There is said to exist a constant, unappeasable warfare between science and religion. Perhaps it does exist, but surely only in the narrow minds of the lesser lights. In no century has science developed as in the one that has just closed. Faraday the great scientific mind of the beginning of the century, said, at one of his lectures before the Royal Academy of Sciences of England, when the century was scarcely a decade old: "I do not name God here because I am lecturing on experimental science. But the notion of respect for God comes to my mind by ways as sure as those {296} which lead us to physical truth." At the end of the century the monument of a great man of science is a chapel with an altar on which the sacrifice of Him that died for men is commemorated on Pasteur anniversaries. The walls of the chapel are inscribed with the scientific triumphs of the master whose ashes repose here. It is a striking catalogue. Each heading represents a great step forward in science: 1848, Molecular Dissymmetry. 1857, Fermentations. 1862, So-called Spontaneous Generation. 1863, Studies in Wine. 1865, Diseases of Silk Worms. 1871, Studies in Beer. 1877, Virulent Microbic Diseases. 1880, Vaccinating Viruses. 1885, Prophylaxis of Rabies. Apparently these various subjects are widely separated from one another. It might seem that Pasteur was an erratic genius. As a matter of fact, each successive subject follows its predecessor by a rigid logic. Pasteur's life-work can be best studied by a consideration of these various topics and an appreciation of the advance made in each one. Pasteur was first of all and always a chemist! He was interested in chemistry from his early years. In the decade from 1840 to 1850 organic chemistry--or as we prefer to call it now, the chemistry of the carbon compounds--was just opening up. Great discoveries were possible as they were not before or since. Pasteur, with a devotion to experimental work that amounted to a passion, was a pupil at the Ecole Normale, in Paris. Bruited about he heard all the suggestive questions that were insoluble problems even to the great men around him. He was especially interested in the burning {297} question of the day, the internal constitution of molecules and the arrangement of atoms in substances which, though they are composed of exactly the same constituents, exhibit very different physical and chemical qualities. The subject is, almost needless to say, a basic problem in chemistry and remains to our own day the most attractive of scientific mysteries.