Читать книгу The life of Pasteur - René Vallery-Radot - Страница 8

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Pasteur often spent his leisure moments in the library of the Ecole Normale. Those who knew him at that time remember him as grave, quiet, almost shy. But under these reflective characteristics lay the latent fire of enthusiasm. The lives of illustrious men, of great scientists, of great patriots inspired him with a generous ardour. To this ardour he added a great eagerness of mind; whether studying a book, even a commonplace one—for he was so conscientious that he did not even know what it was to “skim” through a book—or coming away from one of J. B. Dumas’ lectures, or writing his student’s notes in his small fine handwriting, he was always thirsting to learn more, to devote himself to great researches. There seemed to him no better way of spending a holiday than to be shut up all Sunday afternoon at the Sorbonne laboratory or coaxing a private lesson from the celebrated Barruel, Dumas’ curator.

Chappuis—anxious to obey the injunctions of Pasteur’s father, who in every letter repeated “Do not let him work too much!” desirous also of enjoying a few hours’ outing with his friend—used to wait philosophically, sitting on a laboratory stool, until the experiments were over. Conquered by this patient attitude and reproachful silence Pasteur would take off his apron, saying half angrily, half gratefully, “Well, let us go for a walk.” And, when they were out in the street, the same serious subjects of conversation would inevitably crop up—classes, lectures, readings, etc.

One day, in the course of those long talks in the gardens of the Luxembourg, Pasteur carried Chappuis with him very far away from philosophy. He began to talk of tartaric acid and of paratartaric acid. The former had been known since 1770, thanks to the Swedish chemist Scheele, who discovered it in the thick crusty formations within wine barrels called “tartar”; but the latter was disconcerting to chemists. In 1820 an Alsatian manufacturer, Kestner, had obtained by chance, whilst preparing tartaric acid in his factory at Thann, a very singular acid which he was unable to reproduce in spite of various attempts. He had kept some of it in stock. Gay-Lussac, having visited the Thann factory in 1826, studied this mysterious acid; he proposed to call it racemic acid. Berzelius studied it in his turn, and preferred to call it paratartaric. Either name may be adopted; it is exactly the same thing: men of letters or in society are equally frightened by the word paratartaric or racemic. Chappuis certainly was when Pasteur repeated to him word for word a paragraph by a Berlin chemist and crystallographer named Mitscherlich. Pasteur had pondered over this paragraph until he knew it by heart; often indeed, absorbed in reading the reports for 1844 of the Académie des Sciences, in the dark room which was then the library of the Ecole Normale, he had wondered if it were possible to get over a difficulty which seemed insurmountable to scientists such as Mitscherlich and Biot. This paragraph related to two saline combinations—tartrate and paratartrate of soda or ammonia—and may be epitomized as follows: in these two substances of similar crystalline form, the nature and number of the atoms, their arrangement and distances are the same. Yet dissolved tartrate rotates the plane of polarized light and paratartrate remains inactive.

Pasteur had the gift of making scientific problems interesting in a few words, even to minds least inclined to that particular line of thought. He rendered his listener’s attention very easy; no question surprised him and he never smiled at ignorance. Though Chappuis, absorbed in the series of lectures on philosophy given at that time by Jules Simon, was deep in a train of thought very far away from Mitscherlich’s perplexities, he gradually became interested in this optical inactivity of paratartrate, which so visibly affected his friend. Pasteur liked to look back into the history of things, giving in this way a veritable life to his explanations. Thus, à propos of the optical phenomenon which puzzled Mitscherlich, Pasteur was speaking to his friend of crystallized carbonate of lime, called Iceland spar, which presents a double refraction—that is to say: if you look at an object through this crystal, you perceive two reproductions of that object. In describing this, Pasteur was not giving to Chappuis a vague notion of some piece of crystal in a glass case, but was absolutely evoking a vision of the beautiful crystal, perfectly pure and transparent, brought from Iceland in 1669 to a Danish physicist. Pasteur almost seemed to experience the surprise and emotion of this scientist, when, observing a ray of light through this crystal, he saw it suddenly duplicated. Pasteur also spoke enthusiastically of an officer of Engineers under the First Empire, Etienne Louis Malus. Malus was studying double refraction, and holding in his hands a piece of spar crystal, when, from his room in the Rue de l’Enfer, it occurred to him to observe through the crystal the windows of the Luxembourg Palace, then lighted up by the setting sun. It was sufficient to make the crystal rotate slowly round the visual ray (as on an axis) to perceive the periodic variations in the intensity of the light reflected by the windows. No one had yet suspected that light, after being reflected under certain conditions, would acquire properties quite different from those it had before its reflection. Malus gave the name of polarized light to light thus modified (by reflection in this particular case). Scientists admitted in those days, in the theory of emission, the existence of luminous molecules, and they imagined that these molecules “suffered the same effects simultaneously when they had been reflected on glass at a certain angle.... They were all turned in the same direction.” Pouillet, speaking of this discovery of Malus in the class on physics that Pasteur attended, explained that the consequent persuasion was “that those molecules had rotatory axes and poles, around which their movements could be accomplished under certain influences.”

