But Columbus, though he knew that his explanation was wrong, said the compass was all right. The North Star, toward which the needle always pointed, had, so he said, changed its position. This quieted the sailors for a while. When they had been about forty days out from Palos, the ship ran into what is marked upon your maps as the Sargasso Sea. This is a vast meadow of floating seaweed and seagrass in the middle of the Atlantic; it is kept drifting about in the same place by the two great sea currents that flow past it but not through it. The sailors did not know this, of course, and when the ships began to sail slower and slower because the seaweed was so thick and heavy and because there was no current to carry them along, they were sure that they were somewhere near to the jumping-off place, and that the horrible monsters they had heard of were making ready to stop their ships, and when they had got them all snarled up in this weed to drag them all down to the bottom of the sea. For nearly a week the ships sailed over these vast sea-meadows, and when they were out of them they struck what we call the trade-winds--a never-failing breeze that blew them ever westward. Then the sailors cried out that they were in an enchanted land where there was but one wind and never a breeze to blow the poor sailors home again. Were they not fearfully "scarey?" But no doubt we should have been so, too, if we had been with them and knew no more than they did. And when they had been over fifty days from home on the twenty-fifth of September, some one suddenly cried Land! Land! And all hands crowded to the side. Sure enough, they all saw it, straight ahead of them--fair green islands and lofty hills and a city with castles and temples and palaces that glittered beautifully in the sun. Then they all cried for joy and sang hymns of praise and shouted to each other that their troubles were over. Cathay, it is Cathay! they cried; and they steered straight for the shining city. But, worst of all their troubles, even as they sailed toward the land they thought to be Cathay, behold! it all disappeared--island and castle and palace and temple and city, and nothing but the tossing sea lay all about them. For this that they had seen was what is called a mirage--a trick of the clouds and the sun and the sea that makes people imagine they see what they would like to, but really do not. But after this Columbus had a harder time than ever with his men, for they were sure he was leading them all astray.