CHAPTER V. A VOYAGE ON A TROPICAL SEA. To you, my little friends, who have always lived in a climate in which it seems as if the wind changed, and it became sun-shiny or cloudy, wet or dry, cold or hot, without any law or regularity, it is something strange to hear of places where the inhabitants know almost to a day that the wind will blow constantly in one direction during so many months in the year, and constantly in some other direction during the rest: and where, with equal certainty, they know when to expect rain and when fine weather. The truth is, our changeable weather is under the influence of laws quite as certain and fixed as their uniform weather is, only that there are more partial causes operating in our climate, so that the effects are not so strictly periodical. We know as little about the way in which the laws operate in one case, as in the other. The winds that always blow in one direction are called the Trade Winds, and those which blow in one direction regularly during a certain portion of the year, are called monsoons. They make navigation in some parts of the ocean, very certain, and you cannot think how odd it seems to a young sailor the first time he sails in them. He leads then a lazy sort of life; there is no tacking about, but day after day he has nothing to do but just such things as might be done on land. When the sailors of Columbus first found themselves in the Trade Wind blowing from the eastward, having sailed before it for many days, they gave themselves up to despair, because they thought they should never be able to make their way back against it to their dear native country. They did not know that it would by and by blow quite as certainly in another direction. These uniform winds blow only within a certain distance of the equator, and the cause of them is this. The heat of the climate there occasions the air next to the surface of the earth to be always ascending, and other air rushes in from other parts of the world to supply its place. The motion of the earth upon its axis operates with this, by bringing the parts of its surface successively in contact with any certain point in the atmosphere, which does not revolve so rapidly as the earth itself, and a fixed direction is thus given to the wind. But it is still much more dull to find one's self in a calm on a tropical sea. Only imagine to yourselves a stagnant and shoreless sea, often with unsightly masses of sea-weed floating on it, a sky constantly of a gloomy-looking red, and nothing to be seen day after day except this sky and sea; insupportable thirst and bad water to quench it, and the ship all the time rocking to and fro with a nasty dull motion, and the ropes and sails idly flapping against the mast and yards. But though I have seen and felt all this, I cannot describe it to you so well as the poet, so I will give you his words.