F. (François) Arago.

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BIOGRAPHIES



OF



DISTINGUISHED SCIENTIFIC MEN,



In Press.
ARAGO'S BIOGRAPHIES

OF

DISTINGUISHED SCIENTIFIC MEN.

SECOND SERIES.

Completing the Work.



BIOGRAPHIES



OF



DISTINGUISHED SCIENTIFIC MEN.



BY FRANCOIS ARAGO,

MEMBER OF THE INSTITUTE.



TRANSLATED BY

ADMIRAL W. H. SMYTH, D.C.L., F.R.S., &c.
THE REV. BADEN POWELL, M.A., F.R.S., &c.

AND

ROBERT GRANT, ESQ., M.A., F.R.A.S.



FIRST SERIES.



BOSTON:
TICKNOR AND FIELDS

M DCCC LIX.








RIVERSIDE, CAMBRIDGE:
PRINTED BY H. 0. HOUGHTON AND COMPAJTT.



^JSS'S^'







.



TRANSLATORS' PREFACE.



THE present volume of the series of English
translations of M. Arago's works consists of his
own autobiography and a selection of some of
his memoirs of eminent scientific men, both con-
tinental and British.

It does not distinctly appear at what period
of his life Arago composed the autobiography,
but it bears throughout the characteristic stamp
of his ardent and energetic disposition. The
reader will, perhaps, hardly suppress a smile at
the indications of self-satisfaction with which
several of the incidents are brought forward,
while the air of romance which invests some
of the adventures may possibly give rise to
some suspicion of occasional embellishment ; on
these points, however, we leave each reader to
judge for himself. In relation to the history of
science, this memoir gives some interesting par-

a*



Vl TRANSLATORS* PREFACE.

ticulars, which disclose to us much of the in-
terior spirit of the Academy of Sciences, not
always of a kind the most creditable to some
of Arago's former contemporaries.

But a far higher interest will be found to
belong to those eloquent memoirs, or eloges of
eminent departed men of science, who had at-
tained the distinction of being members of the
Academy.

In these the reader will find a luminous,
eminently simple, and popular account of the
discoveries of each of those distinguished indi-
viduals, of a "kind constituting in fact a brief
history of the particular branch of science to
which he was devoted. And in the selection
included in the present volume, which consti-
tutes but a portion of the entire series, we have
comprised the accounts of men of such varied
pursuits as to convey no inadequate impression
of the progress of discovery throughout a con-
siderable range of the whole field of the physi-
cal sciences within the last half century.

The account given by the author, of the prin-
cipal discoveries made by the illustrious subjects
of his memoirs, is in general very luminous,
but at the same time presupposes a familiarity
with some parts of science which may not
really be possessed by all readers. For the



TRANSLATORS' PREFACE. vii

sake of a considerable class, then, we have
taken occasion, wherever the use of new tech-
nical terms or other like circumstances seemed
to require it, to introduce original notes and
commentaries, sometimes of considerable extent,
by the aid of which we trust the scientific prin-
ciples adverted to in the text will be rendered
easily intelligible to the general reader.

In some few instances also we have found
ourselves called upon to adopt a more critical
tone ; where we were disposed to dissent from
the view taken by the author on particular
questions of a controversial kind, or when he
is arguing in support, or in refutation, of op-
posing theories on some points of science not
yet satisfactorily cleared up.

We could have wished that our duty as
translators and editors had not extended be-
yond such mere occasional scientific or literary
criticism. But there unfortunately seemed to
be one or two points where, in pronouncing on
the claims of distinguished individuals, or criti-
cizing their inventions, a doubt could not but
be felt as to the perfect fairness of Arago's
judgment, and in which we were constrained
to express an unfavourable opinion on the man-
ner in which the relative pretensions of men of
the highest eminence seemed to be decided, in-



viii TRANSLATORS' PREFACE.

volving what might sometimes be fairly re-
garded as undue prejudice, or possibly a feeling
of personal or even national jealousy. Much
as we should deprecate the excitement of any
feeling of hostility of this kind, yet we could
not, in our editorial capacity, shrink from the
plain duty of endeavouring to advocate what
appeared to us right and true j and we trust
that whatever opinion may be entertained as
to the conclusions to which we have come on
such points, we shall not have given ground
for any complaint that we have violated any
due courtesy or propriety in our mode of ex-
pressing those conclusions, or the reasons on
which they are founded.



CONTENTS.



