THE STRUGGLE FOR MEANS TO WORK. THE
BURDEN OF CELEBRITY. THE FIRST ASSISTANCE
FROM THE STATE. IT COMES TOO LATE
In spite of our desire to concentrate our entire effort on the work in
which we were engaged, and in spite of the fact that our needs were so
modest, we were forced to recognize, toward 1900, that some increase in
our income was indispensable. Pierre Curie had few illusions about his
chances of obtaining an important chair in the University of Paris,
which would, even though it meant no large salary, have sufficed for the
small needs of our family, and enabled us to live without a
supplementary revenue. Since he was neither a graduate of the Normal
School nor of the Polytechnic, he lacked the support, often decisive,
which these big schools give their pupils; and the posts to which he
might justly have aspired, because of his achievements, were given to
others, without anyone's even thinking of him as a possible candidate.
At the beginning of 1898, he asked, without success, for the Chair of
Physical Chemistry left vacant by the death of Salet, and this failure
convinced him that he had no chance of advancement. He was appointed,
however, in March, 1900, to the position of assistant professor
(_répétiteur_) in the Polytechnic School, but he kept his post only
six months.
In the spring of 1900, there came an unexpected offer, that of the Chair
of Physics in the University of Geneva. The doyen of that University
made the invitation in the most cordial manner, and insisted that the
University was ready to make an exceptional effort to secure a scientist
of such high repute. The advantages of this position were that the
salary was larger than the average one, that it carried the promise of
the development of a Physics Laboratory adequate to our needs, and that
an official position for me would be provided in this laboratory. Such a
proposition merited a most careful consideration, so we made a visit to
the University of Geneva, where our reception was the most encouraging
possible.
This was a grave decision for us to make. Geneva presented material
advantages, and the opportunity of a life comparable in its tranquillity
with that in the country. Pierre Curie was, therefore, tempted to
accept, and it was only our immediate interest in our researches in
radium that made him finally decide not to. He feared the interruption
of our investigations which such a change must involve.
At this moment the Chair of Physics in the physics, chemistry and
natural history course at the Sorbonne, obligatory for students of
medicine, and familiarly known as P.C.N., was vacant; he applied, and
was appointed, due to the influence of Henri Poincaré, who was anxious
to free him from the necessity of quitting France. At the same time I
was given charge of the physics lectures in the Normal School for Girls
at Sèvres.
So we remained in Paris, and with our income increased. But we were at
the same time working under increasingly difficult conditions. Pierre
Curie was doing double teaching; and that in the P.C.N., with its very
large number of students, fatigued him greatly. As for myself, I had to
give much time to the preparation of my lectures at Sèvres, and to the
organization of the laboratory work there, which I found very
insufficient.
Moreover, Pierre Curie's new position did not bring with it a
laboratory; a little office and a single work room were all that he had
at his disposition in the annex (12 rue Cuvier) of the Sorbonne, which
served as teaching quarters for the P.C.N. And yet he felt it absolutely
necessary to go ahead with his own work. In fact, the rapid extension of
his investigations in radioactivity had made him determine that in his
new position at the Sorbonne he would receive students and start them in
research. He therefore took steps to find larger available working
quarters. Those who have taken similar steps realize the wall of
financial and administrative obstacles against which he was throwing
himself, and realize the large number of official letters, visits, and
of requests the least success entailed. All this thoroughly wearied and
discouraged Pierre Curie. He was obliged, too, constantly, to keep
traveling back and forth between the laboratories of the P.C.N. and the
hangar of the School of Physics where we still continued our work.
And besides these difficulties, we found that we could not make further
progress without the aid of industrial means of treating our raw
material. Fortunately certain expedients and generous assistance solved
this question.
As early as 1899 Pierre Curie succeeded in organizing a first industrial
experiment, using for it a chance installation placed at his disposition
by the Central Society of Chemical Products, with which he had had
relations in connection with the construction of his balances. The
technical details had been arranged very successfully by André
Debierne, and the operations brought good results, even though it had
been necessary to train a special personnel for this chemical work which
demanded special precautions.
