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.”

Pasteur and Laurent’s work in common was interrupted. Laurent was appointed as Dumas’ assistant at the Sorbonne. Pasteur did not dwell upon his own disappointment, but rejoiced to see honour bestowed upon a man whom he thought worthy of the first rank. Some judges have thought that Laurent, in his introductory lesson, was too eager to expound his own ideas; but is not every believer an apostle? When a mind is full of ideas, it naturally overflows. It is probable that Pasteur in Laurent’s place would have kept his part as an assistant more in the background. He did not give vent to the slightest criticism, but wrote to Chappuis. “Laurent’s lectures are as bold as his writings, and his lessons are making a great sensation amongst chemists.” Whether one of criticism or of approbation, this sensation was a living element of success. In order to answer some insinuations concerning Laurent’s ambition and constant thirst for change, Pasteur proclaimed in his thesis on chemistry how much he had been “enlightened by the kindly advice of a man so distinguished, both by his talent and by his character.”

This essay was entitled “Researches into the saturation capacity of arsenious acid. A study of the arsenites of potash, soda and ammonia.” This, to Pasteur’s mind, was but schoolboy work. He had not yet, he said, enough practice and experience in laboratory work. “In physics,” he wrote to Chappuis, “I shall only present a programme of some researches that I mean to undertake next year, and that I merely indicate in my essay.”

This essay on physics was a “Study of phenomena relative to the rotatory polarization of liquids.” In it he rendered full homage to Biot, pointing out the importance of a branch of science too much neglected by chemists; he added that it was most useful, in order to throw light upon certain difficult chemical problems, to obtain the assistance of crystallography and physics. “Such assistance is especially needed in the present state of science.”

These two essays, dedicated to his father and mother, were read on August 23, 1847. He only obtained one white ball and two red ones for each. “We cannot judge of your essays,” wrote his father, in the name of the whole family, “but our satisfaction is no less great. As to a doctor’s degree, I was far from hoping as much; all my ambition was satisfied with the agrÉgation.” Such was not the case with his son. “Onwards” was his motto, not from a desire for a diploma, but from an insatiable thirst for knowledge.

After spending a few days with his family and friends, he wanted to go to Germany with Chappuis to study German from morning till night. The prospect of such industrious holidays enchanted him. But he had forgotten a student’s debt. “I cannot carry out my project,” he sadly wrote, on September 3, 1847; “I am more than ruined by the cost of printing my thesis.”

On his return to Paris he shut himself up in the laboratory. “I am extremely happy. I shall soon publish a paper on crystallography.” His father writes (December 25, 1847): “We received your letter yesterday; it is absolutely satisfactory, but it could not be otherwise coming from you; you have long, indeed ever, been all satisfaction to me.” And in response to his son’s intentions of accomplishing various tasks, fully understanding that nothing will stop him: “You are doing right to make for your goal; it was only out of excessive affection that I have often written in another sense. I only feared that you might succumb to your work; so many noble youths have sacrificed their health to the love of science. Knowing you as I do, this was my only anxiety.”

After being reproved for excessive work, Louis was reprimanded for too much affection (January 1, 1848). “The presents you sent have just arrived; I shall leave it to your sisters to write their thanks. For my part, I should prefer a thousand times that this money should still be in your purse, and thence to a good restaurant, spent in some good meals that you might have enjoyed with your friends. There are not many parents, my dearest boy, who have to write such things to their son; my satisfaction in you is indeed deeper than I can express.” At the end of this same letter, the mother adds in her turn: “My darling boy, I wish you a happy new year. Take great care of your health.... Think what a worry it is to me that I cannot be with you to look after you. Sometimes I try to console myself for your absence by thinking how fortunate I am in having a child able to raise himself to such a position as yours is—such a happy position, as it seems to be from your last letter but one.” And in a strange sentence, where it would seem that a presentiment of her approaching death made worldly things appear at their true value: “Whatever happens to you, do not grieve; nothing in life is more than a chimera. Farewell, my son.”

