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THE LIBRARIES




BIOGRAPHIES



DISTINGUISHED SCIENTIFIC MEN.



/^ COT.. COLL.

TJBRARY

N.YOKK.



yust Published.
ARAGO'S BIOGRAPHIES

OF

DISTINGUISHED SCIENTIFIC MEN.

FIRST SERIES ftl.OO.



BIOGRAPHIES



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.



SECOND SERIES.



BOSTON:
TICKNOR AND FIELDS.

M nccc LIX.



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






■5S"



TJBRAm:

N.YOIIK.



CONTENTS.



CARNOT.

PAQE

Childhood of Carnot. — His Education 1

Entrance of Carnot into the School of Mezieres as Sec-
ond Lieutenant of Engineers 8

Carnot a First Lieutenant on Service in Fortresses • • • • 9
The first Communication between Carnot and the Acad-
emy of Sciences. — Air-Balloons 10

Eloge of Vauban by Carnot. — His Discussions with M. de

Montalembert 13

Essay on Machines. — New Theorem on the Loss of

Power , 21

Carnot a Politician and one of the Judges of Louis XVI. 30
Carnot a Member of the Committee of Public Safety- • • 33
Carnot entrusted with the Organization and Direction of

our Armies 44

Carnot on the Field of Battle at Wattignies 50

Statistics of the Operations of the Armies 54

Carnot, named by Fourteen Departments, enters the
Council of the Elders, and then the Executive Direc-
tory. — Hoche sent to La Vendue, Moreau and Jourdan
to the Rhine, and Bonaparte to Italy 54



30805



vi CONTENTS.

PAGE

Publication of the Work entitled " Reflections on the

Metaphysics of the Infinitesimal Calculus " 60

Carnot being " Fructidorise " is obliged to recur to Flight.
— He is erased from the List of the Institute, and suc-
ceeded by General Bonaparte 65

18th Brumaire. — Return of Carnot to France. — His Nom-
ination to be Minister of War. — His Dismissal. — His

Appointment to the Tribunate ^S

Publication of the Geometry of Position 77

Carnot Inventor of a New System of Fortification 84

Publication of the Treatise on the Defence of Fortresses. 94

Carnot an Academician 95

Events of 1813. — Carnot appointed to the Command at

Antwerp ^^

Conduct of Carnot during the Hundred Days 100

Carnot in Exile.— His Death 102

Portrait of Carnot. — Anecdotes relative to his political
and private Life 104

MALUS.
Birth of Malus.— His Literary Education.— His Admis-
sion to the Polytechnic School 117

Egyptian Campaign. — Extracts from the Memoranda of

Malus 120

Marriage of Malus. — His Military Career 133

Memoir on Light. — Composed in Egypt 135

Treatise on Analytical Optics 138

Memoir on the Refractive Power of Opaque Bodies. ... 139
Malus gains the Prize proposed by the Academy for a

Mathematical Theory of Double Refraction 147

Discovery, of Polarization by Reflexion 148

Letter from Young to Malus 158



CONTENTS. Vll

PAGE

Invention of the Repeating Goniometer.. 160

Mains a Candidate for the Academy of Sciences.— Situa-
tions which he filled. — His Death 163

Character of Malus.— Maxims and Precepts.— Suscepti-
bility of Malus on Questions of Scientific Priority 167

FRESNEL.

Preliminary Notice 1^1

Infancy of Fresnel.— His Entrance into the Polytechnic
School and into the Corps of Bridges and Highways.—
His Deposition for having gone to join the Royal Army

at Palud 175

Fresnel's first Scientific Papers 183

Refraction 186

Interferences 202

Polarization 217

Principal Characteristics of the System of Emission and
of that of Waves.— Grounds on which Fresnel was led

to reject unreservedly the System of Emission 231

Light-Houses 263

Life and Character of Fresnel. — His Death 273

THOMAS YOUNG.

Preliminary Notice 280

Birth of Young. — His Childhood. — First Entrance on his

Scientific Career 282

Theory of Vision 291

Interferences 298

Egyptian Hieroglyphics. — History of the first Exact In-
terpretation given of them 313

Note by Translator 325

Miscellaneous Works of Dr. Young 329



Vin CONTENTS.

PAOK

Character of Young. — His Position as a Physician. — His

Engagement on the Nautical Almanac. — His Death- • 330
Note by the Author 350

JAMES WATT.

