THE OCEAN. 331 



the belief that this colour is appropriate to water in its greatest purity. Chemistry is 

 addressed in vain to explain this phenomenon, or that of the beautiful greenish blue 

 colour of ice in a mass, or that of the blue of the Rhone near Geneva. There is hitherto 

 no proof that waters exist which contain a greater or less degree of hydrogen ; and the 

 refrigeration of the seas in tempests is much too weak to permit us to attribute the 

 reflection of different coloured rays to the mere change of density. It is improbable 

 that the green colour of the water is owing to the mixture of yellow rays from the bottom, 

 and blue rays reflected by the water ; for the open sea is often green where it is more 

 than four thousand feet deep. Perhaps, at certain hours of the day, the red or yellow 

 light of the sun contributes to the colouring it green. The waves, like moveable and 

 inclined mirrors, progressively reflect the shades and tints of the atmosphere from the 

 zenith to the horizon. The motion of the surface of the water modifies the quantity of 

 light that penetrates towards the inferior strata ; and it may be conceived that these 

 rapid changes of transmission, which act as it were like changes of opaqueness, may, 

 when they are united to other causes unknown to us, change the tint of the ocean. 



The colour of the general body of the sea a blue more or less intense is far from being 

 universal. In various parts of its basin other shades appear, the causes of which are 

 local, and are due to the existence of vast numbers of minute animalcule ; to a marine 

 vegetation at or near the surface ; to the nature of the soil at the bottom, or to the 

 infusion of earthy substances in the water. The Mediterranean, towards its eastern 

 extremity, has occasionally a purple hue. In the Gulf of Guinea the sea is white ; 

 about the Malclive Islands, black ; and near the shores of California it has a reddish 

 appearance. The reddish tinge marks the waters near the mouth of the La Plata, and 

 prevails also in the Red Sea whence its name. The colour in this latter locality has 

 been definitely investigated by Ehrenberg, who refers it to the prevalence of a species of 

 Oscillatoria, a family of microscopical animalculae. In the spring of the year 1825, 

 it was observed that the waters of the Lake of Morat, in Switzerland, had almost the 

 hue of blood, which De Candolle demonstrated to proceed from an animal, figured and 

 described by the botanist under the name of Oscillatoria rubescens, which confirms the 

 conclusion of Ehrenberg respecting the peculiar tinge of the Red Sea waters. It will be 

 recollected, that on the return of Captain Ross from his first expedition to the polar seas, 

 much surprise was excited by his account of the red snow, as it was termed, observed 

 upon some of the snow mountains near the shores of Baffin's Bay. But a similar 

 phenomenon is of annual occurrence in the Alps, though not much noticed, because of 

 its occurrence at a season when few travellers visit the country. Minute red grains 

 appear scattered upon the snow in March, which usually are entirely gone by the close 

 of May. Saussure has given an account of this appearance as occurring on the Great 

 St. Bernard, but it is most abundant on Mount Breven, situated on the sunny side of 

 the valley of Chamouni. The grains penetrate two or three inches into the snow, and 

 are of a lively red colour, occurring chiefly where the snow lies in a cavity, deepest near 

 the centre, and very faint upon the borders. Saussure came to the conclusion that it 

 was the pollen of an Alpine plant, but no plant has ever been discovered in Switzerland 

 to yield such a product. A similar opinion was entertained with reference to the red 

 snow brought home by Ross, when the residue was examined, after the water had been 

 evaporated. In all probability, the red tinge observed on the Arctic and Alpine snows, 

 proceeds from precisely the same cause as that which coloured the waters of the Lake of 

 Morat, and originates the tinge of the ocean at the mouth, of the La Plata, in the Red Sea, 

 and along the coast of California the presence of minute forms of animal life. 



The waters of the ocean vary in their clearness, from a crystalline transparency to 

 a dulness bordering on opacity. Those of the North Sea, along the west coast of 



