for 
his own safe progress and that of others, to distin- 
guish the knowledge which consists of assumption, 
by which I mean theory and hypothesis, from that 
which is the knowledge of facts and laws.' Faraday 
himself, in fact, was always ' guessing by hypothesis,' 
and making theoretic divination the stepping-stone 
to his experimental results. 


I have already more than once dwelt on the vivid- 
ness with which he realised molecular conditions ; we 
have a fine example of this strength and brightness 
of imagination in the present ' speculation.' He 
grapples with the notion that matter is made up of 
particles, not in absolute contact, but surrounded 
by inter-atomic space. ' Space,' he observes, ' must 
be taken as the only continuous part of a body 
so constituted. Space will permeate all masses of 
matter in every direction like a net, except that in 
place of meshes it will form cells, isolating each atom 
from its neighbours, itself only being continuous.' 

Let us follow out this notion ; consider, he argues, 
the case of a non-conductor of electricity, such for 
example as shell-lac, with its molecules, and in- 
termolecular spaces running through the mass. In 
its case space must be an insulator ; for if it were a 
conductor it would resemble 'a fine metallic web,' pene- 
trating the lac in every direction. But the fact is that 
it resembles the wax of black sealing-wax, which sur- 
rounds and insulates the particles of conducting car- 
bon, interspersed throughout its mass. In the case of 
shell-lac, therefore, space is an insulator. 

But now, take the case of a conducting metal. Here 
we have as before, the swathing of space round every 
atom. If space be an insulator there can be no trans- 
mission of electricity from atom to atom. But there 


is transmission ; hence space is a conductor. Thus he 
endeavours to hamper the atomic theory. ' The rea- 
soning,' he says, 'ends in a subversion of that theory 
altogether ; for if space be an insulator it cannot exist 
in conducting bodies, and if it be a conductor it can- 
not exist in insulating bodies. Any ground of rea- 
soning,' he adds, as if carried away by the ardour of 
argument, ' which tends to such conclusions as these 
must in itself be false.' 

He then tosses the atomic theory from horn to horn 
of his dilemmas. What do we know, he asks, of the 
atom apart from its force ? You imagine a nucleus 
which may be called a, and surround it by forces 
which may be called m ; ' to my mind the a or nucleus 
vanishes, and the substance consists in the powers of 
m. And indeed what notion can we form of the 
nucleus independent of its powers ? What thought 
remains on which to hang the imagination of an a 
independent of the acknowledged forces? ' Like Bos- 
covich he abolishes the atom, and puts a ' centre of 
force ' in its place. 

With his usual courage and sincerity he pushes his 
view to its utmost consequences. * This view of the 
constitution of matter,' he continues, ' would seem to 
involve necessarily the conclusion that matter fills 
all space, or at least all space to which gravitation 
extends; for gravitation is a property of matter 


dependent on a certain force, and it is this force which 
constitutes the matter. In that view matter is not 
merely mutually penetrable ;* but each atom extends, 
so to say, throughout the whole of the solar system, 
yet always retaining its own centre of force.' 

It is the operation of a mind filled with thoughts 
of this profound, strange, and subtle character that 
we have to take into account in dealing with Fara- 
day's later researches. A similar cast of thought 
pervades a letter addressed by Faraday to Mr. Eichard 
Phillips, and published in the 'Philosophical Maga- 
zine' for May, 1846. It is entitled 'Thoughts on Ray- 
vibrations,' and it contains one of the most singular 
speculations that ever emanated from a scientific 
mind. It must be remembered here, that though 
Faraday lived amid such speculations he did not rate 
them highly, and that he was prepared at any mo- 
ment -to change them or let them go. They spurred 
him on, but they did not hamper him. His theo- 
retic notions were fluent ; and when minds less 
plastic than his own attempted to render those 
fluxional images rigid, he rebelled. He warns Phil- 
lips, moreover, that from first to last, 'he merely 
threw out as matter for speculation the vague im- 

* He compares the interpenetration of two atoms to the coalescence 
of two distinct waves, which though for a moment blended to a single 
mass, preserve their individuality, and afterwards separate. 


pressions of his mind; for he gave nothing as the 
result of sufficient consideration, or as the settled 
conviction, or even probable conclusion at which he 
had arrived.' 

The gist of this communication is that gravitating 
force acts in lines across space, and that the vibrations 
of light and radiant heat consist in the tremors of 
these lines of force. ' This notion,' he says, ' as far 
as it is admitted," will dispense with the ether, which, 
in another view, is supposed to be the medium in 
which these vibrations take place.' And he adds 
further on, that his view ' endeavours to dismiss 
the ether but not the vibrations.' The idea here 
set forth is the natural supplement of his previous 
notion, that it is gravitating force which constitutes 
matter, each atom extending, so to say, throughout 
the whole of the solar system. 

The letter to Mr. Phillips winds up with this beau- 
tiful conclusion : 

' I think it likely that I have made many mistakes 
in the preceding pages, for even to myself my ideas 
on this point appear only as the shadow of a specu- 
lation, or as one of those impressions upon the mind 
which are allowable for a time as guides to thought 
and research. He who labours in experimental 
inquiries, knows how numerous these are, and how 


often their apparent fitness and beauty vanish before 
the progress and development of real natural truth.' 

Let it then be remembered that Faraday entertained 
notions regarding matter and force altogether dis- 
tinct from the views generally held by scientific men. 
Force seemed to him an entity dwelling along the line 
in which it is exerted. The lines along which gra- 
vity acts between the sun and earth seem figured 
in his mind as so many elastic strings : indeed he 
accepts the assumed instantaneity of gravity as the 
expression of the enormous elasticity of the ' lines 
of weight.' Such views, fruitful in the case of 
magnetism, barren, as yet, in the case of gravity, 
explain his efforts to transform this latter force. 
When he goes into the open air and permits his 
helices to fall, to his mind's eye they are tearing 
through the lines of gravitating power, and hence 
his hope and conviction that an effect would and 
ought to be produced. It must ever be borne in 
mind that Faraday's difficulty in dealing with these 
conceptions was at bottom the same as that of 
Newton ; that he is in fact trying to overleap this 
difficulty, and with it probably the limits prescribed 
to the intellect itself. 

The idea of lines of magnetic force was sug- 
gested to Faraday by the linear arrangement of 


iron filings when scattered over a magnet. He 
speaks of and illustrates by sketches, the deflec- 
tion, both convergent and divergent, of the lines of 
force, when they pass respectively through magnetic 
and diamagnetic bodies. These notions of concen- 
tration and divergence are also based on the direct 
observation of his filings. So long did he brood upon 
these lines ; so habitually did he associate them with 
his experiments on induced currents, that the asso- 
ciation became e indissoluble,' and he could not think 
without them. ' I have been so accustomed/ he 
writes, ( to employ them, and especially in my last 
researches, that I may have unwittingly become pre- 
judiced in their favour, and ceased to be a clear- 
sighted judge. Still, I have always endeavoured to 
make experiment the test and controller of theory 
and opinion ; but neither by that nor by close cross- 
examination in principle, have I been made aware of 
any error involved in their use.' 

