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.”