F. (François) Arago.

Biographies of distinguished scientific men (Volume 2) online

. (page 13 of 38)
Online LibraryF. (François) AragoBiographies of distinguished scientific men (Volume 2) → online text (page 13 of 38)
Font size
QR-code for this ebook

to reconcile it with mechanical notions; and this more precisely as
to the notion of transverse vibrations alone being produced, which
constituted this theory in all its simplicity ; whereas Young had (as
we have just seen) believed both these and longitudinal \\hrat\ons to
coexist. To establish this point, he expressly says, was the main dif-
ficulty which embarrassed him.i — Translator.

* The essential principle of the reflective goniometer of Wollaston
is extremely simple, and consists in this: a piece of crystal or any

1 Ann. de Chimie, 1831, torn. xvii. p. 184.

162 MALUS.

added to the perfection of the English instrument by-
giving it the principle of repetition.'^ He desired thus to

other object having two plane surfaces a and J, capable of reflecting
light, is fixed at the centre of a graduated circle, to its index i. It is
first brought into such a position that the image of an object x, by re-
flexion from the surface «, is seen by the eye coincident with another
object Y, seen directly; the index marking 0. It is then turned round
till the same thing is observed with the surf^ice &, when the index
marks/;; the arc op measures the inclination of the two surfaces a b,
since the surface h now occupies the same position with respect to the
circle which a did before. — Translator.
* The principle of '■'■ repetition'''' may be thus briefly stated. To any

graduated circular instrument intended for measuring the angular
distance of two objects x y, there is added an inner circle c, moving
about the same centre, to which is fixed the part t, which (by what-
ever means) fixes the position of the object; while an index i can be
either fixed to the inner c, or to the outer circle a, by clamping, or
can move independently. First, the index i being clamped to c, then
pointing to 0, while t is directed to the object x; the part t is then
turned to Y, while i moves over an arc o 1, equal to that between x
and Y, and points to 1. Secondly, i is clamped to a at ], and un-
damped from c; < is moved back on x; i is undamped from a, and
clamped to c; and Amoving with i is directed to y; i consequently
comes to 2, passing over an equal arc. Thirdly, the same operation is
repeated, and i comes to 3, and so on for as many times as may be
desired. The arc read off in each instance will, from the errors of


be able to compensate the errors of division by successive
readings off, and to render tlie observer indejiendent of
the inaccuracies which the artist might have committed
in dividing the circles. Unfortunately natural crystals,
on which it is possible to use with any advantage the
metliod of re[)etition, are by no means common. But
the method preserves all its theoretical value when it is
the object, in optical researches, to measure the angles of
prisms formed by truly worked and perfectly polished
planes. At the same time it is but just to observe that
the idea of employing the reflexion of light for the meas-
urement of angles, is due to the celebrated physicist


The more than ordinary labours of Malus, of which
I have just given a rapid analysis, obtained for him the
most sincere testimonials of esteem and admiration from
men of science of all countries. He was named a mem-
ber of the Society of Arcueil, wdiich was composed of a
small number of men of science assembling under the
auspices of Laplace and Rerthollet.*

A place in the Section of Physics of the Listitute hav-
ing become vacant in 1810 by the death of Montgolfier,
Malus was naturally one of the candidates who presented
themselves to fill up the place of the illustrious physicist.

graduation, be diflerent. As avij number of repetitions may be taken,
we may have a mean result accurate to any extent desired. — Trans-

* The members of the Society of Arcueil were — Laplace, C. L. Ber-
thollet, Biot, Gay-Lussac, Humboldt, Tli^nard, De Candolle, Collet-
Descoutils, A. B. Berthollet, Malus, Arago, Berard, Chaptal, Dulong,