In his later researches on magne-crystallic action, 
the idea of lines of force is extensively employed ; it 
indeed led him to an experiment which lies at the 
root of the whole question. In his subsequent re- 
searches on Atmospheric Magnetism the idea receives 
still wider application, showing itself to be wonder- 
fully flexible and convenient. Indeed without this 
conception the attempt to seize upon the magnetic 


actions, possible or actual, of the atmosphere would 
be difficult in the extreme ; but the notion of lines of 
force, and of their divergence and convergence, guides 
Faraday without perplexity through all the intricacies 
of the question. After the completion of those re- 
searches, and in a paper forwarded to the Royal 
Society on October 22, 1851, he devotes himself to the 
formal development and illustration of his favour- 
ite idea. The paper bears the title, ( On lines of 
magnetic force, their definite character, and their 
distribution within a magnet and through space.' 
A deep reflectiveness is the characteristic of this 
memoir. In his experiments, which are perfectly 
beautiful and profoundly suggestive, he takes but a 
secondary delight. llis object is to illustrate the 
utility of his conception of lines of force. 'The 
study of these lines,' he says, ( has at different times 
been greatly influential in leading me to various 
results which I think prove their utility as well as 

Faraday for a long period used the lines of force 
merely as 'a representative idea.' He seemed for a 
time averse to going further in expression than the 
lines themselves, however much further he may 
have gone in idea. That he believed them to 
exist at all times round a magnet, and irrespec- 
tive of the existence of magnetic matter, such as 


iron filings, external to the magnet, is certain. 
No doubt the space round every magnet presented 
itself to his imagination as traversed by loops of 
magnetic power; but he was chary in speaking 
of the physical substratum of those loops. Indeed 
it may be doubted whether the physical theory of 
lines of force presented itself with any distinctness 
to his own mind. The possible complicity of the 
luminiferous ether in magnetic phenomena was cer- 
tainly in his thoughts. ' How the magnetic force,' 
he writes, ' is transferred through bodies or through 
space we know not ; whether the result is merely 
action at a distance, as in the case of gravity ; or by 
some intermediate agency, as in the case of light, 
heat, the electric current, and (as I believe) static 
electric action. The idea of magnetic fluids, as ap- 
plied by some, or of magnetic centres of action, does 
not include that of the latter kind of transmission, 
but the idea of lines of force does.' And he continues 
thus : ' I am more inclined to the notion that in the 
transmission of the [magnetic] force there is such 
an action [an intermediate agency] external to the 
magnet, than that the effects are merely attraction 
and repulsion at a distance. Such an affection may be 
a function of the ether j for it is not at all unlikely that, 
if there be an ether, it should have other uses than simply 
the conveyance of radiations. 9 When he speaks of the 


magnet in certain cases, ' revolving amongst its own 
forces/ he appears to have some conception of this 
kind in view. 

A great part of the investigation completed in 
October, 1851, was taken up with the motions of 
wires round the poles of a magnet and the converse. 
He carried an insulated wire along the axis of a 
bar magnet from its pole to its equator, where it 
issued from the magnet, and was bent up so as to 
connect its two ends. A complete circuit, no part of 
which was in contact with the magnet, was thus ob- 
tained. He found that when the magnet and the 
external wire were rotated together no current was 
produced ; whereas, when either of them was rotated 
and the other left at rest currents were evolved. 
He then abandoned the axial wire, and allowed the 
magnet itself to take its place ; the result was the 
same.* It was the relative motion of the magnet 
and the loop that was effectual in producing a cur- 

The lines of force have their roots in the magnet, 
and though they may expand into infinite space, 
they eventually return to the magnet. Now these 
lines may be intersected close to the magnet or at a 
distance from it. Faraday finds distance to be per- 

* In this form the experiment is identical with one made twenty 
years earlier. See page 30. 


fectly immaterial so long as the number of lines in- 
tersected is the same. For example, when the loop 
connecting the equator and the pole of his bar- 
inagnet performs one complete revolution round the 
magnet, it is manifest that all the lines of force issuing 
from the magnet are once intersected. Now it matters 
not whether the loop be ten feet or ten inches in 
length, it matters not how it may be twisted and 
contorted, it matters not how near to the magnet or 
how distant from it the loop may be, one revolution 
always produces the same amount of current elec- 
tricity, because in all these cases all the lines of force 
issuing from the magnet are once intersected and 
no more. 

From the external portion of the circuit he passes 
in idea to the internal, and follows the lines of force 
into the body of the magnet itself. His conclusion 
is that there exist lines of force within the magnet 
of the same nature as those without. What is more, 
they are exactly equal in amount to those without. 
They have a relation in direction to those without ; 
and in fact are continuations of them. . . * Every 
line of force, therefore, at whatever distance it may 
be taken from the magnet, must be considered as 
a closed circuit, passing in some part of its course 
through the magnet, and having an equal amount of 
force in every part of its course.' 

K 2 


All the results here described were obtained with 
moving metals. 'But,' he continues with profound 
sagacity, ' mere motion would not generate a relation, 
which had not a foundation in the existence of some 
previous state; and therefore the quiescent metals 
must be in some relation to the active centre of force,' 
that is to the magnet. He here touches the core of 
the whole question, and when we can state the con- 
dition into which the conducting wire is thrown 
before it is moved, we shall then be in a position to 
understand the physical constitution of the electric 
current generated by its motion. 

In this inquiry Faraday worked with steel magnets, 
the force of which varies with the distance from the 
magnet. He then sought a uniform field of magnetic 
force, and found it in space as affected by the magnet- 
ism of the earth. His next memoir, sent to the 
Royal Society, December 31, 1851, is c on the employ- 
ment of the Induced Magneto-electro Current as a 
test and measure of magnetic forces.' He forms 
rectangles and rings, and by ingenious and simple 
devices collects the opposed currents which are de- 
veloped in them by rotation across the terrestrial lines 
of magnetic force. He varies the shapes of his rec- 
tangles while preserving their areas constant, and 
finds that the constant area produces always the same 
amount of current per revolution. The current de- 


.pends solely on the number of lines of force inter- 
sected, and when this number is kept constant the 
current remains constant too. Thus the lines of mag- 
netic force are continually before his eyes, by their 
aid he colligates his facts, and through the inspira- 
tions derived from them he vastly expands the 
boundaries of our experimental knowledge. The 
beauty and exactitude of the results of this investi- 
gation are extraordinary. I cannot help thinking 
while I dwell upon them, that this discovery of mag- 
neto-electricity is the greatest experimental result 
ever obtained by an investigator. It is the Mont 
Blanc of Faraday's own achievements. He always 
worked at great elevations, but a higher than this 
he never subsequently attained. 


The terms unity and convertibility, as applied to 
natural forces, are often employed in these investi- 
gations, many profound and beautiful thoughts re- 
specting these subjects being expressed in Faraday's 
memoirs. Modern inquiry has, however, much aug- 
mented our knowledge of the relationship of natural 
forces, and it seems worth while to say a few words 
here, tending to clear up certain misconceptions 


which appear to exist among philosophic writers 
regarding this relationship. 

The whole stock of energy or working-power in the 
world consists of attractions, repulsions, and motions. 
If the attractions and repulsions are so circumstanced 
as to be able to produce motion, they are sources 
of working-power, but not otherwise. Let us for 
the sake of simplicity confine our attention to the 
case of attraction. The attraction exerted between 
the earth and a body at a distance from the earth's 
surface is a source of working-power ; because the 
body can be moved by the attraction, and in falling 
to the earth can perform work. When it rests upon 
the earth's surface it is not a source of power or 
energy, because it can fall no further. But though 
it has ceased to be a source of energy, the attraction 
of gravity still acts as & force, which holds the earth 
and weight together. 