On March 20, 1848, Pasteur read to the AcadÉmie des Sciences a portion of his treatise on “Researches on Dimorphism.” There are some substances which crystallize in two different ways. Sulphur, for instance, gives quite dissimilar crystals according to whether it is melted in a crucible or dissolved in sulphide of carbon. Those substances are called dimorphous. Pasteur, kindly aided by the learned M. Delafosse (with his usual gratefulness he mentions this in the very first pages) had made out a list—as complete as possible—of all dimorphous substances. When M. Romanet, of Arbois College, received this paper he was quite overwhelmed. “It is much too stiff for you,” he said with an infectious modesty to Vercel, CharriÈre, and Coulon, Pasteur’s former comrades. Perhaps the head master desired to palliate his own incompetence in the eyes of coming generations, for on the title page of the copy of Pasteur’s booklet still to be found in the Arbois library, he wrote this remark, which he signed with his initial R.:—“Dimorphisme; this word is not even to be found in the Dictionnaire de l’AcadÉmie”!! The approbation of several members of the AcadÉmie des Sciences compensated for the somewhat summary judgment of M. Romanet, whose good wishes continued to follow the rapid course of his old pupil.

After this very special study, dated at the beginning of 1848, one might imagine the graduate-curator closing his ears to all outside rumours and little concerned with political agitation, but that would be doing him an injustice. Those who witnessed the Revolution of 1848 remember how during the early days France was exalted with the purest patriotism. Pasteur had visions of a generous and fraternal Republic; the words drapeau and patrie moved him to the bottom of his soul. Lamartine[14] as a politician inspired him with an enthusiastic confidence; he delighted in the sight of a poet leader of men. Many others shared the same illusions. France, as Louis Veuillot has it, made the mistake of choosing her band-master as colonel of the regiment. Enrolled with his fellow students, Pasteur wrote thus to his parents: “I am writing from the Orleans Railway, where as a garde national[15] I am stationed. I am glad that I was in Paris during the February days[16] and that I am here still; I should be sorry to leave Paris just now. It is a great and a sublime doctrine which is now being unfolded before our eyes ... and if it were necessary I should heartily fight for the holy cause of the Republic.” “What a transformation of our whole being!” has written one who was then a candidate to the Ecole Normale, already noted by his masters for his good sense, Francisque Sarcey. “How those magical words of liberty and fraternity, this renewal of the Republic, born in the sunshine of our twentieth year, filled our hearts with unknown and absolutely delicious sensations! With what a gallant joy we embraced the sweet and superb image of a people of free men and brethren! The whole nation was moved as we were; like us, it had drunk of the intoxicating cup. The honey of eloquence flowed unceasingly from the lips of a great poet, and France believed, in childlike faith, that his word was efficacious to destroy abuses, cure evils and soothe sorrows.”

One day when Pasteur was crossing the Place du PanthÉon, he saw a gathering crowd around a wooden erection, decorated with the words: Autel de la Patrie. A neighbour told him that pecuniary offerings might be laid upon this altar. Pasteur goes back to the Ecole Normale, empties a drawer of all his savings, and returns to deposit it in thankful hands.

“You say,” wrote his father on April 28, 1848, “that you have offered to France all your savings, amounting to 150 francs. You have probably kept a receipt of the office where this payment was made, with mention of the date and place?” And considering that this action should be made known, he advises him to publish it in the journal Le National or La RÉforme in the following terms, “Gift to the Patrie: 150 francs, by the son of an old soldier of the Empire, Louis Pasteur of the Ecole Normale.” He wrote in the same letter, “You should raise a subscription in your school in favour of the poor Polish exiles who have done so much for us; it would be a good deed.”

After those days of national exaltation, Pasteur returned to his crystals. He studied tartrates under the influence of certain ideas that he himself liked to expound. Objects considered merely from the point of view of form, may be divided into two great categories. First, those objects which, placed before a mirror, give an image which can be superposed to them: these have a symmetrical plan; secondly, those which have an image which cannot be superposed to them: they are dissymmetrical. A chair, for instance, is symmetrical, or a straight flight of steps. But a spiral staircase is not symmetrical, its own image cannot be laid over it. If it turns to the right, its image turns to the left. In the same way the right hand cannot be superposed to the left hand, a righthand glove does not fit a left hand, and a right hand seen in a mirror gives the image of a left hand.

