His usual examination fortune attended him upon this occasion. His classmates, who were wise in their generation, merely cramming for the test, came through with flying colors while his name appeared near the bottom of the list. And in the state examination which followed, his name was put next to the last. Apparently his not being rejected was due solely to the excellence which he displayed in the practical phase of the examination wherein the candidates went through the form of actually teaching a class. The lessons in physics and chemistry given by Pasteur caused the jury to declare "he will become an excellent teacher."
He was appointed laboratory assistant to Laurent, the first to formulate an hypothesis of the substitution of hydrogen in hydrocarbons. This theory was elaborated, and enunciated in its final form, by Dumas in 183-1. At this time, Laurent was working on sodium tungstate. One day he showed his assistant, under the microscope, some crystals of this salt supposedly pure but which manifested three distinct forms of crystallization. Pasteur began at once to learn how to use the goniometer. In order to master its technique, he made elaborate measurements on all easily crystallizable tartrates, thus revealing the fact that his curiosity concerning the two known tartaric acids had remained lively throughout the preceding two years.
In the meantime he was working toward the doctorate, which he achieved August 23, 1847, on the strength of two small papers, the one entitled "Researches on the Saturation Capacities of Arsenious Acid: A Study of the Arsenites of Soda, Potassa and Ammonia," and the other "A Study of the Phenomena Relative to the Polarization of Liquids."
He himself said of these papers, "They are elementary, and little more than programs for future work." Again he attained but poor ranking.
He now desired to study in Germany; but poverty frustrated his plans. On March 20, 1848, he read before the Académie des Sciences a part of a paper on dimorphism which was little more than a catalogue of all known substances crystallizing in two forms. Of itself, one might say that it was almost valueless. But to the student of Pasteur's life it was a proof that his work on the tartrates was still being prosecuted; and it afforded an index pointing out the tenacious purpose and the resolute will of the man.
After a flash of republican ardor in 1848, in which he not only volunteered service but also contributed to the cause all his savings, 150 francs, he returned to his crystals, and soon had the fortune to discover hemihedrism in the tartrates, a fact that had escaped the scrutiny of Mitscherlich and of Provostaye.
So far as his investigations showed, all crystals of tartaric acid had