The same remarks apply to attracting atoms and 
molecules. As long as distance separates them, they 
can move across it in obedience to the attraction, 
and the motion thus produced may, by proper appli- 
ances, be caused to perform mechanical work. 
When, for example, two atoms of hydrogen unite 
with one of oxygen, to form water, the atoms 
are first drawn towards each other they move, 
they clash, and then by virtue of their resiliency, 


they recoil and quiver. To this quivering motion 
we give the name of heat. Now this quivering 
motion is merely the redistribution of the motion 
produced by the chemical affinity ; and this is the only 
sense in which chemical affinity can be said to be 
converted into heat. We must not imagine the chemi- 
cal attraction destroyed, or converted into anything 
else. For the atoms, when mutually clasped to form 
a molecule of water, are held together by the very 
attraction which first drew them towards each other. 
That which has really been expended is the pull 
exerted through the space by which the distance 
between the atoms has been diminished. 

If this be understood, it will be at once seen tha,t 
gravity may in this sense be said to be convertible 
into heat ; that it is in reality no more an outstand- 
ing and inconvertible agent, as it is sometimes stated 
to be, than chemical affinity. By the exertion of a 
certain pull, through a certain space, a body is caused 
to clash with a certain definite velocity against the 
earth. Heat is thereby developed, and this is the 
only sense in which gravity can be said to be con- 
verted into heat. In no case is the force which pro- 
duces the motion annihilated or changed into any- 
thing else. The mutual attraction of the earth and 
weight exists when they are in contact as when they 
were separate ; but the ability of that attraction to 


employ itself in the production of motion does not 

The transformation, in this case, is easily followed 
by the mind's eye. First, the weight as a whole is 
set in motion by the attraction of gravity. This 
motion of the mass is arrested by collision with the 
earth; being broken up into molecular tremors, to 
which we give the name of heat. 

And when we reverse the process, and employ 
those tremors of heat to raise a weight, as is done 
through the intermediation of an elastic fluid in the 
steam-engine, a certain definite portion of the mole- 
cular motion is destroyed in raising the weight. In 
this sense, and this sense only, can the heat be said 
to be converted into gravity, or more correctly, into 
potential energy of gravity. It is not that the de- 
struction of the heat has created any new attraction, 
but simply that the old attraction has now a power 
conferred upon it, of exerting a certain definite pull 
in the interval between the starting-point of the 
falling weight and its collision with the earth. 

So also as regards magnetic attraction : when a 
sphere of iron placed at some distance from a mag- 
net rushes towards the magnet, and has its motion 
stopped by collision, an effect mechanically the same 
as that produced by the attraction of gravity occurs. 
The magnetic attraction generates the motion of the 


mass, and the stoppage of that motion produces heat. 
In this sense, and in this sense only, is there a trans- 
formation of magnetic work into heat. And if by 
the mechanical action of heat, brought to bear by 
means of a suitable machine, the sphere be torn from 
the magnet and again placed at a distance, a power 
of exerting a pull through that distance, and produc- 
ing a new motion of the sphere, is thereby conferred 
upon the magnet; in this sense, and in this sense 
only, is the heat converted into magnetic potential 

When, therefore, writers on the conservation of 
energy speak of tensions being ' consumed ' and 
' generated,' they do not mean thereby that old 
attractions have been annihilated and new ones 
brought into existence, but that, in the one case, 
the power of the attraction to produce motion has 
been diminished by the shortening of the distance 
between the attracting bodies, and that in the other 
case the power of producing motion has been aug- 
mented by the increase of the distance. These re- 
marks apply to all bodies, whether they be sensible 
masses or molecules. 

Of the inner quality that enables matter to attract 
matter we know nothing ; and the law of conserva- 
tion makes no statement regarding that quality. 
It takes the facts of attraction as they stand, and 


affirms only the constancy of working-power. That 
power may exist in the form of MOTION ; or it may 
exist in the form of FORCE, with distance to act 
through. The former is dynamic energy, the latter 
is potential energy, the constancy of the sum of both 
being affirmed by the law of conservation. The con- 
vertibility of natural forces consists solely in trans- 
formations of dynamic into potential, and of potential 
into dynamic, energy, which are incessantly going 
on. In no other sense has the convertibility of force, 
at present, any scientific meaning. 

By the contraction of a muscle a man lifts a 
weight from the earth. But the muscle can con- 
tract only through the oxidation of its own tissue or 
of the blood passing through it. Molecular motion 
is thus converted into mechanical motion. Supposing 
the muscle to contract without raising the weight, 
oxidation would also occur, but the whole of the heat 
produced by this oxidation would be liberated in the 
muscle itself. Not so when it performs external work ; 
to do that work a certain definite portion of the heat 
of oxidation must be expended. It is so expended 
in pulling the weight away from the earth. If the 
weight be permitted to fall, the heat generated by its 
collision with the earth would exactly make up for 
that lacking in the muscle during the lifting of the 
weight. In the case here supposed, we have a con- 


version of molecular muscular action into potential 
energy of gravity ; and a conversion of that potential 
energy into heat; the heat, however, appearing at 
a distance from its real origin in the muscle. The 
whole process consists of a transference of molecular 
motion from the muscle to the weight, and gravitat- 
ing force is the mere go-between, by means of which 
the transference is effected. 

These considerations will help to clear our way to 
the conception of the transformations which occur 
when a wire is moved across the lines of force in a 
magnetic field. In this case it is commonly said we 
have a conversion of magnetism into electricity. But 
let us endeavour to understand what really occurs. 
For the sake of simplicity, and with a view to its 
translation into a different one subsequently, let us 
adopt for a moment the provisional conception of a 
mixed fluid in the wire, composed of positive and 
negative electricities in equal quantities, and there- 
fore perfectly neutralizing each other when the wire 
is still. By the motion of the wire, say with the 
hand, towards the magnet, what the Germans call a 
Scheidungs-Kraft a separating force is brought into 
play. This force tears the mixed fluids asunder, and 
drives them in two currents, the one positive and 
the other negative, in two opposite directions through 
the wire. The presence of these currents evokes a 


force of repulsion between the magnet and the wire ; 
and to cause the one to approach the other, this re- 
pulsion must be overcome. The overcoming of this 
repulsion is, in fact, the work done in separating and 
impelling the two electricities. When the wire is 
moved away from the magnet, a Scheidungs-Kraft, or 
separating force, also comes into play ; but now it is 
an attraction that has to be surmounted. In sur- 
mounting it, currents are developed in directions 
opposed to the former ; positive takes the place of 
negative, and negative the place of positive ; the over- 
coming of the attraction being the work done in sepa- 
rating and impelling the two electricities. 

The mechanical action occurring here is different 
from that occurring where a sphere of soft iron is 
withdrawn from a magnet, and again attracted. 
In this case muscular force is expended during the 
act of separation ; but the attraction of the magnet 
effects the reunion. In the case of the moving wire 
also we overcome a resistance in separating it from 
the magnet, and thus far the action is mechanically 
the same as the separation of the sphere of iron. 
But after the wire has ceased moving, the attraction 
ceases ; and so far from any action occurring similar 
to that, which draws the iron sphere back to the 
magnet, we have to overcome a repulsion to bring 
them together. 


There is no potential energy conferred either by 
the removal or by the approach of the wire, and the 
only power really transformed or converted, in the 
experiment, is muscular power. Nothing that could 
in strictness be called a conversion of magnetism 
into electricity occurs. The muscular oxidation that 
moves the wire fails to produce within the imiscle its 
due amount of heat, a portion of that heat equi- 
valent to the resistance overcome, appearing in the 
moving wire instead. 