THE HISTORY OF MY YOUTH.

PAGE

An Autobiography of Francis Arago 1

|

I BAILLY.

Introduction 91

Infancy of Bailly. His Youth. His Literary Essays.
His Mathematical Studies 93

Bailly becomes the Pupil of Lacaille. He is associated
with him in his Astronomical Labours 97

Bailly a Member of the Academy of Sciences. His Re-
searches on Jupiter's Satellites 103

Bailly's Literary Works. His Biographies of Charles V.
of Leibnitz of Peter Corneille of Moliere 106

Debates relative to the Post of Perpetual Secretary of
the Academy of Sciences 110

History of Astronomy. Letters on the Atlantis of Plato
and on the Ancient History of Asia 114

First Interview of Bailly with Franklin. His Entrance
into, the French Academy in 1783. His Reception.
Discourse. His Rupture with Buffon 121



X CONTENTS.

PAGE

Report on Animal Magnetism 127

Election of Bailly into the Academy of Inscriptions. ... 155

Report on the Hospitals 157

Report on the Slaughter-Houses 165

Biographies of Cook and of Gresset 167

Assembly of the Notables. Bailly is named First Deputy
of Paris ; and soon after Dean or Senior of the Depu-
ties of the Communes 169

Bailly becomes Mayor of Paris. Scarcity. Marat de-
clares himself inimical to the Mayor. Events of the

6th of October 179

A Glance at the Posthumous Memoir of Bailly 193

Examination of Bailly's Administration as Mayor 195

The King's Flight. Events on the Champ de Mars 206

Bailly quits the Mayoralty the 12th of November, 1791.
The Eschevins. Examination of the Reproaches

that might be addressed to the Mayor 211

Bailly's Journey from Paris to Nantes, and then from
Nantes to Melun. His Arrest in this last Town. He

is transferred to Paris 217

Bailly is called as a Witness in the Trial of the Queen.
His own Trial before the Revolutionary Tribunal.
His Condemnation to Death. His Execution. Imag-
inary Details added by ill-informed Historians to what

that odious and frightful Event already presented 225

Portrait of Bailly. His Wife 250

HERSCHEL.

Personal History 258

Chronological Table of the Memoirs of William Herschel 266

Improvements in the Means of Observation 271

Labours in Sidereal Astronomy 285






CONTENTS. XI

PAGE

Labours relative to the Solar System 289

Optical Labours 301

LAPLACE.
Preliminary Notice 303

APPENDIX.

(A.) Brief Notice of some other interesting Results
of the Researches of Laplace which have not

been mentioned in the Text 368

(B.) The Mecanique Celeste 372

V

1 JOSEPH FOURIER.

Preliminary Notice 374

Birth of Fourier. His Youth 377



Memoir on the Resolution of Numerical Equations 380

Part played by Fourier in our Revolution. His Entrance
into the Corps of Professors of the Normal School and

the Polytechnic School. Expedition to Egypt 384

Fourier Prefect of L'Isere 405

Mathematical Theory of Heat 408

Central Heat of the Terrestrial Globe 419

Return of Napoleon from Elba. Fourier Prefect of the
Rhone. His Nomination to the Office of Director of

the Board of Statistics of the Seine 430

Entrance of Fourier into the Academy of Sciences. His
Election to the Office of Perpetual Secretary. His

Admission to the French Academy 437

Character of Fourier. His Death 438



LIVES



OP



DISTINGUISHED SCIENTIFIC MEN.



THE HISTORY OF MY YOUTH:

AN AUTOBIOGRAPHY OF FRANCIS ARAGO.

I HAVE not the foolish vanity to imagine that any one,
even a short time hence, will have the curiosity to find
out how my first education was given, and how my mind
was developed ; but some biographers, writing off hand
and without authority, having given details on this sub-
ject utterly incorrect, and of a nature to imply negligence
on the part of my parents, I consider myself bound to
put them right.

I was born on the 26th of February, 1786, in the
commune of Estagel, an ancient province of Roussillon
(department of the Eastern Pyrenees). My father, a
licentiate in law, had some little property in arable land,
in vineyards, and in plantations of olive-trees, the income
from which supported his numerous family.

I was thus three years old in 1789, four years old in
1790, five years in 1791, six years in 1792, and seven

years old in 1793, &c.

1



2 AUTOBIOGRAPHY OF FRANCIS ARAGO.

The reader has now himself the means of judging
whether, as has been said, and even stated in print, I had
a hand in the excesses of our first revolution.