Preliminary Notice 351

Infancy and Youth of James Watt. — His Advancement
to the Appointment of Engineer to the University of

Glasgow 352

Principles of the Steam-Engine 362

History of the Steam-Engine in Ancient Times 366

History of the Steam-Engine in Recent Times 370

Modern Steam-Engine 379

Watt's Labours in the Steam-Engine 387

Machines considered relative to their Effect on the Wel-
fare of the Working Classes 407

Press for Copying Letters. — Heating by Steam. — Compo-
sition of Water. — Bleaching by the Aid of Chlorine. —
Essay on the Physiological Effects that may result from

Breathing various Gases 424

Watt in Private Life. — Details of Events and of his Dis-
position. — His Death. — Numerous Statues erected to

his Memory. — Reflections 441

Academic? 1 Titles with which Watt was invested 467

Appendij^. — Retranslation of an Historical Note by Lord
Brougham, on the Discovery of the Composition of
Water 469

Note by W. Fairbairn, F.R.S. F.G.S 481



LIVES



DISTINGUISHED SCIENTIFIC MEN.



CARNOT



BIOGRAPHY READ AT A PUBLIC ASSEMBLY OP THE ACAD-
EMY OF SCIENCES, ON THE 21ST OF AUGUST, 1837.



CHILDHOOD OF CARNOT. — HIS EDUCATION.

Lazare-Nicolas-Marguerite Carnot was born at
Nolay (Cote-d'Or), in the ancient dncliy of Burgundy
that had ah-eady been the cradle of three of the greatest
ornaments of which the Academies could boast : Bossuet,
Vauban, and Buffon. His father was an advocate, and
exercised that noble profession with a great deal of talent
(which is not uncommon) and with very great disinter-
estedness (which is said to be not so common). The
advocate, Claude- Abraham Carnot, had eighteen children ;
so that, according to the old adage, which promises pros-
perity to a numerous family, he might expect a happy
future for each of his children. Indeed, at one period,
he might have counted, in this numerous family, two lieu-
tenant-generals of the French armies ; a councillor at the

SEC. SEU. 1



2 CARNOT.

court of repeal ; an attorney-general of the cour royale ;
the directress of the hospice de Nolay ; a municipal mag-
istrate much esteemed whilst he was administering the
affairs of his corporation, and still more esteemed, if
possible, when, after twenty-three years' exercise of his
functions, he submitted to be brutally deposed sooner
than fail in his duty. I must mention that, like an alfec-
tionate and provident father, the advocate of Nolay had
not trusted unreservedly to the virtue of the proverb, but
always presided personally over the early education of
his sons. Lazare Carnot, the subject of this biography,
only left his father's house to go, as it was then called,
through his Rhetoric and Philosophy.

The childhood of those privileged men who, under
various claims, have acted a brilliant part on the stage
of the world, has always attracted the attention of every
biographer. The "know thyself" of an ancient philos-
opher would be but poorly interpreted if only looked on
as a maxim of prudence ; the maxim is susceptible of a
juster and wider interpretation : it presents to us, I think,
the whole human race, as a body, for the most important
species of study that we can undertake. Therefore,
Gentlemen, let us carefully examine how those extraor-
dinary minds are indicated, are born, and grow, which,
on their complete development, are destined to open out
for themselves unknown paths. These characteristics
should be collected Avith all the more interest, because
they become daily more rare. In our modern schools,
modelled on exactly the same pattern from north to south
and from east to west ; subjected to the same regulations
and to a uniform discipline ; where children enter more-
over at the age of nine or ten years, and do not leave
until they are eighteen or twenty, individual character is



JUVENILE CA.REER. 3

effaced, or disappears, or is covered with the mask of
conventionality. The agricuUurist Avoald never go into
a hothouse to learn the character, the form, or the
appearance of those admirable plants which are the
ornament of our ancient forests. Neither is it in our
regiments that one might hope to trace out the true
types of the peasants of Brittany, Normandy, Lorraine,
or Franche-Comte. Our " school-regiments " (if I may
be allowed the expression) would lead moralists quite as
much astray. There, a sort of mean is established, about
which, with very slight variations, all the youth of the
present day is grouped. Is this for good or for evil?
Far be it from me to open such a discussion here ; I
merely say that such is the fact, and this fact will explain
why I have collected various particulars of the childhood
of our colleague, which might otherwise have appeared
trifliug.