Is this effect an attraction and a repulsion at a 
distance? If so, why should both cease when the 
wire ceases to move? In fact, the deportment 
of the wire resembles far more that of a body 
moving in a resisting medium than anything else ; 
the resistance ceasing when the motion is sus- 
pended. Let us imagine the case of a liquid so 
mobile that the hand may be passed through it to 
and fro, without encountering any sensible re- 
sistance. It resembles the motion of a conductor in 
the unexcited field of an electro-magnet. Now, let 
us suppose a body placed in the liquid, or acting on 
it, which confers upon it the property of viscosity ; 
the hand would no longer move freely. During its 
motion, but then only, resistance would be encoun- 
tered and overcome. Here we have rudely repre- 
sented the case of the excited magnetic field, and the 


result in both, cases would be substantially the same. 
In both cases heat would, in the end, be generated 
outside of the muscle, its amount being exactly 
equivalent to the resistance overcome. 

Let us push the analogy a little further ; suppose 
in the case of the fluid rendered viscous, as assumed 
a moment ago, the viscosity not to be so great as to 
prevent the formation of ripples when the hand is 
passed through the liquid. Then the motion of the 
hand, before its final conversion into heat, would 
exist for a time as wave-motion, which, on subsiding, 
would generate its due equivalent of heat. This in- 
termediate stage, in the case of our moving wire, is 
represented by the period during which the electric 
current is flowing through it ; but that current, like 
the ripples of our liquid, soon subsides, being, like 
them, converted into heat. 

Do these words shadow forth anything like the 
reality? Such speculations cannot be injurious if 
they are enunciated without dogmatism. I do con- 
fess that ideas such as these here indicated exercise 
a strong fascination on my mind. Is then the 
magnetic field really viscous, and if so, what sub- 
stance exists in it and the wire to produce the visco- 
sity? Let us first look at the proved effects, and 
afterwards turn our thoughts back upon their cause. 


When the wire approaches the magnet, an action is 
evoked within it, which travels through it with a 
velocity comparable to that of light. One substance 
only in the universe has been hitherto proved compe* 
tent to transmit power at this velocity ; the lumini- 
ferous ether. Not only its rapidity of progression but 
its ability to produce the motion of light and heat, 
indicates that the electric current is also motion.* 
Further, there is a striking resemblance between the 
action of good and bad conductors as regards electri- 
city, and the action of diathermanous and adiather- 
manous bodies as regards radiant heat. The good 
conductor is diathermanous to the electric current ; it 
allows free transmission without the development of 
heat. The bad conductor is adiathermanous to the 
electric current, and hence the passage of the latter 
is accompanied by the development of heat. I am 
strongly inclined to hold the electric current, pure 
and simple, to be a motion of the ether alone ; good 
conductors being so constituted that the motion may 
be propagated through their ether without sensible 
transfer to their atoms, while in the case of bad 

* Mr. Clerk Maxwell has recently published an exceedingly im- 
portant investigation connected with this question. Even in the non- 
mathematical portions of the memoirs of Mr. Maxwell, the admirable 
spirit of his philosophy is sufficiently revealed. As regards the em- 
ployment of scientific imagery, I hardly know his equal in power of 
conception and clearness of definition. 


conductors this transfer is effected, the transferred 
motion appearing as heat.* 

I do not know whether Faraday would have sub- 
scribed to what is here written; probably his habitual 
caution would have prevented him from committing 
himself to anything so definite. But some such 
idea filled his mind and coloured his language 
through all the later years of his life. I dare not say 
that he has been always successful in the treatment 
of these theoretic notions. In his speculations he 
mixes together light and darkness in varying pro- 
portions, and carries us along with him through 
strong alternations of both. It is impossible to 
say how a certain amount of mathematical train- 
ing would have affected his work. We cannot say 
what its influence would have been upon that force 
of inspiration that urged him on ; whether it would 
have daunted him, and prevented him from driving 
his adits into places, where no theory pointed to a 
lode. If so, then we may rejoice that this strong 
delver at the mine of natural knowledge was left free 
to wield his mattock in his own way. It must be 
admitted, that Faraday's purely speculative writings 
often lack that precision which the mathematical 

* One important difference, of course, exists between the effect of 
motion in the magnetic field, and motion in a resisting medium. In the 
former case the heat is generated in the moving conductor, in the latter 
it is in part generated in the medium. 


habit of thought confers. Still across them flash 
frequent gleams of prescient wisdom which will ex- 
cite admiration throughout all time ; while the facts, 
relations, principles, and laws which his experiments 
have established are sure to form the body of grand 
theories yet to come. 


When from an Alpine height the eye of the 
climber ranges over the mountains, he finds that for 
the most part they resolve themselves into distinct 
groups, each consisting of a dominant mass sur- 
rounded by peaks of lesser elevation. The power 
which lifted the mightier eminences, in nearly all 
cases lifted others to an almost equal height. And 
so it is with the discoveries of Faraday. As a 
general rule, the dominant result does not stand 
alone, but forms the culminating point of a vast and 
varied mass of inquiry. In this way, round about his 
great discovery of Magneto-electric Induction, other 
weighty labours group themselves. His investi- 
gations on the Extra Current; on the Polar and 
other Condition of Diamagnetic Bodies ; on Lines of 
Magnetic Force, their definite character and distri- 
bution ; on the employment of the Induced Magneto- 
electric Current as a measure and test of Magnetic 
Action ; on the Eevulsive Phenomena of the mag- 



netic field, are all, notwithstanding the diversity of 
title, researches in the domain of Magneto-electric 

Faraday's second group of researches and dis- 
coveries embrace the chemical phenomena of the 
current. The dominant result here is the great law 
of definite Electro-chemical Decomposition, around 
which are massed various researches on Electro- 
chemical Conduction, and on Electrolysis both with 
the Machine and with the Pile. To this group also 
belong his analysis of the Contact Theory, his 
inquiries as to the Source of Yoltaic Electricity, and 
his final development of the Chemical Theory of 
the pile. 

His third great discovery is the Magnetization 
of Light, which I should liken to the Weisshorn 
among mountains high, beautiful, and alone. 

The dominant result of his fourth group of re- 
searches is the discovery of Diamagnetism, an- 
nounced in his memoir as the Magnetic Condition of 
all Matter, round which are grouped his inquiries on 
the Magnetism of Flame and Gases; on Magne- 
crystallic action, and on Atmospheric Magnetism, 
in its relations to the annual and diurnal variation of 
the needle, the full significance of which is still to be 

These are Faraday's most massive discoveries, 


and upon them his fame must mainly rest. But 
even without them, sufficient would remain to secure 
for him a high and lasting scientific reputation. 
We should still have his researches on the Lique- 
faction of Gases; on Frictional Electricity; on the 
Electricity of the Grymnotus ; on the source of Power 
in the Hydro-electric machine, the two last investi- 
gations being untouched in the foregoing memoir; 
on Electro-magnetic Rotations ; on Regelation ; all 
his more purely Chemical Researches, including his 
discovery of Benzol. Besides these he published a 
multitude of minor papers, most of which, in some 
way or other, illustrate his genius. I have made 
no allusion to his power and sweetness as a lecturer. 
Taking him for all and all, I think it will be con- 
ceded that Michael Faraday was the greatest experi- 
mental philosopher the world has ever seen ; and I 
will add the opinion, that the progress of future 
research will tend, not to dim or to diminish, but to 
enhance and glorify the labours of this mighty in- 


Thus far I have confined myself to topics mainly 
interesting to the man of science, endeavouring, 
however, to treat them in a manner unrepellent to 
the general reader who might wish to obtain a notion 

L 2 


of Faraday as a worker. On others will fall the 
duty of presenting to the world a picture of the man. 
But I know you will permit me to add to the 
foregoing analysis a few personal reminiscences and 
remarks, tending to connect Faraday with a wider 
world than that of science namely, with the general 
human heart. 