Among the candidates there was conspicuous an en-
gineer of roads and bridges, who had also borne a part in
the Egyptian expedition, and whose connections with the
academicians were numerous and of old date. Every
one, therefore, foresaw that the place would be vigorously
contested. On the day of election, August 13, 1810, one
of Malus's friends undertook to bring him the news of
the result the moment it was known. But by an un-
fortunate combination of circumstances the scrutiny was
not opened till a later time than usual. Malus obtained
31 votes, his opponent 22. The friend of Malus, just
alluded to, did not lose a moment in going to him to an-
nounce the happy result. But the usual hour at which
the news ought to have reached him having long passed,
the great physicist believed himself to have been defeated,
and abandoned himself, in spite of all the consolations
which his wife afforded him, to the deepest despondency.
Thus the inti-epid soldier of the army of Sambre and
Meuse, — he who had seen the near approach of death at
the combat of Chebreys, at the battle of the Pyramids,
on the day of the revolt of Cairo, in the immortal day of
Heliopolis, — the oificer who at Jaffa and Damietta had
sustained the attacks of the plague with such firmness of
mind, — allowed himself to yield and sink under the sup-
posed want of success in an election of the Academy !
Let us preserve and value these recollections ! Who
will venture to maintain the uselessness of such institu-
tions when he sees the author of one of the greatest dis-
coveries of modern times attach such a price to the title
of Academician ? Who does not perceive with what
emulation young experimentalists ought to be animated,
when the society in which they aspire to take their place,
constantly anxious to repel from itself all suspicion of


party influence, holds itself in the first position in public
esteem by taking the greatest care always to recruit its
ranks solely from among those who are most worthy.

Mains had become major, a rank corresponding with
that of lieutenant-colonel, December 5, 1810. The gov-
ernment had often entrusted him with the mission to
classify in their order of merit the officers of artillery and
engineers at their departure from the Practical School of
Metz. He became afterwards examiner of the pupils of
the Ecole Polytechnique for descriptive geometry, and
the sciences dependent on it.

On the 14tli Vendemiaire an IX.* Mains wrote from
Benisouf to his friend Lancret : "• I live here like a her-
mit ; I pass whole days without speaking a word." It
appeared that our friend often abandoned himself to his
taste for silence. The pupils of the Ecole Polytechnique
and the Ecole d'Application, related that in going over
their exerqises he contented himself by pointing out with
his finger the parts on which he required explanations,
without saying a word. This mode of asking, which con-
trasted so singularly with that of some other examiners, his
contemporaries, not a little astonished them. But they
did not the less do complete justice to the enlightened
patience, the intelligence, and the perfect honesty which
characterized all the decisions made by Malus at the close
of his examinations. Malus filled, ad interim, in 1811,
the functions of Director of Studies at the Ecole Poly-
technique. There were only wanting some regimental
formalities to entrust to him definitively this important

The companion of his choice whom he went to seek at
Giessen after the expedition to Egypt, threw over his
* October 5, 1800.

166 MALUS.

existence an unspeakable happiness. Tlie most cele-
brated academies of Europe were envious to secure him
as an associate. He was loved, honoured, and esteemed
by all who knew him. He might look forward to fresh
and brilliant discoveries of which his genius gave prom-
ise. He possessed, in a word, after the warlike labours
of his youth, all that could attach him to life. It was at
this juncture that, to the loss of his connections, of his
friends, of the sciences, and the national glory, life failed

A consumption, of Avhich he felt the first symptoms
about the middle of 1811, made rapid and alarming
progress, perhaps from some seeds of the plague which
still lurked in his debilitated constitution.

Our colleague did not believe himself fatally attacked ;
for on the evening before his death, he exacted from one
of his friends a promise to accompany him in the course
of the week to Montmorency, whither he wished to retire
for a short time to breathe the country air. But I can
cite a still more demonstrative proof, if possible, of the
illusion under which he laboured till the last. Returned
from Egypt with the full persuasion that consumption is
contagious, and above all that it follows attacks of the
plague, he nevertheless allowed Madame Malus, with his
head reposing against hers, to watch his least motions, and
constantly to be surrounded with the atmosphere which
he had breathed.

To the last this admirable woman could not believe in
the misfortune which threatened her ; and when the
illustrious savant breathed his last, it was needful almost
to use violence to detach her from the inanimate body of
her husband. She survived him only a few months.
Malus was only thirty-seven years of age when the
Academy lost him.