Carnot was only ten years old when his mother, in a
journey to Dijon, took him with her, and, to reward him
for the thoughtful docility which he always showed, took
him to the theatre. A piece was represented that day,
in which evolutions of troops and battles succeeded one
another without intermission. The young scholar fol-
lowed with sustained attention the series of events which
were developed before him ; but, all on a sudden, he gets
up, he is agitated, and, in spite of the endeavours of his
mother, calls out in terms hardly polite, to an actor who
had just come on the stage. This person was the acting
general of the troops on whose side the young Carnot
was interested ; by his cries, the child was warning the
unskilful chief that the artillery was badly placed ; that
the gunners, being without cover, must necessarily be
killed by the fii'st fire of musketry from the ramparts of



4 CAKNOT.

the fortress which they were about to attack ; that, on
the other hand, by establishing the battery behind a rock,
which he pointed out, both by word of mouth and by
gesture, the mei* would be much less exposed. The
astonished actors did not know what to do ; Madame
Carnot was disti'essed at the disturbance which her son
was occasioning ; the audience burst out laughing ; every
one was puzzled as to the cause of such an unusual criti-
cism ; and the supposed frolic was nothing else than the
revelation of a superior military talent, the first symptom
of that powerful genius which, despising beaten tracks,
created, a few years later, new tactics, and proposed to
replace the scientifically and ingeniously combined forti-
fications of Vauban, by an altogether different system.

From the age of twelve to fifteen, Carnot pursued the
course of studies at the College at Autun. He made
himself remarkable there by a lively, original turn of
mind, and by a rare degree of intelligence. He next en-
tered the " little seminary " of the same town. At six-
teen years of age he had finished his Philosophy. The
firmness which we shall find in him in the course of a
most stormy career, was already the leading feature in
his character. The timid professoi's of the seminary of
Autun, had a troublesome experience of it on the day
when their scholar had to support his thesis.

This ceremony always took place in public. Accord-
in"' to regulations, the liberality of which would, at the
present day, appear excessive to the authorities of our
universities, every one of the audience had the right of
making objections. This criticism might be applied both
to the principles and to the style. Thus the amour pi-opre
of the master ran as much risk as that of the pupil, and
the reputation of a large establishment lay at the mercy



JUVENILE CAREER. 5

of some lioedless young fellow. Thenee came the custom
of starting the competitors in the arena accompanied l)y
a Mentor, who came to the assistance of their treacherous
memories, and who, by a word put in at the proper mo-
ment, brought them back into the right path as soon as
they began to wander from it ; and the Mentor was often
himself drawn into the discussion on his own account.
According to this custom, the teachers of the Seminary of
Autun were proceeding towards the salle des exercises,
whei'e a lai'ge concourse of people was assembled, when
the young Carnot signified his intention to ascend to the
rostrum alone, that he would not be accompanied by a
prompter, that he would not keep at all to the routine
they had assigned him, and that he would speak alone or
not at all. This resolution was combated by alternate en-
treaties and threats, but in vain : they were obliged to
submit, whether they liked it or not, to this unprecedented
caprice of the pupil. However, the most brilliant success
soon justified it, even in the eyes of the irritated profes-
sors. A curious incident rendered the meeting remark-
able : a lady, the wife of a doctor of medicine, became the
most formidable adversary of the young rhetorician : she
argued against him, in Latin, with a force of logic, with
an ease, a gi-ace, and an elegance of expression, which
the more astonished Carnot and the audience, inasmuch
as no indiscreet display had hitherto made them even,
suspect that Madame I'llomme had carried her studies
farther than the Cuisiniere bourgeoise, the Almanack de
Idege, or the Petit Paroissien.

Carnot had so thoroughly taken, not only to the prin-
ciple of religion, but, moreover (and they are not the
same things), to the minute practices of devotion scrupu-
lously followed at the little seminary of Autun, that some