Pasteur noticed that the crystals of tartaric acid and the tartrates had little faces, which had escaped even the profound observation of Mitscherlich and La Provostaye. These faces, which only existed on one half of the edges or similar angles, constituted what is called a hemihedral form. When the crystal was placed before a glass the image that appeared could not be superposed to the crystal; the comparison of the two hands was applicable to it. Pasteur thought that this aspect of the crystal might be an index of what existed within the molecules, dissymmetry of form corresponding with molecular dissymmetry. Mitscherlich had not perceived that his tartrate presented these little faces, this dissymmetry, whilst his paratartrate was without them, was in fact not hemihedral. Therefore, reasoned Pasteur, the deviation to the right of the plane of polarization produced by tartrate and the optical neutrality of paratartrates would be explained by a structural law. The first part of these conclusions was confirmed; all the crystals of tartrate proved to be hemihedral. But when Pasteur came to examine the crystals of paratartrate, hoping to find none of them hemihedral, he experienced a keen disappointment. The paratartrate also was hemihedral, but the faces of some of the crystals were inclined to the right, and those of others to the left. It then occurred to Pasteur to take up these crystals one by one and sort them carefully, putting on one side those which turned to the left, and on the other those which turned to the right. He thought that by observing their respective solutions in the polarizing apparatus, the two contrary hemihedral forms would give two contrary deviations; and then, by mixing together an equal number of each kind, as no doubt Mitscherlich had done, the resulting solution would have no action upon light, the two equal and directly opposite deviations exactly neutralizing each other.

With anxious and beating heart he proceeded to this experiment with the polarizing apparatus and exclaimed, “I have it!” His excitement was such that he could not look at the apparatus again; he rushed out of the laboratory, not unlike Archimedes. He met a curator in the passage, embraced him as he would have embraced Chappuis, and dragged him out with him into the Luxembourg garden to explain his discovery. Many confidences have been whispered under the shade of the tall trees of those avenues, but never was there greater or more exuberant joy on a young man’s lips. He foresaw all the consequences of his discovery. The hitherto incomprehensible constitution of paratartaric or racemic acid was explained; he differentiated it into righthand tartaric acid, similar in every way to the natural tartaric acid of grapes, and lefthand tartaric acid. These two distinct acids possess equal and opposite rotatory powers which neutralize each other when these two substances, reduced to an aqueous solution, combine spontaneously in equal quantities.

“How often,” he wrote to Chappuis (May 5), whom he longed to have with him, “how often have I regretted that we did not both take up the same study, that of physical science. We who so often talked of the future, we did not understand. What splendid work we could have undertaken and would be undertaking now; and what could we not have done united by the same ideas, the same love of science, the same ambition! I would we were twenty and with the three years of the Ecole before us!” Always fancying that he could have done more, he often had such retrospective regrets. He was impatient to begin new researches, when a sad blow fell upon him—his mother died almost suddenly of apoplexy. “She succumbed in a few hours,” he wrote to Chappuis on May 28, “and when I reached home she had already left us. I have asked for a holiday.” He could no longer work; he remained steeped in tears and buried in his sorrow. For weeks his intellectual life was suspended.

In Paris, in the scientific world perhaps even more than in any other, everything gets known, repeated, discussed. Pasteur’s researches were becoming a subject of conversation. Balard, with his strident voice, spoke of them in the library at the Institute, which is a sort of drawing-room for talkative old Academicians. J. B. Dumas listened gravely; Biot, old Biot, then seventy-four years old, questioned the story with some scepticism. “Are you quite sure?” he would ask, his head a little on one side, his words slow and slightly ironical. He could hardly believe, on first hearing Balard, that a new doctor, fresh from the Ecole Normale, should have overcome a difficulty which had proved too much for Mitscherlich. He did not care for long conversations with Balard, and as the latter continued to extol Pasteur, Biot said, “I should like to investigate that young man’s results.”

Besides Pasteur’s deference for all those whom he looked upon as his teachers, he also felt a sort of general gratitude for their services to Science. Partly from an infinite respect and partly from an ardent desire to convince the old scientist, he wrote on his return to Paris to Biot, whom he did not know personally, asking him for an interview. Biot answered: “I shall be pleased to verify your results if you will communicate them confidentially to me. Please believe in the feelings of interest inspired in me by all young men who work with accuracy and perseverance.”

An appointment was made at the CollÈge de France,[17] where Biot lived. Every detail of that interview remained for ever fixed in Pasteur’s memory. Biot began by fetching some paratartaric acid. “I have most carefully studied it,” he said to Pasteur; “it is absolutely neutral in the presence of polarized light.” Some distrust was visible in his gestures and audible in his voice. “I shall bring you everything that is necessary,” continued the old man, fetching doses of soda and ammonia. He wanted the salt prepared before his eyes.