Our colleague was of a middle height and size. In
spite of his reserved and cold manners, he had a friendly
heart. An excellent son, a tender and irreproachable
husband, a devoted friend, — he has left behind him, in
the minds of all who knew him, the reputation, so much
to be envied, of a truly good man. His conduct, always
beyond reproach even in the most difficult conjunctures,
was not merely dictated by an instinctive sense of right.
In the leisure of his bivouacs in Egypt he had put down
on scattered papers the thoughts and maxims on which
he considered that his conduct ought to be modelled. I
will here cite some of them which would not disgrace, I
think, the most celebrated collections published by any
of our philosophers.

" All the actions of life ought to tend towards the per-
fection of the soul and to social harmony."

" Hope is a source of happiness which is not to be

" I will found my enjoyments on the affections of the
heart, the visions of the imagination, and the spectacle of

" We must exercise patience, as the virtue most abso-
lutely necessary for happiness in our moral existence."

" Mediocrity is a desirable condition of life, since it
requires little expense."

" A great part of life often depends on circumstances.
There are good things of which we must take advantage
as they may occur ; — as we enjoy the spring of the year ;
the brightness of a fine day ; or the odour of a rose."

168 MALUS.

" As we cannot give children the idea of good, we
ought to give them the habit of it."

" Even when we stifle reason, conscience comes as a
corps de reserve to oppose a barrier to irregularity."

" I do not like men who weigh their own good deeds."

I find also in the papers from which the preceding
forms a very short extract, a thought expressed in the
following terms : —

" One becomes the slave of any man, if injustice on his
part can offend and grieve us."

This last precept is full of wisdom ; but did the author
himself always strictly conform to it ? On questions of
scientific pi'iority has he not sometimes, to use his own
expression, become the slave of his opponents? See and
judge for yourselves.

Malus suspected a member of the Institute of Egypt
of having wished to invade his rights on the occasion of
an analytical calculation being communicated to that
learned body. He was so preoccupied with this idea
that in a letter addressed to his colleague he omitted to
write before his signature, " I am, with consideration,
your humble servant." The meaning of this suppres-
sion of a customary form of politeness is indicated in
positive terms in a letter which I have before me from
the oflieer of engineers to his friend Lancret.

A great geometer conceived the idea of a means of
reconciling the phenomena of double refraction with the
principle of " least action," and published on this subject
a note which every one may read in our scientific jour-

Malus was convinced that he had himself first con-
ceived the possibility of this investigation, and that he
had spoken of it publicly before the publication of that


note. He did not content himself with giving publicity
to his first ideas without making any mention of the note
from the pen of so justly celebrated a writer ; but, in
spite of his accustomed reserve, he expressed himself on
this subject on every occasion with a vehemence of which
he would not have been supposed capable.

I will cite a third example : An academician believed
he had a right to contest with Malus the priority in an
important discovery vvitii respect to polarization. Malus
was then at Metz ; his letters bear witness, in terms
which I know not how to repeat, to his extreme irri-
tation. It appeared to him that the pretensions of his
opponent were not well founded in fact, and also that
justice enjoined that he should have been allowed reason-
able time to explore the first beds of a mine the discovery
of which belonged incontestably to him. I ask, never-
theless, whether the susceptibility of Malus can be alto-
gether blamed ? Those who defend with so much reason
the rights of property as the corner-stone of modern
civilization cannot be astonished to see our colleague
attach himself with so much ardour to the defence of
what is the first and most incontestable kind of property,
— that which consists in the works of the intellect. Is it
moreover quite certain, when the illustrious physicist
showed himself so sensitive on the subject of the fruits of
his labours and his genius, that he was not looking for-
ward to one of these solemn meetings where the claims
of men of science to the remembrance of mankind are
enumerated and appreciated before an enlightened and
impartial public, — a judge from whom there is no ap-
peal ? Would it then be strange that, seeing himself in
imagination before this formidable tribunal, he had
dreamed of coming there furnished with the greatest


170 MALUS.

possible number of discoveries uncontested and incon-
testable ? and that under the pressure of these preoccu-
pations he had forgotten for an instant an abstract
maxim of philosophy ? However this may have been,
the integrity and perfect honour of Malus will never be
called in question.

