The year passes, the time of the examination arrives, and Pasteur is received as fourth on the list. Thus at last, in the month of October 1843, he finds himself in that École Normale in which he was destined to take so great a place. Pasteur's taste for chemistry had become a passion which he could now satisfy to his heart's content. Chemistry was at this time taught at the Sorbonne by M. Dumas and at the École Normale by M. Balard. The pupils of the École attended both courses of lectures. Different as were the two professors, both of them exercised great influence on their pupils. M. Dumas, with his serene gravity and his profound respect for his auditory, never allowed the smallest incorrectness to slip into his exposition. M. Balard, with a vivacity quite juvenile, with the excitement of a southerner in the tribune, did not always give his words time to follow his thoughts. It was he who once, showing a little potash to his audience, exclaimed with a fervour which has become celebrated, 'Potash, which--potash, then--potash, in short, which I now present to you.' The general principles which M. Dumas in his teaching delighted to develop, the multitude of facts which M. Balard unfolded to his pupils, all answered to the needs of Pasteur's mind. If he loved the vaster horizons of science, he was also possessed by the anxious desire for exactitude, and for the perpetual control of experiment. Each of the lectures of the École Normale and of the Sorbonne excited in him a profound enthusiasm. One day M. Dumas, while illustrating the solidification of carbonic acid, begged for the loan of a handkerchief to receive the carbonic acid snow. Pasteur rushed forward, and, presenting his handkerchief, received the snow. He returned triumphant, and running forthwith to the École Normale, repeated the principal experiments which the illustrious chemist had just exhibited to his audience. He preserved religiously the handkerchief which had been touched by M. Dumas. Pasteur usually spent his Sundays with M. Barruel, the assistant of M. Dumas. He thought of nothing but experiments. For a long time in one of the laboratories of the École Normale was exhibited a basin--perhaps it is still shown--containing sixty grammes of phosphorus obtained from bones bought at the butcher's by Pasteur. These he had calcined, submitted to the processes known to chemists, and finally reduced, after a whole day's heating, from four in the morning to nine in the evening, to the said sixty grammes. It was the first time that the long manipulations required in the preparation of this simple substance were attempted at the École Normale.