After pouring the liquid into a crystallizer, Biot took it into a corner of his room to be quite sure that no one would touch it. “I shall let you know when you are to come back,” he said to Pasteur when taking leave of him. Forty-eight hours later some crystals, very small at first, began to form; when there was a sufficient number of them, Pasteur was recalled. Still in Biot’s presence, Pasteur withdrew, one by one, the finest crystals and wiped off the mother-liquor adhering to them. He then pointed out to Biot the opposition of their hemihedral character, and divided them into two groups—left and right.

“So you affirm,” said Biot, “that your righthand crystals will deviate to the right the plane of polarization, and your lefthand ones will deviate it to the left?”

“Yes,” said Pasteur.

“Well, let me do the rest.”

Biot himself prepared the solutions, and then sent again for Pasteur. Biot first placed in the apparatus the solution which should deviate to the left. Having satisfied himself that this deviation actually took place, he took Pasteur’s arm and said to him these words, often deservedly quoted: “My dear boy, I have loved Science so much during my life, that this touches my very heart.”

“It was indeed evident,” said Pasteur himself in recalling this interview, “that the strongest light had then been thrown on the cause of the phenomenon of rotatory polarization and hemihedral crystals; a new class of isomeric substances was discovered; the unexpected and until then unexampled constitution of the racemic or paratartaric acid was revealed; in one word a great and unforeseen road was opened to science.”

Biot now constituted himself the sponsor in scientific matters of his new young friend, and undertook to report upon Pasteur’s paper entitled: “Researches on the relations which may exist between crystalline form, chemical composition, and the direction of rotatory power”—destined for the AcadÉmie des Sciences.

Biot did full justice to Pasteur; he even rendered him homage, and—not only in his own name but also in that of his three colleagues, Regnault, Balard, and Dumas—he suggested that the AcadÉmie should declare its highest approbation of Pasteur’s treatise.

Pasteur did not conceive greater happiness than his laboratory life, and yet the laboratories of that time were very unlike what they are nowadays, as we should see if the laboratories of the CollÈge de France, of the Sorbonne, of the Ecole Normale had been preserved. They were all that Paris could offer Europe, and Europe certainly had no cause to covet them. Nowadays the most humble college, in the smallest provincial town, would not accept such dens as the State offered (when it offered them any) to the greatest French scientists. Claude Bernard, Magendie’s curator, worked at the CollÈge de France in a regular cellar. Wurtz only had a lumber-room in the attics of the Dupuytren Museum. Henri Sainte Claire Deville, before he became head of the BesanÇon Faculty, had not even as much; he was relegated to one of the most miserable corners of the Rue Lafarge. J. B. Dumas did not care to occupy the unhealthy room reserved for him at the Sorbonne; his father-in-law, Alexandre Brongniart, having given him a small house in the Rue Cuvier, opposite the Jardin des Plantes, he had had it transformed into a laboratory and was keeping it up at his own expense. He was therefore comfortably situated, but he was exceptionally fortunate. Every scientist who had no private means to draw upon had to choose between the miserable cellars and equally miserable garrets which were all that the State could offer. And yet it was more tempting than a Professor’s chair in a College or even in a Faculty, for there one could not give oneself up entirely to one’s work.

Nothing would have seemed more natural than to leave Pasteur to his experiments. But his appointment to some definite post could no longer be deferred, in spite of Balard’s tumultuous activity. The end of the summer vacation was near, there was a vacancy: Pasteur was made a Professor of Physics at the Dijon LycÉe. The Minister of Public Instruction consented to allow him to postpone his departure until the beginning of November, in order to let him finish some work begun under the eye of Biot, who thought and dreamt of nothing but these new investigations. During thirty years Biot had studied the phenomena of rotatory polarization. He had called the attention of chemists to these phenomena, but his call had been unheeded. Continuing his solitary labour, he had—in experimenting on cases both simple and complex—studied this molecular rotatory power, without suspecting that this power bore a definite relation to the hemihedral form of some crystals. And now that the old man was a witness of a triumphant sequel to his own researches, now that he had the joy of seeing a young man with a thoughtful mind and an enthusiastic heart working with him, now that the hope of this daily collaboration shed a last ray on the close of his life, Pasteur’s departure for Dijon came as a real blow. “If at least,” he said, “they were sending you to a Faculty!” He turned his wrath on to the Government officials. “They don’t seem to realize that such labours stand above everything else! If they only knew it, two or three such treatises might bring a man straight to the Institut!”

