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.