Pasteur spoke feverishly of his regrets that Malus should have died at thirty-seven in the midst of his researches; of Biot, and of Arago, who became illustrious in the path opened by Malus. He explained to Chappuis that, by means of a polarizing apparatus, it could be seen that certain quartz crystals deflected to the right the plane of polarized light, whilst others caused it to turn to the left. Chappuis also learned that some natural organic material, such as solutions of sugar or of tartaric acid, when placed in such an apparatus, turned to the right the plane of polarization, whilst others, like essence of turpentine or quinine, deflected it to the left; whence the expression “rotatory polarization.”

These would seem dry researches, belonging altogether to the domain of science. And yet, thanks to the saccharimeter, which is a polarizing apparatus, a manufacturer can ascertain the quantity of pure sugar contained in the brown sugar of commerce, and a physiologist can follow the progress of diabetes.

Chappuis, who knew what powers of investigation his friend could bring to bear on the problem enunciated by Mitscherlich, thought with regret that the prospect of such examinations as that for the licence and for the agrégation did not allow Pasteur to concentrate all his forces on such a special scientific point. But Pasteur was resolved to come back definitely to this subject as soon as he should have become “docteur ès sciences.”

When writing to his father he did not dwell upon tartrate and paratartrate; but his ambition was palpable. He was ever eager to do double work, to go up for his examination at the very earliest. “Before being a captain,” answered the old sergeant-major, “you must become a lieutenant.”

These letters give one the impression of living amongst those lives, perpetually reacting upon each other. The thoughts of the whole family were centred upon the great School, where that son, that brother, was working, in whom the hopes of each were placed. If one of his bulky letters with the large post mark was too long in coming, his father wrote to reproach him gently: “Your sisters were counting the days. Eighteen days, they said! Louis has never kept us waiting so long! Can he be ill? It is a great joy to me,” adds the father, “to note your attachment to each other. May it always remain so.”

The mother had no time to write much; she was burdened with all the cares of the household and with keeping the books of the business. But she watched for the postman with a tender anxiety increased by her vivid imagination. Her thoughts were ever with the son whom she loved, not with a selfish love, but for himself, sharing his happiness in that he was working for a useful career.

So, between that corner in the Jura and the Ecole Normale, there was a continual exchange of thoughts; the smallest incidents of daily life were related. The father, knowing that he should inform the son of the fluctuations of the family budget, spoke of his more or less successful sales of leathers at the Besançon fair. The son was ever hunting in the progress of industry anything that could tend to lighten the father’s heavy handicraft. But though the father declared himself ready to examine Vauquelin’s new tanning process, which obviated the necessity of keeping the skins so long in the pits, he asked himself with scrupulous anxiety whether leathers prepared in that way would last as long as the others. Could he safely guarantee them to the shoemakers, who were unanimous in praising the goods of the little tannery-yard, but alas equally unanimous in forgetting to reward the disinterested tanner by prompt payment? He supplied his family with the necessaries of life: what more did he want? When he had news of his Normalien he was thoroughly happy. He associated himself with his son’s doings, sharing his enthusiasm over Dumas’ lectures, and taking an interest in Pouillet’s classes: Pouillet was a Franc-Comtois, and had been a student at the Ecole Normale; he was now Professor of Physics at the Sorbonne and a member of the Institut.[10] When Balard, a lecturer at the Ecole, was nominated to the Académie des Sciences, Louis told his father of it with the delight of an admiring pupil.