One word in reference to his married life, in 
addition to what has been already said, may find a 
place here. As in the former case, Faraday shall be 
his own spokesman. The following paragraph, 
though written in the third person, is from his 
hand : ' On June 12, 1841, he married, an event 
which more than any other contributed to his 
earthly happiness and healthful state of mind. The 
union has continued for twenty- eight years and has 
in no wise changed, except in the depth and strength 
of its character.' 

Faraday's immediate forefathers lived in a little 
place called Clapham Wood Hall, in Yorkshire. 
Here dwelt Robert Faraday and Elizabeth his wife, 
who had ten children, one of them, James Faraday, 
born in 1761, being father to the philosopher. A 
family tradition exists that the Faradays came origi- 
nally from Ireland. Faraday himself has more than 
once expressed to me his belief that his blood was in 
part Celtic, but how much of it was so, or when the 


infusion took place, he was unable to say. He could 
imitate the Irish brogue, and his wonderful vivacity 
may have been in part due to his extraction. But 
there were other qualities which we should hardly 
think of deriving from Ireland. The most prominent 
of these was his sense of order, which ran like a 
luminous beam through all the transactions of his 
life. The most entangled and complicated matters 
fell into harmony in his hands. His mode of keeping 
accounts excited the admiration of the managing 
board of this Institution. And his science was simi- 
larly ordered. In his Experimental Researches, he 
numbered every paragraph, and welded their various 
parts together by incessant reference. His private 
notes of the Experimental Researches, which are 
happily preserved, are similarly numbered : their last 
paragraph bears the figure 16,041. His working 
qualities, moreover, showed the tenacity of the Teu- 
ton. His nature was impulsive, but there was a force 
behind the impulse which did not permit it to retreat. 
If in his warm moments he formed a resolution, in 
his cool ones he made that resolution good. Thus 
his fire was that of a solid combustible, not that of a 
gas, which blazes suddenly, and dies as suddenly 

And here I must claim your tolerance for the limits 
by which I am confined. No materials for a life of 


Faraday are in my hands, and what I have now to 
say has arisen almost wholly out of our close personal 

Letters of his, covering a period of sixteen years, 
are before me, each one of which contains some 
characteristic utterance; strong, yet delicate in 
counsel, joyful in encouragement, and warm in affec- 
tion. Eeferences which would be pleasant to such 
of them as still live are made to Humboldt, Biot, 
Dumas, Chevreul, Magnus, and Arago. Accident 
brought these names prominently forward; but many 
others would be required to complete his list of con- 
tinental friends. He prized the love and sympathy 
of men prized it almost more than the renown 
which his science brought him. Nearly a dozen 
years ago it fell to my lot to write a review of his 
' Experimental Researches ' for the ' Philosophical 
Magazine.' After he had read it, he took me by the 
hand, and said, ' Tyndall, the sweetest reward of my 
work is the sympathy and good will which it has 
caused to flow in upon me from all quarters of the 
world.' Among his letters I find little sparks of 
kindness, precious to no one but myself, but more 
precious to me than all. He would peep into the 
laboratory when he thought me weary, and take me 
upstairs with him to rest. And if I happened to be 
absent he would leave a little note for me, couched 


in this or some other similar form : ' Dear Tyndall 
I was looking for you, because we were at tea we 
have not yet done will you come up ? ' I frequently 
shared his early dinner ; almost always, in fact, while 
my lectures were going on. There was no trace of 
asceticism in his nature. He preferred the meat and 
wine of life to its locusts and wild honey. Never 
once during an intimacy of fifteen years did he men- 
tion religion to me, save when I drew him on to the 
subject. He then spoke to me without hesitation or 
reluctance ; not with any apparent desire to ' improve 
the occasion,' but to give me such information as I 
sought. He believed the human heart to be swayed 
by a power to which science or logic opened no 
approach, and right or wrong, this faith, held in per- 
fect tolerance of the faiths of others, strengthened 
and beautified his life. 

From the letters just referred to, I will select three 
for publication here. I choose the first, because it 
contains a passage revealing the feelings with which 
Faraday regarded his vocation, and also because 
it contains an allusion which will give pleasure to a 

'Ventnor, Isle of Wight, June 28, 1854. 

' MY DEAR TYNDALL, You see by the top of this 
letter how much habit prevails over me ; I have just 


read yours from thence, and yet I think my self there. 
However, I have left its science in very good keeping, 
and I am glad to learn that you are at experiment 
once more. But how is the health ? Not well, I fear. 
I wish you would get yourself strong first and work 
afterwards. As for the fruits, I am sure they will be 
good, for though I sometimes despond as regards 
myself, I do not as regards you. You are young, 
I am old. . . . But then our subjects are so glorious, 
that to work at them rejoices and encourages the feeblest; 
delights and enchants the strongest. 

6 1 have not yet seen anything from Magnus. 
Thoughts of him always delight me. We shall look 
at his black sulphur together. I heard from Schon- 
bein the other day. He tells me that Liebig is full 
of ozone, i>e. of allotropic oxygen. 

' Good-bye for the present. 

f Ever, my dear Tyndall, 
6 Yours truly, 

The contemplation of Nature, and his own rela- 
tion to her, produced in Faraday a kind of spiritual 
exaltation which makes itself manifest here. His 
religious feeling and his philosophy could not be kept 
apart ; there was an habitual overflow of the one into 
the other. 


Whether he or another was its exponent, he ap- 
peared to take equal delight in science. A good 
experiment would make him almost dance with 
delight. In November, 1850, he wrote to me thus : 
c I hope some day to take up the point respecting the 
magnetism of associated particles. In the mean 
time I rejoice at every addition to the facts and 
reasoning connected with the subject. When science 
is a republic, then it gains : and though I am no 
republican in other matters, I am in that.' All his 
letters illustrate this catholicity of feeling. Ten years 
ago, when going down to Brighton, he carried with 
him a little paper I had just completed, and after- 
wards wrote to me. His letter is a mere sample of 
the sympathy which he always showed to me and my 

Brighton, December 9, 1857. 

c MY DEAR TYNDALL, I cannot resist the pleasure 
of saying how very much I have enjoyed your paper. 
Every part has given me delight. It goes on from 
point to point beautifully. You will find many pencil 
marks, for I made them as I read. I let them stand, 
for though many of them receive their answer as 
the story proceeds, yet they show how the wording 
impresses a mind fresh to the subject, and perhaps 
here and there you may like to alter it slightly, if 
you wish the full idea, i.e. not an inaccurate one, to 


be suggested at first ; and yet after all I believe it is 
not your exposition, but the natural jumping to a 
conclusion that affects or has affected my pencil. 

6 We return on Friday, when I will return you the 

6 Ever truly yours, 


The third letter will come in its proper place to- 
wards the end. 

While once conversing with Faraday on science, in 
its relations to commerce and litigation, he said to 
me, that at a certain period of his career, he was 
forced definitely to ask himself, and finally to decide 
whether he should make wealth or science the pursuit 
of his life. He could not serve both masters, and he 
was therefore compelled to choose between them. 
After the discovery of magneto-electricity his fame 
was so noised abroad, that the commercial world 
would hardly have considered any remuneration too 
high for the aid of abilities like his. Even before he 
became so famous, he had done a little ' professional 
business.' This was the phrase he applied to his 
purely commercial work. His friend, Eichard 
Phillips, for example, had induced him to undertake 
a number of analyses, which produced, in the year 
1830, an addition to his income of more than a 


thousand pounds ; and in 1831, a still greater addi- 
tion. He had only to will it to raise in 1832 his 
professional business income to 5,OOOZ. a year. In- 
deed, this is a wholly insufficient estimate of what he 
might, with ease, have realised annually during the 
last thirty years of his life. 

