"A few days after leaving Bahia," says Mr. Darwin, "not far from the Abrolhos islets, the whole surface of the water, as it appeared under a weak lens, seemed as if covered by chipped bits of hay with their ends jagged. Each bundle consisted of from twenty to sixty filaments, divided at regular intervals by transverse septa, containing a brownish-green flocculent matter. The ship passed several bands of them, one of which was about ten yards wide, and, judging from the mud-like colour of the water, at least two and a half miles long. Similar masses of floating vegetable matter are a very common appearance near Australia. During two days preceding our arrival at the Keeling Islands, I saw in many parts masses of flocculent matter of a brownish green colour, floating in the ocean. They were from half to three inches square, and consisted of two kinds of microscopical confervæ. Minute cylindrical bodies, conical at each extremity, were involved in large numbers in a mass of fine threads." "On the coast of Chili," says the same author, "a few leagues north of Conception, the 'Beagle' one day passed through great bands of muddy water; and again, a degree south of Valparaiso, the same appearance was still more extensive. Mr. Sulivan, having drawn up some water in a glass, distinguished by the aid of a lens moving points. The water was slightly stained, as if by red dust, and after leaving it for sometime quiet, a cloud collected at the bottom. With a slightly magnifying lens, small hyaline points could be seen darting about with great rapidity, and frequently exploding. Examined with a much higher power, their shape was found to be oval, and contracted by a ring round the middle, from which line curved little setæ proceeded on all sides, and these were the organs of motion. Their minuteness was such that they were individually quite invisible to the naked eye, each covering a space equal only to the one-thousandth of an inch, and their number was infinite, for the smallest drop of water contained very many. In one day we passed through two spaces of water thus stained, one of which alone must have extended over several square miles. The colour of the water was like that of a river which has flowed through a red clay district, and a strictly defined line separated the red stream from the blue water." In the neighbourhood of Callao, the Pacific has an olive-green colour, owing to a greenish matter which is also found at the bottom of the sea, in a depth of 800 feet. In its natural state it has no smell, but when cast on the fire, it emits the odour of burnt animal substances. Near Cape Palmas, on the coast of Guinea, Captain Tuckey's ship seemed to sail through milk, a phenomenon which was owing to an immense number of little white animals swimming on the surface, and concealing the natural tint of the water.