I. IN this work are collected and discussed the results of the chemical investigations on the nature of the water of the North Atlantic, made during the Norwegian expeditions of the summers 1876, 1877, and 1878. The contents of the volume are divided into three chapters—I. On the Air in Sea Water; II. On the Carbonic Acid in Sea Water; and III. On the Amount of Salt in the Water of the Norwegian Sea. It is therefore wholly concerned with the chemistry of the water; chemical researches in other directions are promised for a future volume. Although the subject is thus restricted, there is abundant matter of the greatest interest both from a chemical and from a geographical point of view.