Like J. B. Dumas, Balard had been an apothecary’s pupil. When he spoke of their humble beginnings, Dumas was wont to say rather pompously—“Balard and I were initiated into our scientific life under the same conditions.” When, at the age of forty-two, he was made a member of the Institute, Balard could not contain his joy; he was quite a Southerner in his language and gestures, and the adjective exubérant might have been invented for him. But this same Southerner, ever on the move as he was, belonged to a special race: he always kept his word. “I was glad to note your pleasure at this nomination,” wrote Joseph Pasteur to his son; “it proves that you are grateful to your masters.” About that same time the headmaster of Arbois College, M. Romanet, used to read out to the older boys the letters, always full of gratitude, which he received from Louis Pasteur. These letters reflected life in Paris, such as Pasteur understood it—a life of hard work and exalted ambition. M. Romanet, in one of his replies, asked him to become librarian in partibus for the college and to choose and procure books on science and literature. The headmaster also begged of the young man some lectures for the rhétorique class during the holidays. “It would seem to the boys like an echo of the Sorbonne lectures! And you would speak to us of our great scientific men,” added M. Romanet, “amongst whom we shall one day number him who once was one of our best pupils and will ever remain one of our best friends.”

A corresponding member of Arbois College, and retained as vacation lecturer, Pasteur now undertook a yet more special task. He had often heard his father deplore his own lack of instruction, and knew well the elder man’s desire for knowledge. By a touching exchange of parts, the child to whom his father had taught his alphabet now became his father’s teacher; but with what respect and what delicacy did this filial master express himself! “It is in order that you may be able to help Josephine that I am sending you this work to do.” He took most seriously his task of tutor by correspondence; the papers he sent were not always easy. His father wrote (Jan. 2, 1845)—“I have spent two days over a problem which I afterwards found quite easy; it is no trifle to learn a thing and teach it directly afterwards.” And a month later: “Josephine does not care to rack her brains, she says; however I promise you that you will be pleased with her progress by the next holidays.”

The father would often sit up late at night over rules of grammar and mathematical problems, preparing answers to send to his boy in Paris.

Some Arboisians, quite forgotten now, imagined that they would add lustre to the local history. General Baron Delort, a peer of France,[11] aide de camp to Louis Philippe, Grand Cross of the Legion of Honour and the first personage in Arbois—where he beguiled his old age by translating Horace—used to go across the Cuisance bridge without so much as glancing at the tannery where the Pasteur family lived. Whilst the general in his thoughts bequeathed to the town of Arbois his books, his papers, his decorations, even his uniform, he was far from foreseeing that the little dwelling by the bridge would one day become the cynosure of all eyes.

Months went by and happy items of news succeeded one another. The Normalien was chiefly interested in the transformations of matter, and was practising in order to become capable of assisting in experiments; difficulties only stimulated him. At the chemistry class that he attended, the process of obtaining phosphorus was merely explained, on account of the length of time necessary to obtain this elementary substance; Pasteur, with his patience and desire for proven knowledge, was not satisfied. He therefore bought some bones, burnt them, reduced them to a very fine ash, treated this ash with sulphuric acid, and carefully brought the process to its close. What a triumph it seemed to him when he had in his possession sixty grammes of phosphorus, extracted from bones, which he could put into a phial labelled “phosphorus.” This was his first scientific joy.

Whilst his comrades ironically (but with some discernment) called him a “laboratory pillar,” some of them, more intent upon their examinations, were getting ahead of him.—M. Darboux, the present “doyen” of the Faculty[12] of Science, finds in the Sorbonne registers that Pasteur was placed 7th at the licence examination; two other students having obtained equal marks with him, the jury (Balard, Dumas and Delafosse), mentioned his name after theirs.