Our investigations had started a general scientific movement, and
similar work was being undertaken in other countries. Toward these
efforts Pierre Curie maintained a most disinterested and liberal
attitude. With my agreement he refused to draw any material profit from
our discovery. We took no copyright, and published without reserve all
the results of our research, as well as the exact processes of the
preparation of radium. In addition, we gave to those interested whatever
information they asked of us. This was of great benefit to the radium
industry, which could thus develop in full freedom, first in France,
then in foreign countries, and furnish to scientists and to physicians
the products which they needed. This industry still employs to-day, with
scarcely any modifications, the processes indicated by us.[9]
Even though our industrial experiment yielded good results, again our
slender resources made it difficult to make further progress. Inspired
by our attempt, a French industrial, Armet de Lisle, had the idea, which
seemed daring at that epoch, of founding a veritable radium factory that
would furnish this product to physicians, whose interest in the
biological effects of radium and its possible therapeutic applications
had been aroused by the publication of various investigations. The
project proved a success because he could employ men already trained by
us in the delicate processes of this manufacture. Radium was then
regularly placed on sale, at a high price, it is true, because of the
special conditions under which it had to be made, and because, too, of
the immediate rise in the cost of the minerals necessary to its
production.[10]
I should like to express, here, our appreciation of the spirit in which
Armet de Lisle offered to cooperate with us. In an entirely
disinterested manner he placed at our disposition a little working place
in his factory and a part of the means necessary for us to use it. Other
funds were added either by ourselves, or came through subventions, of
which the most important, accorded in 1902 by the Academy of Sciences,
amounted to 20,000 francs.
It was in this way that we were able to utilize the ore we had acquired
little by little in the preparation of a certain quantity of radium,
which we used constantly in our research. The radium-bearing barium was
extracted in the factory, and I carried on its purification and
fractional crystallization in the laboratory. In 1902 I succeeded in
preparing a decigramme of chloride of pure radium which gave only the
spectrum of the new element, radium. I made a first determination of the
atomic weight of this new element, an atomic weight much higher than
that of barium. Thus the chemical individuality of radium was completely
established, and the reality of radioelements was a known fact about
which there could be no further controversy.
I based my doctor's thesis, presented in 1903, on these investigations.
Later, the quantity of radium extracted for the laboratory was
increased, and in 1907 I was able to make a second and more precise
determination of the atomic weight as 225.35--one accepts now the number
226. I succeeded, too, jointly with André Debierne, in obtaining radium
in the state of metal. The total quantity of radium I prepared and gave
to the laboratory, in agreement with Pierre Curie's desire, amounted to
more than a gramme of radium element.
The activity of pure radium exceeded all our expectations. For equal
weights this substance emits a radiation more than a million times more
intense than uranium. To offset this, the quantity of radium contained
in uranium minerals is scarcely more than three decigrammes of radium to
the ton of uranium. There is a very close relation between these two
substances. In fact, we know to-day that radium is produced in the
minerals at the expense of uranium.
The years that followed his nomination to the P.C.N. were hard for
Pierre Curie. He had to face the many anxieties incident to the
organization of a complicated system of work when his happiness depended
on his being able to concentrate his efforts on a single determined
subject. The physical fatigue due to the numerous courses he was obliged
to give was so great that he suffered from attacks of acute pain, which
in his overtaxed condition became more and more frequent.
It was therefore vitally important, if he was to spare his energy and
keep his health, that the burden of his professional duties be
lightened. He decided to apply for the Chair of Mineralogy, which was
vacant, at the Sorbonne, for which he was entirely qualified because of
his profound knowledge and his important publications on the theories of
the physics of crystals. Yet his candidacy failed.
During this painful period he nevertheless managed, by a truly
superhuman effort, successfully to complete and publish several
investigations that he had made either alone or in collaboration:
Investigations on induced radioactivity (in collaboration
with A. Debierne).