Nevertheless Pasteur had to go. M. Pouillet gave him a letter for a former Polytechnician,[18] now a civil engineer at Dijon, a M. Parandier, in which he wrote—

“M. Pasteur is a most distinguished young chemist. He has just completed some very remarkable work, and I hope it will not be long before he is sent to a first-class Faculty. I need add nothing else about him; I know no more honest, industrious, or capable young man. Help him as much as you can at Dijon; you will not regret it.”

Those first weeks away from his masters and from his beloved pursuits seemed very hard to Pasteur. But he was anxious to prove himself a good teacher. This duty appeared to him to be a noble ideal, and to involve a wide responsibility. He felt none of the self satisfaction which is sometimes a source of strength to some minds conscious of their superiority to others. He did not even do himself the justice of feeling that he was absolutely sure of his subject. He wrote to Chappuis (November 20, 1848): “I find that preparing my lessons takes up a great deal of time. It is only when I have prepared a lesson very carefully that I succeed in making it very clear and capable of compelling attention. If I neglect it at all I lecture badly and become unintelligible.”

He had both first and second year pupils; these two classes took up all his time and all his strength. He liked the second class; it was not a very large one. “They all work,” Pasteur wrote, “some very intelligently.” As to the first year class, what could he do with eighty pupils? The good ones were kept back by the bad. “Don’t you think,” he wrote, “that it is a mistake not to limit classes to fifty boys at the most? It is with great difficulty that I can secure the attention of all towards the end of the lesson. I have only found one means, which is to multiply experiments at the last moment.”

Whilst he was eagerly and conscientiously giving himself up to his new functions—not without some bitterness, for he really was entitled to an appointment in a Faculty, and he could not pursue his favourite studies—his masters were agitating on his behalf. Balard was clamouring to have him as an assistant at the Ecole Normale. Biot was appealing to Baron Thenard. This scientist was then Chairman of the Grand Council of the UniversitÉ.[19] He had been a pupil of Vauquelin, a friend of Laplace, and a collaborator of Gay-Lussac; he had lectured during thirty years at the Sorbonne, at the CollÈge de France, and at the Ecole Polytechnique; he could truthfully boast that he had had 40,000 pupils. He was, like J. B. Dumas, a born professor. But, whilst Dumas was always self possessed and dignified in his demeanour, his very smile serious, Thenard, a native of Burgundy, threw his whole personality into his work, a broad smile on his beaming face.

He was now (1848) seventy years old, and the memory of his teaching, the services rendered to industry by his discoveries, the Éclat of his name and titles contrasted with his humble origin, all combined to render him more than a Chancellor of the University; he was in fact a sort of Field Marshal of science, and all powerful. Three years previously he had much scandalized certain red-tape officials by choosing three very young men—Puiseux, Delesse, and H. Sainte Claire Deville—as professors for the new Faculty of Science at BesanÇon. He had accentuated this authoritative measure by making Sainte Claire Deville Dean of the Faculty. In the unknown professor of twenty-six, he had divined the future celebrated scientist.

At the end of the year 1848 Pasteur solicited the place of assistant to M. Delesse, who was taking a long leave of absence. This would have brought him near Arbois, besides placing him in a Faculty. He asked for nothing more. Thenard, who had Biot’s report in his hands, undertook to transmit to the Minister this modest and natural request. He was opposed by an unexpected argument—the presentation of assistantships belonged to each Faculty. This custom was unknown to Pasteur. Thenard was unable to overcome this routine formality. Pasteur thought that the unanimous opinion of Thenard, Biot, and Pouillet ought to have prevailed. “I can practically do nothing here,” he wrote on the sixth of December, thinking of his interrupted studies. “If I cannot go to BesanÇon, I shall go back to Paris as a curator.”

His father, to whom he paid a visit for the new year, persuaded him to look upon things more calmly, telling him that wisdom repudiated too much hurry. Louis deferred to his father’s opinion to the extent of writing, on January 2, 1849, to the Minister of Public Instruction, begging him to overlook his request. However, the members of the Institute who had taken up his cause did not intend to be thwarted by minor difficulties. Pasteur’s letter was hardly posted when he received an assistantship, not at the BesanÇon Faculty but at Strasburg, to take the place of M. Persoz, Professor of Chemistry, who was desirous of going to Paris.