In the collection of thoughts from which I have just
given extracts, I read : —

" There are very few men, who, when they die, leave
behind them any traces of their existence."

I hazard little in asserting that Malus Avill be reck-
oned among these privileged few. His name will go
down to the most distant posterity, coupled with one of
those great discoveries which, independently of their
individual merit, have opened a vast career to the inves-
tigations of science. The immortal name of Malus will
remain ever inseparable from that of polarization, under
which all the most curious, the most fertile, the most bril-
liant phenomena of modern optics are grouped.



The Biography of Fresnel, the first which I had to
read, as Perpetual Secretary, at a public meeting of the
Academy, gave rise to incidents which several historians
of our Revolution of 1830 reported incorrectly. I thus
feel myself bound to give the true version of the facts.
On arriving at the Academy, July the 26th, 1830, I read
in the Moniteur the famous ordinances.* I understood
in an instant all the political consequences which these
acts would bring in their train ; I considered them as a
national misfortune, and I at once resolved to take no
part in the literary solemnity for which we had been con-
voked. I announced my resolution in these lines, which
were to be substituted for the prepared eloge : —

" Gentlemen, — If you have read the Moniteur your
thoughts must doubtless be impressed with a deep sad-
ness, and you will not feel astonished that, for my part,
I have not sufficient calmness of mind to be able to take
part in this ceremony."

I committed the fault of communicating this resolution
to several of my colleagues. From that moment difficul-

* In allusion to the abrogation of the Charter by the ministers of
Charles X.


ties arose on all sides. " If you execute your project,"
they said to me, "the Institute will be abolished; now,
have you, the youngest member of the Academy, any
right to provoke such a catastrophe ? " And to support
this remark, they pointed out to me several savants whose
sole livelihood lay in their appointment as members of
the Institute. These observations, strongly represented,
shook my determination. The strife nevertheless became
hotter ; I could consent to read Fresnel's eloge, but I ob-
stinately refused to cut out the passages which just before
had appeared to be irreproachable, on the necessity to
comply with the charter strictly, if it was not wished
to open again the career of revolutions. Cuvier, from
friendship for me, and also from interest in the Academy,
was especially eager to obtain these suppressions. I
communicated this circumstance to Villemain, who, with-
out perceiving that the great naturalist was within hear-
ing, exclaimed : " That is signal cowardice." From
thence quarrels and personalities arose, of which I should
feel scruples in depositing the remembrance here. The
result, at the time of this lamentable circumstance, Avas,
that the passages in question were preserved in the read-
ing, and became the object, on the part of the public, of
enthusiastic applause, which did not appear to be merited
either by the matter or the form. I must own that I was
much surprised when, on coming out of the meeting, the
Duke of Ragusa whispered to me, " God grant that I
may not have to go to-mori'ow to seek for you at Vin-

introductory remarks. 173

This Biography was read at the Public Meeting of
THE Academy of Sciences on the 26th of July,

Gentlemen, — "There are men who may be succeeded,
but whom no one can replace." These words of one of
the most honoured writers of our time, so often reproduced
as the conventional formula on occasions like the present,
are to-day in my mouth the faithful expression of what I
feel. How could I, indeed, without the deepest emotion,
now occupy before this tribunal a place which has been
so worthily filled, during eight years, by the illustrious
geometer whose unexpected death has been a source of
no less regret to friendship, than to science and to letters.
It is not here. Gentlemen, for the first time that this
sincere avowal of my well-founded diffidence has been
heard. Nearly all the members of the Academy have in
turn been the confidants of my scruples, and their encour-
aging kindness had scarcely succeeded in surmounting
them. Devoted for a long time past to purely scientific
researches, entirely destitute of the literary claims, Avhich
up to this moment had appeared indispensable in the dif-
ficult functions which were confided to me, I could only
possess in the eyes of the Academy the slight merit of
continued zeal, of unlimited devotion to its interests, of
an ardent desire manifested on all occasions to see the
renown which it had acquired enlarge, if that were pos-
sible, and extend itself in all quarters. The void which
M. Fourier has left among us (as I was the first to
acknowledge, and I acknowledged it without reserve) will
be especially felt in these solemn meetings ; it is then
that you will recall to mind that language in which the
most rigorous precision was so happily allied with ele-


