In a mere study on Pasteur as a scientific man, the way in which he understood his duties as Dean would only be a secondary detail. It is not so here, the very object of this book being to paint what he was in all the circumstances, all the trials of life. Besides his professional obligations, his kindness in leaving his laboratory, however hard the sacrifice, bears witness to an ever present devotion. For instance, he took his pupils round factories and foundries at Aniche, Denain, Valenciennes, St. Omer. In July, 1856, he organized for the same pupils a tour in Belgium. He took them to visit factories, iron foundries, steel and metal works, questioning the foremen with his insatiable curiosity, pleased to induce in his tall students a desire to learn. All returned from these trips with more pleasure in their work; some with the fiery enthusiasm that Pasteur wished to see. The sentence in his Lille speech, “in the fields of observation, chance only favours the mind which is prepared,” was particularly applicable to him. In the summer of 1856 a Lille manufacturer, M. Bigo, had, like many others that same year, met with great disappointments in the manufacture of beetroot alcohol. He came to the young Dean for advice. The prospect of doing a kindness, of communicating the results of his observations to the numerous hearers who crowded the small theatre of the Faculty, and of closely studying the phenomena of fermentation which preoccupied him to such a degree, caused Pasteur to consent to make some experiments. He spent some time almost daily at the factory. On his return to his laboratory--where he only had a student’s microscope and a most primitive coke-fed stove--he examined the globules in the fermentation juice, he compared filtered with non-filtered beetroot juice, and conceived stimulating hypotheses often to be abandoned in face of a fact in contradiction with them. Above some note made a few days previously, where a suggested hypothesis had not been verified by fact, he would write: “error,” “erroneous,” for he was implacable in his criticism of himself.