My parents sent me to the primary school in Estagel,
where I learnt the rudiments of reading and writing. I
received, besides, in my father's house, some private les-
sons in vocal music. I was not otherwise either more or
less advanced than other children of my age. I enter
into these details merely to show how much mistaken are
those who have printed that at the age of fourteen or fif-
teen years I had not yet learnt to read.

Estagel was a halting-place for a portion of the troops
who, coming from the interior, either went on to Perpig-
nan, or repaired direct to the army of the Pyrenees.
My parents' house was therefore constantly full of offi-
cers and soldiers. This, joined to the lively excitement
which the Spanish invasion had produced within me, in-
spired me with such decided military tastes, that my
family was obliged to have me narrowly watched to pre-
vent my joining by stealth the soldiers who left Estagel.
It often happened that they caught me at a league's dis-
tance from the village, already on my way with the
troops.

On one occasion these warlike tastes had nearly cost
me dear. It was the night of the battle of Peires-Tortes.
The Spanish troops in their retreat had partly mistaken
their road. I was in the square of the village before
daybreak ; I saw a brigadier and five troopers come up,
who, at the sight of the tree of liberty, called out, " So-
mos perdidos ! ' I ran immediately to the house to arm
myself with a lance which had been left there by a sol-
dier of the levee en masse, and placing myself in ambush
at the corner of a street, I struck with a blow of this



MATHEMATICAL STUDIES. O

weapon the brigadier placed at the head of the party.
The wound was not dangerous ; a cut of the sabre, how-
ever, was descending to punish my hardihood, when some
countrymen came to my aid, and, armed with forks, over-
turned the five cavaliers from their saddles, and made
them prisoners. I was then seven years old.*

My father having gone to reside at Perpignan, as treas-
urer of the mint, all the family quitted Estagel to follow
him there. I was then placed as an out-door pupil at the
municipal college of the town, where I occupied myself
almost exclusively with my literary studies. Our classic
authors had become the objects of my favourite reading.
But the direction of my ideas became changed all at
once by a singular circumstance which I will relate.

Walking one day on the ramparts of the town, I saw
an officer of engineers who was directing the execution
of the repairs. This officer, M. Cressac, was very
young ; I had the hardihood to approach him, and to ask
him how he had succeeded in so soon wearing an epau-
lette. "I come from the Polytechnic School," he an-
swered. " What school is that ? " " It is a school which
one enters by an examination." " Is much expected of
the candidates?" "You will see it in the programme
which the Government sends every year to the depart-
mental administration ; you will find it moreover in the
numbers of the journal of the school, which are in the
library of the central school."

I ran at once to the library, and there, for the first
time, I read the programme of the knowledge required
in the candidates.

* With such precocious heroism it is by no means so clear that the
author might not have had a hand in the revolution, from which he
endeavours above to exculpate himself.



4 AUTOBIOGRAPHY OF FRANCIS ARAGO.

From this moment I abandoned the classes of the cen-
tral school, where I was taiight to admire Corneille,
Racine, La Fontaine, Moliere, and attended only the
mathematical course. This course was entrusted to a re-
tired ecclesiastic, the Abbe Verdier, a very respectable
man, but whose knowledge w r ent no further than the ele-
mentary course of La Caille. I saw at a glance that M.
Verdier's lessons would not be sufficient to secure my ad-
mission to the Polytechnic School ; I therefore decided
on studying by myself the newest works, which I sent for
from Paris. These were those of Legendre, Lacroix,
and Gamier. In going through these works I often met
with difficulties which exceeded my powers ; happily,
strange though it be, and perhaps without example in all
the rest of France, there was a proprietor at Estagel, M.
Raynal, who made the study of the higher mathematics
his recreation. It was in his kitchen, whilst giving
orders to numerous domestics for the labours of the next
day, that M. Raynal read with advantage the " Hydraulic
Architecture '' of Prony, the " Mecanique Analytique,"
and the " Mecanique Celeste." This excellent man often
gave me useful advice ; but I must say that I found my
real master in the cover of M. Garnier's " Treatise on
Algebra." This cover consisted of a printed leaf, on the
outside of which blue paper was pasted. The reading of
the page not covered made me desirous to know what the
blue paper hid from me. I took off this paper carefully,
having first damped it, and was able to read underneath
it the advice given by d'Alembert to a young man who
communicated to him the difficulties which he met with
in his studies : " Go on, sir, go on, and conviction will
come to you."

