Davy, on the other hand, was surrounded from childhood by scenes of great natural beauty and variety, by contact with which he was incited to eager desire for knowledge, while at the same time his emotions remained fresh and sensitive to outward impressions. Entering on the study of natural science when there was a pause in the march of discovery, but a pause presageful of fresh advances, he found outward circumstances singularly favourable to his success; seizing these favourable circumstances he made rapid advances. Like Lavoisier, he began his work by proving that there is no such thing in Nature as transmutation, in the alchemical meaning of the term; as Lavoisier had proved that water is not changed into earth, so did Davy prove that acid and alkali are not produced by the action of the electric current on pure water. We have shortly traced the development of the electro-chemical theory which Davy raised on the basis of experiment; we have seen how facts obliged him to doubt the accepted view of the composition of hydrochloric acid and chlorine, and how by the work he did on these subjects chemists have been finally convinced that an element is not a substance which _cannot be_, but a substance which _has not been_ decomposed, and how from this work has also arisen the modern theory of acids, bases and salts. We found that, by the labours of the great Swede J. J. Berzelius, the Daltonian theory was confirmed by a vast series of accurate analyses, and, in conjunction with a modification of the electro-chemical theory of Davy, was made the basis of a system of classification which endeavoured to include all chemical substances within its scope. The atom was the starting-point of the Berzelian system, but that chemist viewed the atom as a dual structure the parts of which held together by reason of their opposite electrical polarities. Berzelius, we saw, greatly improved the methods whereby atomic weights could be determined, and he recognized the importance of physical generalizations as aids in finding the atomic weights of chemical substances. But Berzelius came to believe too implicitly in his own view of Nature's working; his theory became too imperious. Chemists found it easier to accept than to doubt an interpretation of facts which was in great part undeniably true, and which formed a central luminous conception, shedding light on the whole mass of details which, without it, seemed confused and without meaning. If the dualistic stronghold was to be carried, the attack should be impetuous, and should be led by men, not only of valour, but also of discretion. We found that two champions appeared, and that, aided by others who were scarcely inferior soldiers to themselves, they made the attack, and made it with success.