The slightest movement of the air communicates motion to the surface of such a great sheet of water as the sea, and this motion is gradually increased till one ripple meets another, and the power of both goes to form the next, so that they acquire a very considerable size; when a gale of wind blows, the rolling of the waves far out at sea becomes terrific, and they rise like mountains, chasing one another over the wide ocean. But sailors rather like a smart breeze, and more especially did they a few years ago, when the wind was all they had to depend upon for onward progress. In those days a calm which would sometimes last for weeks together was to them most fearful, for it was often a source of great distress and privation, especially if short of provisions; the sea would then look like a great pool of stagnant water covered on the surface with sea-weed and animalculæ, and fearful it must have been when food was failing, and no hope of progressing but the springing-up of a wind. But, in these days, with the assistance of steam, a calm is the very time in which most progress is made, and there is no doubt but a time will come when it will be matter of wonder that men could ever have trusted to so uncertain an element as the wind; yet, if it were not for the winds, currents, and tides, the sea could not maintain its state of purity, for its saltness is not sufficient to prevent the growth of fungi and all sorts of animalculæ, which, from their decay, would produce noxious gases and be most injurious to animal life. Its constant motion alone prevents this, and the spores and germs are tossed about until destroyed and eaten up by the inhabitants of the deep who devour every kind of organic matter which is deposited in the sea, and thus it is that the waters of the ocean are so bright and clear that an object can be seen at a considerable depth.