Pasteur, on his arrival at Strasburg (January 15) was welcomed by the Professor of Physics, his old school friend, the Franc-Comtois Bertin. “First of all, you are coming to live with me,” said Bertin gleefully. “You could not do better; it is a stone’s throw from the FacultÉ.” By living with Bertin, Pasteur acquired a companion endowed with a rare combination of qualities—a quick wit and an affectionate heart. Bertin was too shrewd to be duped, and a malicious twinkle often lit up his kindly expression; with one apparently careless word, he would hit the weak point of the most self satisfied. He loved those who were simple and true, hence his affection for Pasteur. His smiling philosophy contrasted with Pasteur’s robust faith and ardent impetuosity. Pasteur admired, but did not often imitate, the peaceful manner with which Bertin, affirming that a disappointment often proved to be a blessing in disguise, accepted things as they came. In order to prove that this was no paradox, Bertin used to tell what had happened to him in 1839, when he was mathematical preparation master at the College of Luxeuil. He was entitled to 200 francs a month, but payment was refused him. This injustice did not cause him to recriminate, but he quietly tendered his resignation. He went in for the Ecole Normale examination, entered the school at the head of the list, and subsequently became Professor of Physics at the Strasburg Faculty. “If it had not been for my former disappointment, I should still be at Luxeuil.” He was now perfectly satisfied, thinking that nothing could be better than to be a Professor in a Faculty; but this absence of any sort of ambition did not prevent him from giving his teaching the most scrupulous attention. He prepared his lessons with extreme care, endeavouring to render them absolutely clear. He took great personal interest in his pupils, and often helped them with his advice in the interval between class hours. This excellent man’s whole life was spent in working for others, and to be useful was ever to him the greatest satisfaction.

Perhaps Pasteur was stimulated by Bertin’s example to give excessive importance to minor matters in his first lessons. He writes: “I gave too much thought to the style of my two first lectures, and they were anything but good; but I think the subsequent ones were more satisfactory, and I feel I am improving.” His lectures were well attended, for the numerous industries of Alsace gave to chemistry quite a place by itself.

Everything pleased him in Strasburg save its distance from Arbois. He who could concentrate his thoughts for weeks, for months even, on one subject, who could become as it were a prisoner of his studies, had withal an imperious longing for family life. His rooms in Bertin’s house suited him all the better that they were large enough for him to entertain one of his relations. His father wrote in one of his letters: “You say that you will not marry for a long time, that you will ask one of your sisters to live with you. I could wish it for you and for them, for neither of them wishes for a greater happiness. Both desire nothing better than to look after your comfort; you are absolutely everything to them. One may meet with sisters as good as they are, but certainly with none better.”

Louis Pasteur’s circle of dear ones was presently enlarged by his intimacy with another family. The new Rector of the Academy of Strasburg, M. Laurent, had arrived in October. He was no relation to the chemist of the same name, and the place he was about to take in Pasteur’s life was much greater than that held by Auguste Laurent at the time when they were working together in Balard’s laboratory.

After having begun, in 1812, as preparation master in the then Imperial College of Louis le Grand, M. Laurent had become, in 1826, head master of the College of Riom. He found at Riom more tutors than pupils; there were only three boys in the school! Thanks to M. Laurent, those three soon became one hundred and thirty-four. From Riom he was sent to GuÉret, then to Saintes, to save a college in imminent danger of disappearing; there were struggles between the former head master and the Mayor, the town refused the subsidies, all was confusion. Peace immediately followed his arrival. “Those who have known him,” wrote M. Pierron in the Revue de l’Instruction Publique, “will not be surprised at such miracles coming from a man so intelligent and so active, so clever, amiable, and warm-hearted.” Wherever he was afterwards sent, at Orleans, AngoulÊme, Douai, Toulouse, Cahors, he worked the same charm, born of kindness. At Strasburg, he had made of the AcadÉmie a home where all the Faculty found a simple and cordial welcome. Madame Laurent was a modest woman who tried to efface herself, but whose exquisite qualities of heart and mind could not remain hidden. The eldest of her daughters was married to M. Zevort, whose name became doubly dear to the UniversitÉ. The two younger ones, brought up in habits of industry and unselfishness which seemed natural to them, brightened the home by their youthful gaiety.