Investigations on the same subject (in collaboration
with J. Danne).
Investigations on the conductibility provoked in
dielectric liquids by the rays of radium and the
Roentgen rays.
Investigations on the law of the decrease of the
emanation of radium and on the radioactive
constants that characterize this emanation and
its active deposit.
Discovery of the liberation of heat produced by
radium (in collaboration with A. Laborde).
Investigations on the diffusion of the emanation of
radium in the air (in collaboration with J.
Danne).
Investigation on the radioactivity of gases from
thermal springs (in collaboration with A.
Laborde).
Investigation on the physiological effects of
radium rays (in common with Henri Becquerel).
Investigation on the physiological action of the
radium emanation (in common with Bouchard
and Balthazard).
Notes on the apparatus for the determination of
magnetic constants (in common with C. Cheneveau).
All these investigations in radioactivity are fundamental and touch very
varied subjects. Several have as their aim the study of the emanation,
that strange gaseous body that radium produces and which is largely
responsible for the intense radiation commonly attributed to the radium
itself. Pierre Curie demonstrated by a searching examination the
rigorous and invariable law according to which the emanation destroys
itself, no matter what the conditions are in which it finds itself.
To-day the emanation of radium, harvested in tiny phials, is commonly
employed by physicians as a therapeutic agent. Technical considerations
make its employment preferable to the direct use of radium, and in this
case no physician can proceed without consulting the numerical chart
which tells how much of this emanation has disappeared each day, despite
the fact that it is cloistered in its little glass prison. It is this
same emanation that is found in small quantities in mineral waters, and
that plays a part in their curative effects.
More striking still was the discovery of the discharge of heat from
radium. Without any alteration in appearance this substance releases
each hour a quantity of heat sufficient to melt its own weight of ice.
When well protected against this external loss, radium heats itself. Its
temperature can rise 10 degrees or more above that of the surrounding
atmosphere. This defied all contemporary scientific experience.
Finally, I cannot pass in silence, because of their various
repercussions, the experiments connected with the physiological effects
of radium.
In order to test the results that had just been announced by F. Giesel,
Pierre Curie voluntarily exposed his arm to the action of radium during
several hours. This resulted in a lesion resembling a burn, that
developed progressively and required several months to heal. Henri
Becquerel had by accident a similar burn as a result of carrying in his
vest pocket a glass tube containing radium salt. He came to tell us of
this evil effect of radium, exclaiming in a manner at once delighted and
annoyed: "I love it, but I owe it a grudge!"
Since he realized the interest in these physiological effects of radium,
Pierre Curie undertook, in collaboration with physicians, the
investigations to which I have just referred, submitting animals to the
action of radium emanation. These studies formed the point of departure
in radium therapy. The first attempts at treatment with radium were made
with products loaned by Pierre Curie, and had as their object the cure
of lupus and other skin lesions. Thus radium therapy, an important
branch of medicine, and frequently designated as _Curietherapie_, was
born in France, and was developed first through the investigations of
French physicians (Danlos, Oudin, Wickham, Dominici, Cheron, Degrais,
and others).[11]
In the meantime the great impetus given to the study of radioactivity
abroad led to a rapid succession of new discoveries. Many scientists
engaged in the search for other radio elements, using the new method of
chemical analysis, with the aid of radiation, that we had inaugurated.
Thus were found the mesothorium now used by physicians and manufactured
industrially, radio-thorium, ionium, protoactinium, radio-lead, and
other substances. At present we know, in all, about thirty radio
elements (among which three are gases, or emanations), but among them
all radium still plays the most important part, because of the great
intensity of its radiation, which diminishes only extremely slowly
during the course of years.
The year 1903 was especially important in the development of the new
science. In this year the investigation of radium, the new chemical
element, was achieved, and Pierre Curie demonstrated the astonishing
discharge of heat by this element, which nevertheless remained unaltered
in appearance. In England, Ramsay and Soddy announced a great discovery.