gance and with grace. Also I could not but persuade
myself that the indulgence of the Academy presaged in
some degree that with which the public would deign to
honour me ; otherwise could I have dared to make an
inexperienced voice heard here, after the eloquent inter-
preter whom we have just lost, and by the side of him
whom we have the happiness still to possess ?

I hasten, moreover, to explain that this eloge departs
fi'om the ordinary form. I shall even ask the favour of its
being looked upon as simply a scientific memoir, in which,
taking occasion from the labours of our late associate, I
have the opportunity of examining the progress which
has been made in our times in several of the most impor-
tant branches of optics. At an epoch when the courses
of lectures at the College de France, of the Facvlte de
Paris, of the Jardin du Roi are attracting so great a
concourse of auditors, it has occurred to me that the
Academy of Sciences might directly address itself to the
public (that friend of our studies, showing its good will
by so numerous an attendance at our meetings) on some
of the various questions with which we are specially occu-
pied. At the same time this is but a simple attempt of
my own on which I should wish to be enlightened ; the
critic will find me docile. I hope, however, that the satis-
faction of becoming initiated in a few minutes into the
most curious discoveries of one century, may appear a
sufficient compensation for the inevitable tediousness
which so many minute details must cause.

For my own part, the indulgence on which I count
will not prevent my making every effort to render myself
clear. Fontenelle, on a similar occasion, asked of his
auditory (I quote his own expression) " the same atten-
tion which they would necessarily give to the romance of


the Pi'incess of Cleves if they wished closely to follow the
plot, and to know the whole beauty of it." I am aware
that I should not be right in demanding so little ; but, on
the other hand, I have the advantage of speaking before
an assembly familiarized with deep study, and from
which one may confidently claim a degree of attention
which Fontenelle himself, at the commencement of the
eighteenth century, would have found it difficult to gain
from the frivolous assembly he was addressing.




Augustine John Fresnel was born the 10th of May,
1788, at Broglie, near Bernay, in that part of the ancient
province of Normandy which now forms the department
of Eure. His father was an architect, and in this quality
had been entrusted by the military engineer with the
construction of the Fort of Querqueville, at one of the
extremities of the harbour of Cherbourg ; but the revo-
lutionary storm having forced him to abandon this work,
he retired with all his family to a moderate property
which he owned near Caen, at Matthieu, a little village
which already was not without some notoriety, being the
birthplace of the poet John Marot, father of the cele-
brated Clement. Madame Fresnel, whose family name
(Merimee) was also to become one day dear to literature
and the arts, was endowed with the most happy qualities
of heart and mind ; the solid and varied instruction which
she had received in her youth enabled her to assist ac-
tively, during eight consecutive years, in the efforts which


her husband made for the education of their four children.
The progress of the eldest son was brilliant and rapid.
Augustine, on the contrary advanced extremely slowly in
his studies ; at eight years of age he could scarcely read.
This want of success might be attributable to the very
delicate condition of the young scholar, and to the pre-
cautions which it rendered necessary; but it will be still
better understood when it is known that Fresnel never
had any taste for the study of languages ; that he always
set very little value on the exercises which address them-
selves solely to the memory ; that his own, which was
moreover very rebellious generally, refused almost ab-
solutely to retain words from the moment that they
were detached from a clear argument and displaced in
arrangement: I must also own, witliout hesitation, that
those whose predictions concerning the future of a child

Online LibraryF. (François) AragoBiographies of distinguished scientific men (Volume 2) → online text (page 13 of 38)