6 CARNOT.

of his friends thought at one time of putting him into
holy orders. They were strengthened in this idea by the
recollection of the great number of ecclesiastical dignita-
ries of which this honourable family could boast, amongst
whom figured canons, vicaires-ghieraux of the diocese of
Chalon, doctors of the Sorbonne, and an abbe of Citeaux.
However, the career of military engineer carried the day,
and young Carnot was sent to Paris to a special school,
there to prepare for his examination. The comrades
whom he met there had certainly not been brought up at
the Seminary ; for the profound piety of the new scholar,
of which he would by no means make a mysteiy, became
the subject of their continual sarcasms. Sai-casms are
not reasons. Carnot was not therefore staggered by
them ; but he felt the necessity of maturing, by reflection
and study, ideas and sentiments to which his pure and
candid soul had hitherto given itself up with perfect good-
will and confidence. Theology, then, became, for some
months, the only occupation of an apprenti-qfficier, or
military novice. No one can tell what was the effect of
these meditations ; for, at all periods of his life, Carnot
cai-efuUy avoided, even in the intimacy of the domestic
circle, any discussions, — nay, more, any simple conversa-
tions — I'clating to religion. We only know that he pro-
fessed principles now adopted by all good and enhghtened
minds. " Universal tolerance," said he, when, proscribed
and wandering in a foreign land, he had to ward off the
spiteful darts of calumny, — "universal tolerance, that is

the dogma which I decidedly profess I abhor

fanaticism, and I beheve that the fanaticism of irreligion,
brought into fashion by such men as Marat and Pere
Duchesne, is the most fatal of all. We must not kill men
to force them to believe : we must not kill them to pre-



JUVENILE career; 7

vent their believing ; let us compassionate the weaknesses
of others, since every one has his own ; and let us allow
prejudices to wear away by time when we cannot obviate
them by reason."

After theology, scientific studies, especially those of
geometry and algebra, had their turn, and, as at Nolay
and Autun, his success was rapid and brilliant. M. de
Longpre, director of the preparatory school, was ac-
quainted with D'Alembert. The illustrious geometer was
not above going amongst very young scholars, to encour-
age rising merit by his approbation. In one of his visits
he particularly distinguished Carnot, and addressed to
him flattering and prophetic words, which our colleague
would repeat with emotion, even during those periods
when fortune had rendered him one of the arbiters of the
destinies of Europe.

Perhaps this is an opportunity. Gentlemen, for re-
gretting that, in our society, such as half a century of
revolutions has made it, the personal intercourse which
formerly existed between the professors and distinguished
scholars of great schools, has totally disappeared, and has
become indeed, to a certain degree, impossible. Now-a-
days, at the hour set down in the programmes, illustrious
men of learning or of literature arrive in spacious am-
phitheatres. A crowd is waiting for them. During entire
hours, all that is profound, intricate, or new, in science or
literature, is developed with system, clearness, and elo-
quence ; but, the lesson finished, the professor retires,
without even knowing the names of those who have
listened to him. Nevertheless, in the midst of such an
audience (I will confine myself, Gentlemen, to a single
example), Fourcroy found, in an apothecary's boy who
had come furtively to hear him, the devoted, exact, in-



8 CARNOT.

defatigable, and ingenious cooperator whom, by these
traits, each of you has ah-eady recognized — he discovered
Vauquelin !

ENTRANCE OF CARNOT INTO THE SCHOOL OP ME-
ZIERES AS SECOND LIEUTP:NANT OP ENGINEERS.

At the time when Carnot quitted the estabhshment of
M. de Longpi'e, the " ordonnance " in virtue of wliich a
genealogist cooperated witli a geometer in the examina-
tion of the future oihcers of engineers was not in force.
In 1771 any Frenchman might still be admitted at the
school of Mezieres without showing any parchments, on
condition always that neither his father nor mother had
endeavoured to enrich their family and their country by
commerce or by manual labour. The young aspirant
displayed unusual mathematical knowledge before the
examiner, Bossut. His father, in obedience to the sad
exigencies of the period, proved on his part that no ship
of his had ever been to distant countries to exchange the
fruits of the French soil or of French industry, for pro-
ductions reserved by nature to other climates ; that his
hands had never put together the movable types of
Gutenberg, even for the purpose of reproducing the
Bible or the Gospel; that he had not personally co-
operated in the construction of any of those admirable
instruments which measure time, or which sound the
depths of space.

After legal proof of these negative merits, young
Carnot was declared of sufficiently good family to wear
an epaulette, and received without delay that of a second
lieutenant.

Decorated with this so-much-desired epaulette, Carnot,
at the age of eighteen years, came to the School of En-



A FIRST LIEUTENANT ON SERVICE. ■ 9

gineers. There, under the auspices of Monge, he doubt-
less cultivated descriptive geometry and the physical
sciences with his habitual success ; but on this point it
must be owned, we are reduced to mere conjecture ; for
in carrying to an extreme the natural desire to conceal
from strangers the knowledge, then but little spread,
of the art of making and destroying fortifications, the
celebrated school of M(^zieres had been made a sort of
conclave of which the secrets were never penetrated by
the profane.