They proved that radium continually produces helium gas and under
conditions that force one to believe in an atomic transformation. If,
indeed, radium salt heated to its melting point is confined for some
time in a sealed glass tube, entirely emptied of air, one can, in
reheating it, make it throw off a small quantity of helium, easy to
measure and to recognize from the character of its spectrum. This
fundamental experiment has received numerous confirmations. It furnished
us the first example of a transformation of atoms, independent, it is
true, of our will, but at the same time it reduces to nothing the theory
of the absolute fixity of the atomic edifice.
All these facts, along with others formerly known, were made the object
of a synthesis of the highest value, in a work by E. Rutherford and F.
Soddy, who proposed a theory of radioactive transformations, to-day
universally adopted. According to this theory, each radio element, even
when it appears unchanged, is undergoing a spontaneous transformation,
and the more rapid the transformation, the more intense is the
radiation.[12]
A radioactive atom can transform itself in two ways: it can expel from
itself an atom of helium, which, thrown off at an enormous speed and
with a positive charge, constitutes an Alpha ray. Or, instead, it can
detach from its structure a much smaller fragment, one of those
electrons to which we have become accustomed in modern physics, and
whose mass, 1800 times smaller than that of an atom of hydrogen when its
speed is moderate, grows excessively when its speed approaches that of
light. These electrons, which carry a negative charge, form the Beta
rays. Whatever the detached fragment, the residual atom no longer
resembles the primitive atom. Thus when the atom of radium has expelled
an atom of helium, the residue is an atom of gaseous emanation. This
residue changes in its turn, and the process is not arrested until the
attainment of a last residue which is stable and does not give off any
radiation. This stable matter is inactive matter.
Thus the Alpha and Beta rays result from the fragmentation of atoms.
Gamma-rays are a radiation analogous to light, which accompanies the
cataclysm of the atomic transformation. They are very penetrating, and
are the ones most used in the therapeutic methods so far developed.[13]
We can see in all this that radio elements form families, in which each
member derives from a preceding member by direct descent the primary
elements being uranium and thorium. We can in particular prove that
radium is a descendant of uranium, and that polonium is a descendant of
radium. Since each radio element, at the same time that it is formed by
the mother substance, destroys itself, it cannot accumulate in the
presence of this mother substance beyond a determined proportion, which
explains why the relation between radium and uranium remains constant in
the very ancient unaltered minerals.
The spontaneous destruction of radio elements takes place according to a
fundamental law, called the _exponential law_, according to which the
quantity of each radio element diminishes by one-half in a time always
the same, called a period, this time-period making it possible to
determine without ambiguity the element under consideration. These
periods, which can be measured by diverse methods, vary greatly. The
period of uranium is several billions of years; that of radium is about
1600 years; that of its emanation a little less than four days; and
there are among the following descendants some whose period is the small
fraction of a second. The exponential law has a profound philosophic
bearing; it indicates that the transformation is produced according to
the laws of probability. The causes that determine the transformation
are a mystery to us, and we do not yet know if they derive from causal
conditions outside the atom, or from conditions of internal instability.
In many cases, up to the present, no exterior action has shown itself
effective in influencing the transformation.
This rapid succession of discoveries which overthrew familiar scientific
conceptions long held in physics and chemistry did not fail to meet, at
first, with doubts and incredulity. But the great part of the scientific
world received them with enthusiasm. At the same time Pierre Curie's
fame grew in France and in foreign countries. Already in 1901 the
Academy of Sciences had awarded him the Lacaze prize. In 1902, Mascart,
who had many times given him most valuable aid, decided to propose him
as a member of the Academy of Sciences. It was not easy for Pierre Curie
to agree to this, believing, as he did, that the Academy should elect
its members without the necessity of any preliminary solicitation or
paying of calls. Nevertheless, because of the friendly insistence of
Mascart, and above all because the Physics Section of the Academy had
already declared itself unanimously in his favor, he presented himself.