When Pasteur on his arrival called on this family, he had the feeling that happiness lay there. He had seen at Arbois how, through the daily difficulties of manual labour, his parents looked at life from an exalted point of view, appreciating it from that standard of moral perfection which gives dignity and grandeur to the humblest existence. In this family—of a higher social position than his own—he again found the same high ideal, and, with great superiority of education, the same simple-mindedness. When Pasteur entered for the first time the Laurent family circle, he immediately felt the delightful impression of being in a thoroughly congenial atmosphere; a communion of thoughts and feelings seemed established after the first words, the first looks exchanged between him and his hosts.

In the evening, at the restaurant where most of the younger professors dined, he heard others speak of the kindliness and strict justice of the Rector; and everyone expressed respect for his wonderfully united family.

At one of M. Laurent’s quiet evening “at homes,” Bertin was saying of Pasteur, “You do not often meet with such a hard worker; no attraction ever can take him away from his work.” The attraction now came, however, and it was such a powerful one that, on February 10, only a fortnight after his arrival, Pasteur addressed to M. Laurent the following official letter:—

A definite answer was adjourned for a few weeks. Pasteur, in a letter to Madame Laurent, wrote, “I am afraid that Mlle. Marie may be influenced by early impressions, unfavourable to me. There is nothing in me to attract a young girl’s fancy. But my recollections tell me that those who have known me very well have loved me very much.”

Of these letters, religiously preserved, fragments like the following have also been obtained. “All that I beg of you, Mademoiselle (he had now been authorised to address himself directly to her) is that you will not judge me too hastily, and therefore misjudge me. Time will show you that below my cold, shy and unpleasing exterior, there is a heart full of affection for you!” In another letter, evidently remorseful at forsaking the laboratory, he says, “I, who did so love my crystals!”

He loved them still, as is proved by an answer from Biot to a proposal of Pasteur’s. In order to spare the old man’s failing sight, Pasteur had the ingenious idea of cutting out of pieces of cork, with exquisite skill, some models of crystalline types greatly enlarged. He had tinted the edges and faces, and nothing was easier than to recognize their hemihedral character. “I accept with great pleasure,” wrote Biot on April 7, “the offer you make me of sending me a small quantity of your two acids, with models of their crystalline types.” He meant the righthand tartaric acid and the lefthand tartaric acid, which Pasteur—not to pronounce too hastily on their identity with ordinary tartaric acid—then called dextroracemic and lÆvoracemic.

Pasteur wished to go further; he was now beginning to study the crystallizations of formate of strontian. Comparing them with those of the paratartrates of soda and ammonia, surprised and uneasy at the differences he observed, he once exclaimed, “Ah! formate of strontian, if only I had got you!” to the immense amusement of Bertin, who long afterwards used to repeat this invocation with mock enthusiasm.

Pasteur was about to send these crystals to Biot, but the latter wrote, “Keep them until you have thoroughly investigated them.... You can depend on my wish to serve you in every circumstance when my assistance can be of any use to you, and also on the great interest with which you have inspired me.”

Regnault and Senarmont had been invited by Biot to examine the valuable samples received from Strasburg, the dextroracemic and lÆvoracemic acids. Biot wrote to Pasteur, “We might make up our minds to sacrifice a small portion of the two acids in order to reconstitute the racemic, but we doubt whether we should be capable of discerning it with certainty by those crystals when they are formed. You must show it us yourself, when you come to Paris for the holidays. Whilst arranging my chemical treasures, I came upon a small quantity of racemic acid which I thought I had lost. It would be sufficient for the microscopical experiments that I might eventually have to make. So if the small phial of it that you saw here would be useful to you, let me know, and I will willingly send it. In this, as in everything else, you will always find me most anxious to second you in your labours.”

This period was all happiness. Pasteur’s father and his sister Josephine came to Strasburg. The proposal of marriage was accepted, the father returned to Arbois, Josephine staying behind. She remained to keep house and to share the everyday life of her brother, whom she loved with a mixture of pride, tenderness and solicitude. In her devoted sisterly generosity, she resigned herself to the thought that her happy dream must be of short duration. The wedding was fixed for May 29.

“I believe,” wrote Pasteur to Chappuis, “that I shall be very happy. Every quality I could wish for in a wife I find in her. You will say, ‘He is in love!’ Yes, but I do not think I exaggerate at all, and my sister Josephine quite agrees with me.”