CARNOT A FIRST LIEUTENANT ON SERVICE IN FOR-
TRESSES.

On the 12th of January, 1773, Carnot, having become
a first lieutenant, was sent to Calais. The works of a
place where the periodical oscillations of the ocean add
a new and important condition to the already very com-
plicated data of the problem of fortification, were very
interesting to the young officer. He thus overleaped
without hindrance, the passage, generally so troublesome,
from learned theories to tiresome practice ; from the
brilliant illusions which amuse us in schools, to the sad
realities of life.

The Memorial de Saint Helene says that in his youth
" Carnot was looked on by his comrades as an original."
This title Napoleon had borrowed from Carnot himself.
I find it in the answer to Bailleul, but explained and
commented on, and deprived of that vagueness which
leaves it to be taken either as a compliment or a reproach.
Carnot, at twenty years of age, was, to the officers of the
garrison of Calais, an " original," or a " philosojiher,"
(these words were equivalent,) because he did not join
them either in their turbulence or in any of their wild
1*



10 CARNOT.

pranks ; because he passed his time in the libraries
rather than at the cafe ; because, he read Thucydides,
Polybius, and Cnesav, rather than the licentious works of
that 2:)eriod ; because, if he were intimate with the Prince
de Croy, Commandant-General of Picardy, it was not for
the sake of obtaining leave from, or alleviations of, duty,
but in order to assist him in delicate geographical re-
searches, and to work at charts of the Southern Hemi-
sphere, showing the latest nautical discoveries. Carnot,
nevertheless, was anything but an ill-natured judge of
others. Severe towards himself, he had an inexhaustible
fund of indulgence to every one else. He employed his
hours of leisux'e or relaxation in composing little poems,
all impressed with a gentle and social gayety. To have
quoted ballads in the biography of a geometer would
certainly have had great novelty, and this weak merit,
quite within my grasp, had almost pei'suaded me to do
so ; a little reflection has caused me to give it up. A
great poet in our country having stamped that nature of
composition with his immortal seal, song should no longer
be lightly quoted.

THE FIRST COMMUNICATION BETWEEN CARNOT AND
THE ACADEMT OF SCIENCES. AIR-BALLOONS.

The first direct communication between Carnot and
the Academy of Sciences (this fact Avill be a novelty to
every one) was brought about by a problem which not
only has not yet been solved, but which, according to
many physical philosophers, appears as if it never can
be — " the problem of guiding balloons."

Scientific discoveries, "even those from which mankind
might expect the greatest advantages — such, for instance,
as those of the mariner's compass and the steam-engine^



ON AIR-BALLOONS. 11

were received on their first appearance with disdainful
indifference. PoUtical and military events exclusively
enjoy the privilege of exciting the public. There have
been, however, two exceptions to this rule. You will all
know by this hint, that I allude to America and aii - bal-
loons, Christopher Columbus and MontgoMer. The dis-
coveries of these two men of genius, so different hitherto
in their results, had, at their birth, similar fortunes.
Gather, in fact, from the Historia del Almirante the
marks of the general enthusiasm which the discovery of
certain islands excited amongst the Andalusians, the
Catalonians, the Arragonese, and the Castilians ; read
the account of the unheard-of honours which they hast-
ened to render, as well in the largest cities as in the
smallest hamlets, not only to the leader of the enterprise,
but even to the very sailors of the caravels La Santa
Maria, La Pinta, and La Nina, which were the first to
reach the western shores of the Atlantic ; you may then
save yourselves the trouble of searching in the writings
of the period what sort of sensation air-balloons pro-
duced amongst our compatriots : the processions at Se-
ville and Barcelona were faithful representations of the
fetes which took place at Lyons and Paz*is. In 1783,
just as it happened two centuries before, warm imagina-
tions were not at the trouble of confining themselves to
the limits of facts or of probabilities. In the one instance,
there was not a Spaniard who did not wish, after the ex-
ample of Columbus, himself also to tread lands where,
in a few days, he might collect as great a quantity of
gold and precious stones as was formerly the possession
of the richest potentates. In France each individual,
following the favourite direction of his ideas, made dif-
ferent but charming applications of the new faculty — I



12 CARNOT.

had almost said of the new organs — which man had just
I'eceived from the hands of Montgolfier. The {physical
philosopher, transported into the region of meteors, and
catching Nature in the act, penetrated at a glance the
mysteiy of the formation of lightning, of snow, and of



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