In spite of this, however, he failed of election, and it was only in
1905 that he became a member of the Institute, a membership which did
not last even a year. He was also elected to several academies and
scientific societies in other countries, and given an honorary doctor's
degree by several universities.
During 1903 we went to London at the invitation of the Royal
Institution, before which my husband was to lecture on radium. On this
occasion he had a most enthusiastic reception. He was especially happy
to see here again Lord Kelvin, who had always expressed an affection for
him, and who, despite his advanced age, preserved an interest,
perennially young, in science. The illustrious scientist showed, with
touching satisfaction, a glass vial containing a grain of radium salt
that Pierre Curie had given him. We met here also other celebrated
scientists, as Crookes, Ramsay, and J. Dewar. In collaboration with the
latter, Pierre Curie published investigations on the discharge of heat
by radium at very low temperatures, and upon the formation of helium in
radium salt.
A few months later the Davy medal was conferred upon him (and also upon
me) by the Royal Society of London, and at almost the same time, we
received, together with Henri Becquerel, the Nobel prize for physics.
Our health prevented us from attending the ceremony for the awarding of
this prize in December, and it was only in June, 1905, that we were able
to go to Stockholm where Pierre Curie gave his Nobel lecture. We were
most cordially received and had the felicity of seeing the admirable
Swedish nature in its most brilliant aspect.
The award of the Nobel prize was an important event for us because of
the prestige carried by the Nobel foundation, only recently founded
(1901). Also, from a financial point of view, the half of the prize
represented an important sum. It meant that in the future Pierre Curie
could turn over his teaching in the School of Physics to Paul Langevin,
one of his former students, and a physicist of great competence. He
could also engage a preparator to aid him in his work.
But at the same time the publicity this very happy event entailed bore
very heavily on a man who was neither prepared for it, nor accustomed to
it. There followed an avalanche of visits, of letters, of demands for
articles and lectures, which meant a constant enervation, fatigue, and
loss of time. He was kind and did not like to refuse a request; but on
the other hand, he had to recognize that he could not accede to the
solicitations that overwhelmed him without disastrous results to his
health, as well as to his peace of mind, and his work. In a letter to
Ch. Ed. Guillaume, he said:
"People ask me for articles and lectures, and after a few years are
passed, the very persons who make these demands will be astonished to
see that we have not accomplished any work."
And in other letters of the same period, written to E. Gouy, he
expressed himself as follows:
"20 March 1902
"As you have seen, fortune favors us at this moment; but these favors of
fortune do not come without many worries. We have never been less
tranquil than at this moment. There are days when we scarcely have time
to breathe. And to think that we dreamed of living in the wild, quite
removed from human beings!"
"22 January 1904
"MY DEAR FRIEND:
"I have wanted to write to you for a long time; excuse me if I have not
done so. The cause is the stupid life which I lead at present. You have
seen this sudden infatuation for radium, which has resulted for us in
all the advantages of a moment of popularity. We have been pursued by
journalists and photographers from all countries of the world; they have
gone even so far as to report the conversation between my daughter and
her nurse, and to describe the black-and-white cat that lives with
us.... Further, we have had a great many appeals for money.... Finally,
the collectors of autographs, snobs, society people, and even at times,
scientists, have come to see us--in our magnificent and tranquil
quarters in the laboratory--and every evening there has been a
voluminous correspondence to send off. With such a state of things I
feel myself invaded by a kind of stupor. And yet all this turmoil will
not perhaps have been in vain, if it results in my getting a chair and
a laboratory. To tell the truth, it will be necessary to create the
chair, and I shall not have the laboratory at first. I should have
preferred the reverse, but Liard wishes to take advantage of the present
moment to bring about the creation of a new chair that will later be
acquired for the university. They are to establish a chair without a
fixed program, which will be something like a course in the Collège de
France, and I believe I shall be obliged to change my subject each year,
which will be a great trial to me."