This gave me a gleam of light ; instead of persisting



MATHEMATICAL STUDIES. 5

in attempts to comprehend at first sight the propositions
before me, I admitted their truth provisionally ; I went
on further, and was quite surprised, on the morrow, that
I comprehended perfectly what overnight appeared to me
to be encompassed with thick clouds.

I thus made myself master, in a year and a half, of all
the subjects contained in the programme for admission,
and I went to Montpellier to undergo the examination.
I was then sixteen years of age. M. Monge, junior, the
examiner, was detained at Toulouse by indisposition, and
wrote to the candidates assembled at Montpellier that he
would examine them in Paris. I was myself too unwell
to undertake so long a journey, and I returned to Per-
pignan.

There I listened for a moment to the solicitations of
my family, who pressed me to renounce the prospects
which the Polytechnic School opened. But my taste for
mathematical studies soon carried the day ; I increased
my library with Euler's " Introduction a 1' Analyse Infini-
te'simale," with the " Resolution des Equations Numeri-
ques," with Lagrange's " Theorie des Fonctions Analyti-
ques," and " Me'canique Analytique," and finally with
Laplace's " Mecanique Celeste." I gave myself up with
great ardour to the study of these books. From the jour-
nal of the Polytechnic School containing such investiga-
tions as those of M. Poisson on Elimination, I imagined
that all the pupils were as much advanced as this geome-
ter, and that it would be necessary to rise to this height
to succeed.

From this moment, I prepared myself for the artillery
service, the aim of my ambition ; and as I had heard
that an officer ought to understand music, fencing, and
dancing, I devoted the first hours of each clay to the cul-
tivation of these accomplishments.



6 AUTOBIOGRAPHY OF FRANCIS ARAGO.

The rest of the time I was seen walking in the moats
of the citadel of Perpignan, seeking by more or less
forced transitions to pass from one question to another, so
as to be sure of being able to show the examiner how far
my studies had been carried.*

At last the moment of examination arrived, and I
went to Toulouse in company with a candidate who had
studied at the public college. It was the first time that
pupils from Perpignan had appeared at the competition.
My intimidated comrade was completely discomfited.
When I repaired after him to the board, a very singular



* Me'chain, member of the Academy of Sciences and of the Insti-
tute, was charged in 1792 with the prolongation of the measure of the
arc of the meridian in Spain as far as Barcelona.

During his operations in the Pyrenees, in 1794, he had known my
father, who was one of the administrators of the department of the
Eastern Pyrenees. Later, in 1803, when the question was agitated as
to the continuation of the measure of the meridian line as far as the
Balearic Islands, M. Me" chain went again to Perpignan, and came to
pay my father a visit. As I was about setting off to undergo the ex-
amination for admission at the Polytechnic School, my father ventured
to ask him whether he could not recommend me to M. Monge. " Will-
ingly," answered he; "but, with the frankness which is my charac-
teristic, I ought not to leave you unaware that it appears to me im-
probable that your son, left to himself, can have rendered himself com-
pletely master of the subjects of which the programme consists. If,
however, he be admitted, let him be destined for the artillery, or for
the engineers ; the career of the sciences, of which you have talked
to me, is really too difficult to go through, and unless he had a special
calling for it, your son would only find it deceptive." Anticipating
a little the order of dates, let us compare this advice with what occur-
red : I went to Toulouse, underwent the examination, and was admit-
ted ; one year and a half afterwards I filled the situation of secretary
at the Observatory, which had become vacant by the resignation of
M. M ^chain's son; one year and a half later, that is to say, four years
after the Perpignan " horoscope," associated with M. Biot, I filled the
place, in Spain, of the celebrated academician who had died there, a
victim to his labours.



EXAMINATION BY M. MONGE. 7

conversation took place between M. Monge (the exami-
ner) and me.

" If you are going to answer like your comrade, it is
useless for me to question you."

" Sir, my comrade knows much more than he has
shown ; I hope I shall be more fortunate than he ; but
what you have just said to me might well intimidate me
and deprive me of all my powers."

"Timidity is always the excuse of 'the ignorant; it is
to save you from the shame of a defeat that I make you
the proposal of not examining you."

" I know of no greater shame than that which you now
inflict upon me. Will you be so good as to question me ?
it is your duty."

" You carry yourself very high, sir ! "We shall see
presently whether this be a legitimate pride."

