With what difficulty do we extract a drop of perfectly sweet water from this vast pit of brine! Yet the sun draws off, every moment, millions of tons in vaporous exhalations, which, being securely lodged in the clouds, are sent abroad sweetened and refined, without the least brackish tincture or bituminous sediment; sent abroad upon the wings of the winds to distil in dews and rain, to ooze in fountains, to trickle along in rivulets, to roll from the sides of mountains, to flow in copious streams amid burning deserts and populous kingdoms, in order to refresh and fertilise, to beautify and enrich, every soil in every clime. Though the ocean is salt, yet certain seas do not contain so much as others; my reader must not therefore conclude that the chloride of sodium, or salt, is equally diffused in sea-water, for the atmosphere receives a larger or lesser amount by reason of evaporation. Dr. Draper writes that the “temperature of the Mediterranean is twelve degrees higher than that of the Atlantic, and since much of the water is removed by evaporation, it is necessarily more saline than that ocean.” It is said that the southern seas are slightly more salt than the northern, the reason for which phenomenon has not been, as yet, satisfactorily explained. It is strange that salt should determine the colour of the sea, and that for centuries the cause of this peculiar natural phenomenon of the ocean should have been a closed secret even to men of science. Even from the earliest times, the origin of this marine peculiarity has attracted the attention and wonder of navigators; yet, strange to say, it has only been discovered within the last few years. The many expeditions which have been despatched by the Governments of England, Germany, and others, for the express purpose of oceanic discovery, have been the means of solving a question which has perplexed all races of seamen from the time of the Phœnicians, and which astonished Columbus on his voyage to the Indies. These recent scientific investigations have proved that the proportion of salt held in solution by sea-water determines its blue or green appearance, and also its specific gravity; consequently, when the water is blue, we may conclude that it holds a much greater proportion of salt; when it is green, it is indicative that there is a decrease.