"31 January 1905
"... I have had to give up going to Sweden. We are, as you see, most
irregular in our relations with the Swedish Academy; but, to tell the
truth, I can only keep up by avoiding all physical fatigue. And my wife
is in the same condition; we can no longer dream of the great work days
of times gone by.
"As to research, I am doing nothing at present. With my course, my
students, apparatus to install, and the interminable procession of
people who come to disturb me without serious reason, the days pass
without my having been able to achieve anything useful at this end."
"25 July 1905
"MY DEAR FRIEND:
"We have regretted so much being deprived of your visit this year, but
hope to see you in October. If we do not make an effort from time to
time, we end by losing touch with our best and most congenial friends,
and in keeping company with others for the simple reason that it is easy
to meet them.
"We continue to lead the same life of people who are extremely occupied,
without being able to accomplish anything interesting. It is now more
than a year since I have been able to engage in any research, and I have
no moment to myself. Clearly I have not yet discovered a means to defend
ourselves against this frittering away of our time which is nevertheless
extremely necessary. Intellectually, it is a question of life or death."
"7 November 1905
"I begin my course tomorrow but under very bad conditions for the
preparation of my experiments. The lecture room is at the Sorbonne, and
my laboratory is in the rue Cuvier. Besides, a great number of other
courses are given in the same lecture room, and I can use it only one
morning for the preparation of my own.
"I am neither very well, nor very ill; but I am easily fatigued, and I
have left but very little capacity for work. My wife, on the contrary,
leads a very active life, between her children, the School at Sèvres,
and the laboratory. She does not lose a minute, and occupies herself
more regularly than I can with the direction of the laboratory in which
she passes the greater part of the day."
To sum up: despite these outside complications, our life, by a common
effort of will, remained as simple and as retired as formerly. Toward
the close of 1904 our family was increased by the birth of a second
daughter. Eve Denise was born in the modest house in Boulevard
Kellermann, where we still lived with Doctor Curie, seeing only a few
friends.
As our elder daughter grew up, she began to be a little companion to her
father, who took a lively interest in her education and gladly went for
walks with her in his free times, especially on his vacation days. He
carried on serious conversations with her, replying to all her questions
and delighting in the progressive development of her young mind. From
their early age, his children enjoyed his tender affection, and he never
wearied of trying to understand these little beings, in order to be able
to give them the best he had to give.
With his great success in other countries, the complete appreciation of
Pierre Curie in France, however tardily, did at last follow. At
forty-five he found himself in the first rank of French scientists and
yet, as a teacher, he occupied an inferior position. This abnormal state
of affairs aroused public opinion in his favor, and under the influence
of this wave of feeling, the director of the Academy of Paris, L. Liard,
asked Parliament to create a new professorship in the Sorbonne, and at
the beginning of the academic year 1904-05 Pierre Curie was named
titular professor of the Faculty of Sciences of Paris. A year later he
definitely quitted the School of Physics where his substitute, Paul
Langevin, succeeded him.
This new professorship was not established without a few difficulties.
The first project had provided for a new chair, but not for a
laboratory. And Pierre Curie felt that he could not accept a situation
which involved the risk of losing even the mediocre means of work that
he then had, instead of offering better ones. He wrote, therefore, to
his chiefs, that he had decided to remain at the P.C.N. His firmness won
the day. To the new chair was added a fund for a laboratory and
personnel for the new work (a chief of laboratory, a preparator, and a
laboratory boy). The position of chief of laboratory was offered to me,
which was a cause of very great satisfaction to my husband.
It was not without regret that we left the School of Physics, where we
had known such happy work days, despite their attendant difficulties. We
had become particularly attached to our hangar, which continued to
stand, though in a state of increasing decay, for several years, and we
went to visit it from time to time. Later it had to be pulled down to
make way for a new building for the Physics School, but we have
preserved photographs of it. Warned of its approaching destruction by
the faithful Petit, I made my last pilgrimage there, alas, alone. On the
blackboard there was still the writing of him who had been the soul of
the place; the humble refuge for his research was all impregnated with
his memory. The cruel reality seemed some bad dream; I almost expected
to see the tall figure appear, and to hear the sound of the familiar
voice.