While restudying the Experimental Eesearches 
with reference to the present memoir, the conver- 
sation with Faraday here alluded to canie to my 
recollection, and I sought to ascertain the period 
when the question, ' wealth or science,' had presented 
itself with such emphasis to his mind. I fixed upon 
the year 1831 or 1832, for it seemed beyond the 
range of human power to pursue science as he had 
done during the subsequent years, and to pursue 
commercial work at the same time. To test this 
conclusion I asked permission to see his accounts, 
and on my own responsibility, I will state the result. 
In 1832, his professional business-income, instead of 
rising to 5,0001, or more, fell from 1,090?. 4s. to 155Z. 
9s. From this it fell with slight oscillations to 92Z. in 
1837, and to zero in 1838. Between 1839 and 1845, it 
never, except in one instance, exceeded 221. ; being 
for the most part much under this. The exceptional 
year referred to was that in which he and Sir Charles 
Lyell were engaged by Government to write a report 
on the Haswell Colliery explosion, and then his 


business income rose to 1121. From the end of 1845 
to the day of his death, Faraday's annual professional 
business income was exactly zero. Taking the dura- 
tion of his life into account, this son of a blacksmith, 
and apprentice to a bookbinder, had to decide 
between a fortune of 150,000?. on the one side, and 
his undowered science on the other. He chose the 
latter, and died a poor man. But his was the glory 
of holding aloft among the nations the scientific 
name of England for a period of forty years. 

The outward and visible signs of fame were also 
of less account to him than to most men. He had 
been loaded with scientific honours from all parts of 
the world. Without, I imagine, a dissentient voice, 
he was regarded as the prince of the physical in- 
vestigators of the present age. The highest scien- 
tific position in this country he had, however, never 
filled. When the late excellent and lamented Lord 
Wrottesley resigned the presidency of the Royal 
Society, a deputation from the council, consisting of 
his Lordship, Mr. Grove, and Mr. Gassiot, waited 
upon Faraday, to urge him to accept the president's 
chair. All that argument or friendly persuasion 
could do was done to induce him to yield to the 
wishes of the council, which was also the unanimous 
wish of scientific men. A knowledge of the quick- 
ness of his own nature had induced in Faraday the 


liabit of requiring an interval of reflection, before lie 
decided upon any question of importance. In the 
present instance he followed his usual habit, and 
begged for a little time. 

On the following morning, I went up to his 
room, and said on entering that I had come to 
him with some anxiety of mind. He demanded 
its cause, and I responded 'lest you should have 
decided against the wishes of the deputation that 
waited on you yesterday.' ' You would not urge 
me to undertake this responsibility/ he said. ' I 
not only urge you,' was my reply, c but I consider it 
your bounden duty to accept it.' He spoke of the 
labour that it would involve ; urged that it was not 
in his nature to take things easy; and that if he 
became president, he would surely have to stir many 
new questions, and agitate for some changes. I 
said that in such cases he would find himself sup- 
ported by the youth and strength of the Eoyal 
Society. This, however, did not seem to satisfy him. 
Mrs. Faraday came into the room, and he appealed 
to her. Her decision was adverse, and I deprecated 
her decision. ( Tyndall,' he said at length, ' I must 
remain plain Michael Faraday to the last; and let 
me now tell you, that if I accepted the honour which 
the Royal Society desires to confer upon me, I would 
not answer for the integrity of my intellect for a 


single year.' I urged him no more, and Lord 
Wrottesley had a most worthy successor in Sir Ben- 
jamin Brodie. 

After the death of the Duke of Northumberland, 
our Board of Managers wished to see Mr. Faraday 
finish his career as President of the Institution, 
which he had entered on weekly wages more than 
half a century before. But he would have nothing 
to do with the presidency. He wished for rest, and 
the reverent affection of his friends was to him in- 
finitely more precious than all the honours of official 

The first requisite of the intellectual life of Fara- 
day was the independence of his mind ; and though 
prompt to urge obedience where obedience was due, 
with every right assertion of manhood he intensely 
sympathized. Even rashness on the side of honour 
found from him ready forgiveness, if not open 
applause. The wisdom of years, tempered by a 
character of this kind, rendered his counsel pecu- 
liarly precious to men sensitive like himself. I often 
sought that counsel, and, with your permission, will 
illustrate its character by one or two typical in- 

In 1855, I was appointed examiner under the 
Council for Military Education. At that time, as 
indeed now, I entertained strong convictions as to 


the enormous utility of physical science to officers of 
artillery and engineers, and whenever opportunity 
offered, I expressed this conviction without reserve. 
I did not think the recognition, though considerable, 
accorded to physical science in those examinations 
at all proportionate to its importance ; and this pro- 
bably rendered me more jealous than I otherwise 
should have been of its claims. 

In Trinity College, Dublin, a school had been 
organized with reference to the Woolwich examina- 
tions, and a large number of exceedingly well-in- 
structed young gentlemen were sent over from Dublin, 
to compete for appointments in the artillery and 
engineers. The result of one examination was par- 
ticularly satisfactory to me; indeed the marks ob- 
tained appeared so eloquent, that I forbore saying 
a word about them. My colleagues, however, followed 
the Usual custom of sending in brief reports with 
their returns of marks. After the results were pub- 
lished, a leading article appeared in 6 The Times,' in 
which the reports were largely quoted, praise being 
bestowed on all the candidates, except the excellent 
young fellows who had passed through my hands. 

A letter from Trinity College drew my attention 
to this article, bitterly complaining, that whereas the 
marks proved them to be the best of all, the science 
candidates were wholly ignored. I tried to set 


matters right by publishing, on my own responsi- 
bility, a letter in ' The Times.' The act I knew 
could not bear justification from the War-Office point 
of view ; and I expected and risked the displeasure 
of my superiors. The merited reprimand promptly 
came. c Highly as the Secretary of State for War 
might value the expression of Professor TyndalPs 
opinion, he begged to say that an examiner, appointed 
by His Royal Highness the Commander-in-Chief, had 
no right to appear in the public papers as Professor 
Tyndall has done, without the sanction of the War 
Office.' Nothing could be more just than this re- 
proof, but I did not like to rest under it. I wrote a re- 
ply, and previous to sending it took it up to Faraday. 
We sat together before his fire, and he looked very 
earnest as he rubbed his hands and pondered. The 
following conversation then passed between us : 

F. You certainly have received a reprimand, 
Tyndall ; but the matter is over, and if you wish to 
accept the reproof, you will hear no more about it. 

T. But I do not wish to accept it. 

F. Then you know what the consequence of send- 
ing that letter will be ? 

T. I do. 

F. They will dismiss you. 

T. I know it. 

F. Then send the letter ! 


The letter was firm, but respectful; it acknow- 
ledged the justice of the censure, but expressed 
neither repentance nor regret. Faraday, in his gra- 
cious way, slightly altered a sentence or two to make 
it more respectful still. It was duly sent, and on 
the following day I entered the Institution with the 
conviction that my dismissal was there before me. 
Weeks, however, passed. At length the well-known, 
envelope appeared, and I broke the seal, not doubt- 
ing the contents. They were very different from 
what I expected. e The Secretary of State for War 
has received Professor TyndalTs letter, and deems the 
explanation therein given perfectly satisfactory.' I have 
often wished for an opportunity of publicly acknow- 
ledging this liberal treatment, proving, as it did, 
that Lord Panmure could discern and make allow- 
ance for a good intention, though it involved an 
offence against routine. For many years subse- 
quently it was my privilege to act under that ex- 
cellent body, the Council for Military Education. 