" Proceed, sir ; I wait for you."

M. Monge then put to me a geometrical question,
which I answered in such a way as to diminish his pre-
judices. From this he passed on to a question in algebra,
to the resolution of a numerical equation. I had the
work of Lagrange at my fingers' ends ; I analyzed all
the known methods, pointing out their advantages and
defects ; Newton's method, the method of recurring series,
the method of depression, the method of continued frac-
tions, all were passed in review ; the answer had lasted
an entire hour. Monge, brought over now to feelings of
great kindness, said to me, " I could, from this moment,
consider the examination at an end. I will, however, for
my own pleasure, ask you two more questions. What
are the relations of a curved line to the straight line
which is a tangent to it ? " I looked upon this question
as a particular case of the theory of osculations which I



8 AUTOBIOGRAPHY OF FRANCIS ARAGO.

had studied in Legrange's " Fonctions Analytiques."
" Finally," said the examiner to me, " how do you de-
termine the tension of the various cords of which a
funicular machine is composed ? " I treated this prob-
lem according to the method expounded in the " Me-
canique Analytique." It was clear that Lagrange had
supplied all the resources of my examination.

I had been two hours and a quarter at the board.
M. Monge, going from one extreme to the other, got up,
came and embraced me, and solemnly declared that I
should occupy the first place on his list. Shall I confess
it ? During the examination of my comrade I had heard
the Toulousian candidates uttering not very favourable
sarcasms on the pupils from Perpignan ; and it was
principally for the sake of reparation to my native town
that M. Monge's behaviour and declaration transported
me with joy.

Having entered the Polytechnic School, at the end of
1803, I was placed in the excessively boisterous brigade
of the Gascons and Britons. I should have much liked
to study thoroughly physics and chemistry, of which I
did not even know the first rudiments ; but the behaviour
of my companions rarely left me any time for it. As
for analysis, I had already, before entering the Poly-
technic School, learnt much more than was required for
leaving it.

I have just related the strange words which M. Monge,
junior, addressed to me at Toulouse in commencing my
examination for admission. Something analogous oc-
curred at the opening of my examination in mathematics
for passing from one division of the school to another.
The examiner, this time, was the illustrious geometer
Legendre, of whom, a few years after, I had the honour
of becoming the colleague and the friend.



EXAMINATION BY M. LEGENDRE. 9

I entered his study at the moment when M. T ,

who was to undergo his examination before me, having
fainted away, was being carried out in the arms of two
servants. I thought that this circumstance would have
moved and softened M. Legendre ; but it had no such
effect. " What is your name," he said to me sharply.
" Arago," I answered. " You are not French then ? "
" If I was not French I should not be before you ; for I
have never heard of any one being admitted into the
school unless his nationality had been proved." " I
maintain that he 'is not French whose name is Arago."
" I maintain, on my side, that I am French, and a very
good Frenchman too, however strange my name may
appear to you." " Very well ; we will not discuss the
point farther ; go to the board."

I had scarcely taken up the chalk, when M. Legendre,
returning to the first subject of his preoccupations, said
to me : " You were born in one of the departments re-
cently united to France ? " " No, sir ; I was born in the
department of the Eastern Pyrenees, at the foot of the
Pyrenees." " Oh ! why did you not tell me that at once ?
all is now explained. You are of Spanish origin, are
you not ? ' : " Possibly ; but in my humble family there
are no authentic documents preserved which could enable
me to trace back the civil position of my ancestors ; each
one there is the child of his own deeds. I declare to you
again that I am French, and that ought to be sufficient
for you."

The vivacity of this last answer had not disposed M.
Legendre in my favour. I saw this very soon ; for, hav-
ing put a question to me which required the use of
double integrals, he stopped me, saying : " The method

which you are following was not given to you by the

1*



10 AUTOBIOGRAPHY OP FRANCIS ARAGO.

professor. Whence did you get it ? ' : " From one of
your papers." " Why did you choose it ? was it to bribe
me ? r " No ; nothing was farther from my thoughts.
I outy adopted it because it appeared to me preferable."
" If you are unable to explain to me the reasons for your
preference, I declare to you that you shall receive a bad
mark, at least as to character."

I then entered upon the details which established, as I
thought, that the method of double integrals was in all
points more clear and more rational than that which
Lacroix had expounded to us in the amphitheatre.
From this moment Legendre appeared to me to be sat-
isfied, and to relent.

Afterwards, he asked me to determine the centre of



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