Even though Parliament had voted the creation of a new chair, it did not
go so far as to consider the simultaneous founding of a laboratory which
was, nevertheless, necessary to the development of the new science of
radioactivity. Pierre Curie therefore kept the little workroom at the
P.C.N., and secured as a temporary solution of his difficulty the use of
a large room, then not being used by the P.C.N. He arranged, too, to
have a little building consisting of two rooms and a study set up in the
court.
One cannot help feeling sorrow in realizing that this was a last
concession, and that actually one of the first French scientists never
had an adequate laboratory to work in, and this even though his genius
had revealed itself as early as his twentieth year. Without doubt if he
had lived longer, he would have had the benefit of satisfactory
conditions for his work, but he was still deprived of them at his death
at the premature age of forty-eight. Can we fully imagine the regret of
an enthusiastic and disinterested worker in a great work, who is
retarded in the realization of his dream by the constant lack of means?
And can we think without a feeling of profound grief of the waste--the
one irreparable one--of the nation's greatest asset: the genius, the
powers, and the courage of its best children?
Pierre Curie had always in mind his urgent need for a good laboratory.
When, because of his great reputation, his chiefs felt obliged to try to
induce him, in 1903, to accept the decoration of the Légion d'Honneur,
he declined that distinction, remaining true to the opinion already
referred to in a preceding chapter. And the letter he wrote on this
occasion was inspired by the same feeling as that in the one previously
quoted, when he wrote to his director to refuse the _palmes
académiques_. I quote an extract:
"I pray you to thank the Minister, and to inform him that I do not in
the least feel the need of a decoration, but that I do feel the greatest
need for a laboratory."
After he was named professor at the Sorbonne, Pierre Curie had to
prepare a new course. The position had been given a very personal
character and a very general scope. He was left great freedom in the
choice of the matter he would present. Taking advantage of this freedom
he returned to a subject that was dear to him, and devoted part of his
lectures to the laws of symmetry, the study of fields of vectors and
tensors, and to the application of these ideas to the physics of
crystals. He intended to carry these lessons further, and to work out a
course that would completely cover the physics of crystallized matter
which would have been especially useful because this subject was so
little known in France. His other lessons dealt with radioactivity, set
forth the discoveries made in this new domain, and the revolution they
had caused in science.
Even though he was very much absorbed in the preparation of his course,
and often ill, my husband continued, nevertheless, to work in the
laboratory, which was becoming better and better organized. He had a
little more space now, and could receive a few students. In
collaboration with A. Laborde, he carried on investigations in mineral
waters and gases discharged from springs. This was the last work he
published.
His intellectual faculties were at this time at their height. One could
but admire the surety and rigor of his reasoning on the theories of
physics, his clear comprehension of fundamental principles, and a
certain profound sense of phenomena which he had by instinct, but which
he perfected during the course of a life entirely consecrated to
research and reflection. His skill in experiment, remarkable from the
beginning, was increased by practice. He experienced the pleasure of an
artist when he succeeded with a delicate installation. He enjoyed, too,
devising and constructing new apparatus, and I used jokingly to tell him
that he would not be happy unless he made at least an attempt of this
kind once every six months. His natural curiosity and vivid imagination
pushed him to undertakings in very varied directions; he could change
the object of his research with surprising ease.