Those who care for archives would find in the Journal Général de l’Instruction Publique of September 17, 1846, a report of the agrégation[13] competition (physical science). Out of fourteen candidates only four passed and Pasteur was the third. His lessons on physics and chemistry caused the jury to say, “He will make an excellent professor.”

Many Normaliens of that time fancied themselves called to a destiny infinitely superior to his. Some of them, in later times, used to complacently allude to this momentary superiority when speaking to their pupils. Of all Pasteur’s acquaintances Chappuis was the only one who divined the future. “You will see what Pasteur will be,” he used to say, with an assurance generally attributed to friendly partiality. Chappuis—Pasteur’s confidant—was well aware of his friend’s powers of concentration.

Balard also realised this; he had the happy idea of taking the young agrégé into his laboratory, and intervened vehemently when the Minister of Public Instruction desired—a few months later—that Pasteur should teach physics in the Tournon Lycée. It would be rank folly, Balard declared, to send 500 kilometres away from Paris a youth who only asked for the modest title of curator, and had no ambition but to work from morning till night, preparing for his doctor’s degree. There would be time to send him away later on. It was impossible to resist this torrent of words founded on solid sense. Balard prevailed.

Pasteur was profoundly grateful to him for preserving him from exile to the little town in Ardèche; and, as he added to his Franc-Comtois patience and reflective mind a childlike heart and deep enthusiasm, he was delighted to remain with a master like Balard, who had become celebrated, at the age of twenty-four, as the discoverer of bromin.

At the end of 1846, a newcomer entered Balard’s laboratory, a strange delicate-looking man, whose ardent eyes were at the same time proud and yet anxious. This man, a scientist and a poet, was a professor of the Bordeaux Faculty, named Auguste Laurent. Perhaps he had had some friction with his Bordeaux chiefs, possibly he merely wished for a change; at all events, he now desired to live in Paris. Laurent was already known in the scientific world, and had recently been made a correspondent of the Académie des Sciences. He had foreseen and confirmed the theory of substitutions, formulated by Dumas as early as 1834 before the Académie. Dumas had expressed himself thus: “Chlorine possesses the singular power of seizing upon the hydrogen in certain substances, and of taking its place atom by atom.”

This theory of substitutions was—according to a simple and vivid comparison of Pasteur’s—a way of looking upon chemical bodies as upon “molecular edifices, in which one element could be replaced by another without disturbing the structure of the edifice; as if one were to replace, one by one, every stone of a monument by a new stone.” Original researches, new and bold ideas, appealed to Pasteur. But his cautious mind prevented his boldness from leading him into errors, surprises or hasty conclusions. “That is possible,” he would say, “but we must look more deeply into the subject.”

When asked by Laurent to assist him with some experiments upon certain theories, Pasteur was delighted at this suggested collaboration, and wrote to his friend Chappuis: “Even if the work should lead to no results worth publishing, it will be most useful to me to do practical work for several months with such an experienced chemist.”

It was partly due to Laurent, that Pasteur entered more deeply into the train of thought which was to lead him to grapple with Mitscherlich’s problem. “One day” (this is a manuscript note of Pasteur’s) “one day it happened that M. Laurent—studying, if I mistake not, some tungstate of soda, perfectly crystallized and prepared from the directions of another chemist, whose results he was verifying—showed me through the microscope that this salt, apparently very pure, was evidently a mixture of three distinct kinds of crystals, easily recognizable with a little experience of crystalline forms. The lessons of our modest and excellent professor of mineralogy, M. Delafosse, had long since made me love crystallography; so, in order to acquire the habit of using the goniometer, I began to carefully study the formations of a very fine series of combinations, all very easily crystallized, tartaric acid and the tartrates.” He appreciated any favourable influence on his work; we find in the same note: “Another motive urged me to prefer the study of those particular forms. M. de la Provostaye had just published an almost complete work concerning them; this allowed me to compare as I went along my own observations with those, always so precise, of that clever scientist.”