On the second day after leaving the Canary Islands they made but eighteen miles, owing to light winds. As Columbus foresaw that nothing would intimidate his ignorant crew so much as the length of the voyage, he decided to play an innocent trick upon them by keeping one reckoning of distance for himself and another for them. He told them therefore that they had sailed only the first fifteen miles westward. On the twelfth of September, six days after their departure, they had sailed one hundred and fifty miles to the west of the Canary Island of Ferro. On that day they observed the trunk of a great tree which evidently had been drifting about a long time. The sailors took it for a sign that land was not far distant and felt much encouraged, but the encouragement did not last long, for after sailing about fifteen miles farther a strange thing happened which astonished them all and even excited the wondering Columbus—the compass needle, which had steadily pointed to the pole star, changed a whole degree to the west from its customary direction. The phenomenon was new to Columbus, as well as to his sailors. The latter were greatly excited and declared the earth was out of joint, for the needle no longer pointed right. The distance which they had traversed already seemed to them endless although their leader insisted that he was not a third of a mile out of his reckoning, but now all seemed hopeless since the needle, their only guide, had abandoned them. Columbus, whose ingenuity in discovering methods of reassuring his weak companions was inexhaustible, invented a plausible reason for this unexpected phenomenon which quieted them though it was far from being satisfactory to himself. In an ingenious manner he altered the action of the compass so that the needle pointed right again. Hardly had the crew recovered from this shock before a new trouble arose. They had come to the region of the trade-winds, which were unknown at that time. They shuddered as they thought that if these winds continued to blow they might never reach home again. One unfortunate thing followed another. On the sixteenth of September their fear was greatly increased. They suddenly observed that the ocean, as far as the eye could reach, was covered so completely with a green weed that it seemed as if they were sailing over a vast meadow.[14] In some places it was so thick they could hardly make their way through it. The sailors said to themselves, “We have come to the end of the navigable ocean. Under this sea-weed there must be reefs and shallows which will wreck our vessels. Why should we, wretched unfortunates, longer consent to follow this foolhardy leader?” Columbus again quieted them and inspired fresh hope. He said to them, “Why should you be troubled about a matter which shows that we are now approaching the wished-for goal? Does not vegetation grow by the sea? Is it not certain that we are not far from the shores where this sea-weed grew?”