On another occasion of this kind, having en- 
couraged me in a somewhat hardy resolution I had 
formed, Faraday backed his encouragement by an 
illustration drawn from his own life. The subject 
will interest you, and it is so sure to be talked 
about in the world, that no avoidable harm can arise 
from its introduction here. 


In the year 1835, Sir Eobert Peel wished to offer 
Faraday a pension, but that great statesman quitted 
office before he was able to realise his wish. The 
Minister who founded these pensions intended them, 
I believe, to be marks of honour which even proud 
men might accept without compromise of indepen- 
dence. When, however, the intimation first reached 
Faraday, in an unofficial way, he wrote a letter 
announcing his determination to decline the pension ; 
and stating that he was quite competent to earn his 
livelihood himself. That letter still exists, but it was 
never sent, Faraday's repugnance having been over- 
ruled by his friends. When Lord Melbourne came 
into office, he desired to see Faraday ; and probably 
in utter ignorance of the man for, unhappily for 
them and us, Ministers of State in England are only 
too often ignorant of great Englishmen his Lord- 
ship said something that must have deeply displeased 
his visitor. The whole circumstances were once 
communicated to me, but I have forgotten the de- 
tails. The term ' humbug,' I think, was incau- 
tiously employed by his Lordship, and other ex- 
pressions were used of a similar kind. Faraday 
quitted the Minister with his own resolves, and that 
evening he left his card and a short and decisive note 
at the residence of Lord Melbourne, stating that he 
had manifestly mistaken his Lordship's intention of 


honouring science in his person, and declining to 
have anything whatever to do with the proposed 
pension. The good-humoured nobleman at first con- 
sidered the matter a capital joke ; but he was after- 
wards led to look at it more seriously. An excellent 
lady, who was a friend both to Faraday and the 
Minister, tried to arrange matters between them ; but 
she found Faraday very difficult to move from the 
position he had assumed. After many fruitless efforts, 
she at length begged of him to state what he would 
require of Lord Melbourne to induce him to change 
his mind. He replied, C I should require from his 
Lordship what I have no right or reason to expect 
that he would grant a written apology for the 
words he permitted himself to use to me.' The 
required apology came, frank and full, creditable, I 
thought, alike to the Prime Minister and the Phi- 

Considering the enormous strain imposed on Fara- 
day's intellect, the boy-like buoyancy even of his 
later years was astonishing. He was often prostrate, 
but he had immense resiliency, which he brought 
into action by getting away from London whenever 
his health failed. I have already indicated the 
thoughts which filled his mind during the evening of 
his life. He brooded on magnetic media and lines of 
force ; and the great object of the last investigation 


lie ever undertook was the decision of the ques- 
tion whether magnetic force requires time for its 
propagation. How he proposed to attack this sub- 
ject we may never know. But he has left some 
beautiful apparatus behind; delicate wheels and 
pinions, and associated mirrors, which were to have 
been employed in the investigation. The mere con- 
ception of such an inquiry is an illustration of his 
strength and hopefulness, and it is impossible to say 
to what results it might have led him. But the 
work was too heavy for his tired brain. It was long 
before he could bring himself to relinquish it, and 
during this struggle he often suffered from fatigue of 
mind. It was at this period, and before he resigned 
himself to the repose which marked the last two 
years of his life, that he wrote to me the following 
letter one of many priceless letters now before me 
which reveals, more than anything another pen 
could express, the state of his mind at the time. I 
was sometimes censured in his presence for my 
doings in the Alps, but his constant reply was, ' Let 
him alone, he knows how to take care of himself.' 
In this letter, anxiety on this score reveals itself, for 
the first time. 


'Hampton Court, August 1, 1861. 

DEAR TYNDALL, I do not know whether 
my letter will catch yon, bnt I will risk it, thongh 
feeling very unfit to communicate with a man whose 
life is as vivid and active as yonrs ; bnt the receipt 
of yonr kind letter makes me to know that thongh I 
forget, I am not forgotten, and thongh I am not able 
to remember at the end of a line what was said at 
the beginning of it, the imperfect marks will convey 
to yon some sense of what I long to say. We had 
heard of yonr illness through Miss Moore, and I was 
therefore very glad to learn that yon are now quite 
well ; do not run too many risks, or make your hap- 
piness depend too much upon dangers, or the hunt- 
ing of them. Sometimes the very thinking of you, 
and what you may be about, wearies me with fears, 
and then the cogitations pause and change, but 
without giving me rest. I know that much of this 
depends upon my own worn-out nature, and I do not 
know why I write it, save that when I write to you 
1 cannot help thinking it, and the thoughts stand 
in the way of other matter. 

* See what a strange desultory epistle I am writing 


to you, and yet I feel so weary that I long to leave 
my desk and go to the couch. 

' My dear wife and Jane desire their kindest re- 
membrances : I hear them in the next room : . . . . 
I forget but not you, my dear Tyndall, for I am 
' Ever yours, 


This weariness subsided when he relinquished his 
work, and I have a cheerful letter from him, written 
in the autumn of 1865. But towards the close of 
that year he had an attack of illness, from which he 
never completely rallied. He continued to attend 
the Friday Evening Meetings, but the advance of 
infirmity was apparent to us all. Complete rest 
became finally essential to him, and he ceased to ap- 
pear among us. There was no pain in his decline to 
trouble the memory of those who loved him. Slowly 
and peacefully he sank towards his final rest, and 
when it came, his death was a falling asleep. In 
the fulness of his honours and of his age he quitted 
us ; the good fight fought, the work of duty shall I 
not say of glory done. The 6 Jane ' referred to in 
the foregoing letter is Faraday's niece, Miss Jane 
Barnard, who with an affection raised almost to 
religious devotion, watched him and tended him to 
the end. 


I saw Mr. Faraday for the first time on my return 
from Marburg in 1850. I came to the Royal Insti- 
tution, and sent up my card, with a copy of the paper 
which Knoblauch and myself had just completed. 
He came down and conversed with me for half-an- 
hour. I could not fail to remark the wonderful play 
of intellect and kindly feeling exhibited by his coun- 
tenance. When he was in good health the question 
of his age would never occur to you. In the light 
and laughter of his eyes you never thought of his 
grey hairs. He was then on the point of publishing 
one of his papers on Magne-crystallic action, and he 
had time to refer in a nattering note to the memoir 
I placed in his hands. I returned to Germany, 
worked there for nearly another year, and in June 
1851 came back finally from Berlin to England. 
Then, for the first time, and on my way to the meet- 
ing of the British Association, at Ipswich, I met a 
man who has since made his mark upon the intel- 
lect of his time ; who has long been, and who by the 
strong law of natural affinity must continue to be, a 
brother to me. We were both without definite out- 
look at the time, needing proper work, and only 
anxious to have it* to perform. The chairs of Na- 
tural History and of Physics being advertised as 
vacant in the University of Toronto, we applied for 
them, he for the one, I for the other ; but, possibly 


guided by a prophetic instinct, the University au- 
thorities declined having anything to do with either 
of us. If I remember aright, we were equally un- 
lucky elsewhere. 

