consisting of sulphuretted hydrogen, hydrochlorate of ammonia, iodine iron, copper, and even silver in various quantities and proportions, according to the locality of the specimen. In examining the plates of copper taken from the bottom of a ship at Valparaiso, which had been long at sea, distinct traces of silver were found deposited by the sea. Finally, we find dissolved in the ocean a peculiar mucus, which seems of a mixed animal and vegetable nature, and is evidently organic matter proceeding from the successive decomposition of the innumerable generations of animals which have disappeared since the beginning of the world. This matter has been described by the Count Marsigli, who designates it sometimes under the name of _glu_, and sometimes as an _unctuosity_. It is the "ooze" of marine surveyors, and consists chiefly of carbonate of lime, ninety per cent. of which is formed of minute animal organisms. Its mealy adhesiveness results from the pressure of the superimposed water. The numerous salts which exist in the sea can neither be deposited in its bed, nor exhaled with the vapour, to be again poured upon the soil in showers of rain. Particular agents retain these salts in solution, transform them, and prevent their accumulation. Hence sea water always maintains a certain degree of saltness and bitterness, and the ocean continues to present the chemical characters which it has exhibited in all times, varying only in certain localities where more or less fresh water is poured into the sea basin from rivers: thus the saltness of the Mediterranean is greater than that of the ocean, probably because it loses more water by evaporation than it receives from its fresh-water affluents. For the opposite reason, the Black and the Caspian Seas are less charged with these salts. The Dead Sea is so strongly impregnated with salt that the body of a man floats on its surface without sinking, like a piece of cork upon fresh water. The supposed cause is excessive evaporation and the absence of rivers of any importance.