He was scrupulously careful of scientific probity and of complete
accuracy in his publications. These are very perfect in form, and none
the less so in those parts where he applies the critical spirit to
himself, expressing his determination never to affirm anything that does
not seem entirely clear. He expresses his thought on this point in the
following words:
"In the study of unknown phenomena, one can make very general hypotheses
and then advance step by step with the help of experience. This method
of progress is sure but necessarily slow. One can, on the contrary, make
daring hypotheses in which he specifies the mechanism of phenomena. Such
a method of procedure has the advantage of suggesting certain
experiments, and, above all, of facilitating reasoning by rendering it
less abstract through the employment of an image. But on the other hand,
one cannot hope thus to conceive a complex theory in accord with
experiment. The precise hypothesis almost certainly includes a portion
of error along with a portion of truth. And this last portion, if it
exists, forms only a part of a more general proposition to which it will
be necessary in the end to return."
Moreover, even though he never hesitated to make hypotheses, he never
permitted their premature publication. He could never accustom himself
to a system of work which involved hasty publications, and was always
happier in a domain in which but a few investigators were quietly
working. The considerable vogue of radioactivity made him wish to
abandon this field of research for a time, and to return to his
interrupted studies of the physics of crystals. He dreamed also of
making an examination of diverse theoretical questions.
He gave much thought to his teaching, which constantly improved, and
which suggested to him ideas on the general orientation of studies and
on methods of teaching, which he believed should be based on contact
with experience and nature. He hoped to see his views adopted by the
Association of Professors as soon as it was formed, and to obtain the
declaration "that the teaching of the sciences must be the dominant
teaching of both the boys' and girls' lycées."
"But," he said, "such a notion would have little chance of success."
But this last period of his life, so fecund, was, alas, soon to end. His
admirable scientific career was to be suddenly broken at the very moment
when he could hope that the years of work to come would be less hard
than those which had preceded.
In 1906, quite ill and tired, he went with me and the children to spend
Easter in the Chevreuse Valley. Those were two sweet days under a mild
sun, and Pierre Curie felt the weight of weariness lighten in a healing
repose near to those who were dear to him. He amused himself in the
meadows with his little girls, and talked with me of their present and
their future.
He returned to Paris for a reunion and dinner of the Physics Society.
There he sat beside Henri Poincaré and had a long conversation with him
on methods of teaching. As we were returning on foot to our house, he
continued to develop his ideas on the culture that he dreamed of, happy
in the consciousness that I shared his views.
The following day, the 19th of April, 1906, he attended a reunion of the
Association of Professors of the Faculties of the Sciences, where he
talked with them very cordially about the aims which the Association
might adopt. As he went out from this reunion and was crossing the rue
Dauphine, he was struck by a truck coming from the Pont Neuf, and fell
under its wheels. A concussion of the brain brought instantaneous death.
So perished the hope founded on the wonderful being who thus ceased to
he. In the study room to which he was never to return, the water
buttercups he had brought from the country were still fresh.
[Footnote 9: During my recent visit to America, where a gramme of radium
was generously offered me by American women, the Buffalo Society of
Natural Sciences presented me, as a souvenir, with a publication
reviewing the development of the radium industry in the United States.
This included photographic reproductions of letters from Pierre Curie in
which he replied in as complete a manner as possible to the questions
asked by American engineers. (1902 and 1903.)]
[Footnote 10: The price of a milligramme of the element of radium was
then fixed at about 750 francs.]
[Footnote 11: These physicians were aided by the manufacturer, Armet de
Lisle, who placed at their disposition the radium needed for their first
undertakings. He founded, besides, in 1906, a laboratory for clinical
study, provided with a supply of radium. And he subventioned the first
special publication devoted to radioactivity and its applications, as a
journal under the name _Radium_, edited by J. Danne. This is an example
of generous support of science by industry, in reality still very rare
but which one wishes might become general, in the common interest of
these two branches of human activity.]
[Footnote 12: The hypothesis according to which radioactivity is bound
up with the atomic transformation of elements was first envisaged by
Pierre Curie and by me, along with other possible hypotheses, before it
was utilized by E. Rutherford. (See _Revue Scientifique_, 1900, Mme.
Curie, etc.)]
[Footnote 13: By using the unusual energy of Alpha-rays E. Rutherford
has obtained recently the rupture of certain light atoms, like those of
nitrogen.]