One of Faraday's earliest letters to me had refer- 
ence to this Toronto business, which he thought it 
unwise in me to neglect. But Toronto had its own 
notions, and in 1853, at the instance of Dr. Bence 
Jones, and on the recommendation of Faraday him- 
self, a chair of physics at the Royal Institution was 
offered to me. I was tempted at the same time to 
go elsewhere, but a strong attraction drew me to his 
side. Let me say that it was mainly his and other 
friendships, precious to me beyond all expression, 
that caused me to value my position here more 
highly than any other that could be offered to me in 
this land. Nor is it for its honour, though surely 
that is great, but for the strong personal ties that 
bind me to it, that I now chiefly prize this place. 
You might not credit me were I to tell you how 
lightly I value the honour of being Faraday's succes- 
sor compared with the honour of having been Fara- 
day's friend. His friendship was energy and in- 
spiration ; his ' mantle ' is a burden almost too heavy 
to be borne. 

Sometimes during the last year of his life, by the 


permission or invitation of Mrs. Faraday, I went 
up to his rooms to see him. The deep radiance, 
which in his time of strength flashed with such ex- 
traordinary power from his countenance, had sub- 
sided to a calm and kindly light, by which my latest 
memory of him is warmed and illuminated. I knelt 
one day beside him on the carpet an-d placed my 
hand upon his knee; he stroked it affectionately, 
smiled, and murmured, in a low soft voice, the last 
words that I remember as having been spoken to me 
by Michael Faraday. 

It was my wish and aspiration to play the part of 
Schiller to this Goethe ; and he was at times so 
strong and joyful his body so active, and his intel- 
lect so clear as to suggest to me the thought that 
he, like Goethe, would see the younger man laid low. 
Destiny ruled otherwise, and now he is but a 
memory to us all. Surely no memory could be more 
beautiful. He was equally rich in mind and heart. 
The fairest traits of a character sketched by Paul, 
found in him perfect illustration. For he was 
6 blameless, vigilant, sober, of good behaviour, apt to 
teach, not given to filthy lucre.' He had not a 
trace of worldly ambition ; he declared his duty 
to his Sovereign by going to the levee once a 
year, but beyond this he never sought contact with 


the great. The life of his spirit and of his intel- 
lect was so full, that the things which rnen most 
strive after were absolutely indifferent to him. 
'Give me health and a day,' says the brave Emer- 
son, 'and I will make the pomp of emperors 
' ridiculous.' In an eminent degree Faraday could 
say the same. What to him was the splendour 
of a palace compared with a thunderstorm upon 
Brighton Downs? what among all the appli- 
ances of royalty to compare with the setting sun? 
I refer to a thunderstorm and a sunset, because 
these things excited a kind of ecstasy in his mind, 
and to a mind open to such ecstasy the pomps and 
pleasures of the world are usually of small ac- 
count. Nature, not education, rendered Faraday 
strong and refined. A favourite experiment of his 
own was representative of himself. He loved to show 
that water in crystallizing excluded all foreign ingre- 
dients, however intimately they might be mixed with 
it. Out of acids, alkalis, or saline solutions, the 
crystal came sweet and pure. By some such natural 
process in the formation of this man, beauty and 
nobleness coalesced, to the exclusion of everything 
vulgar and low. He did not learn his gentleness in 
the world, for he withdrew himself from its culture; 
and still this land of England contained no truer 


gentleman than he. Not half his greatness was in- 
corporate in his science, for science could not reveal 
the bravery and delicacy of his heart. 

But it is time that I should end these weak words, 
and lay my poor garland on the grave of this 

Just and faithful knight of God. 






I. The Vegetable Kingdom. II, Recent Shells. III. Worms, Crustacea, Spiders, 
Scorpions, etc. IV. Insects. V. Fishes. VI. Reptiles. VII. Birds. (VIII. 
Mammalia, just ready). IX. Characteristic British Fossils, stratigraphically 

London : Society for Promoting Christian Knowledge. 

I. Chart of Fossil Crustacea (with descriptive Catalogue.) II. Chart of Characterises 
British Tertiary Fossils, stratigraphically arranged. 



fT^HERE are few men who have done more to promote a taste for 
JL Natural History especially among young people than Mr. J. W. 
Lowry. His Natural History Charts, though designed and engraved 
by himself, have all been carried out under the direction of able 
naturalists, in the several branches of which they treat, among these may 
be named such men as the late Mr. Henfrey and Dr. S. P. Woodward, 
Mr. Adam White, Dr. Baird, Mr. Gosse, and Mr. George Gray. 

Visual education is not only the first form of training by which the 
attention of youth is attracted, but it is also that which remains longest 
impressed upon our mental retina. These charts are calculated, how- 
ever, to afford education of a still higher character, and to pupils of all 
ages ; they are admirably fitted for the school and class-room, and every 
teacher of Natural History should possess a copy of each, nor can a museum 
be complete without these admirable and instructive guide-maps. 

The Chart of Fossil Crustacea by Messrs. J. W. Salter and H. Wood- 
ward, gives a conspectus of a single class, arranged not only in strati- 
graphical series, but in zoological order. It contains nearly 500 figures, 
and is, moreover, accompanied by a short descriptive catalogue. 4> 

That of Characteristic British Tertiary Fossils is an elaborate view of 
the topmost or newest section of the Chart of British Fossils, and holds 
the same relation to it which a map of Europe does to a map of the 
World. It contains upwards of 800 figures of characteristic shells and 
other organisms found in the series of formations of Cainozoic or Tertiary 
age, which have been engraved by Mr. Lowry expressly for this work, 
and selected by him with great care, assisted by Messrs. Kobt. Etheridge. 
Searles V. Wood, Fred. E. Edwards, and other geologists of eminence, 
and contains a mass of information never before collected in so compact 
a form for reference. Every specimen is not only named, but has its 
natural size indicated against it, if it be enlarged or reduced. Those 
Crag species which occur in more than one bed are also marked by the 
initial letter of the beds in which they have been found, thus giving 
the range of each. 

We strongly recommend these charts to all lovers of Natural History, 
but would especially call the attention of geologists to this new and 
GEOLOGICAL MAGAZINE, No. 28. Oct., 1866, p. 464. 

* For a full description of this Chart of Fossil Crustacea, see British Association Reports, 
Sections C. and D. Birmingham, 1865 ; and GEOLOGICAL MAGAZINE, Vol. II., p. 468. 








This Chart contains figures of organic remains, from the PLEISTOCENE 
(Land, Fresh- water, and Marine) ; the CRAG, and EOCENE formations, 
the latter divided into upper, middle, and lower, according to the divi- 
sions adopted by the Geological Survey of Great Britain. 
PRICE: Mounted on linen to fold in Case, or mounted on Boilers and 
Varnished, 10s. ; mounted to fold in thin cover, 7s. Qd. 





Accompanied by a descriptive Catalogue giving Localities, &c. f &c. 



Besides being Stratigraphically Arranged, as shown by horizontal lines 

marking the different Formations, this Chart is intended to show at a 

glance the development in Geological time of the different orders of the 

class Crustacea, by curved and nearly vertical lines, which separate the 

various orders, and show in what formations they first came into existence 

(as far as our knowledge yet extends), and where they ceased to live. 

PRICE : Mounted to fold in Case with Descriptive Catalogue, 10s. Qd. 

Mounted on Rollers Varnished, with Descriptive Catalogue, 13s. 


Published by J, TENNANT, Mineralogist to the dueen, 149, Strand, W.C. 




This book is due on the last date stamped below, or 

on the date to which renewed. 
Renewed books are subject to immediate recall. 



NO!/ 2 5 '66 -5PM 


LD 2lA-40m-4,'63 

General Library 

University of California