Not until the next year, 1497, did John Cabot set out. Then he embarked from Bristol with a single ship, called in an old history the Matthew, and a crew of eighteen men. First, he sailed round the south of Ireland, and from there struck out westward into the unknown sea. The appliances of navigation were then very imperfect. Sailors could reckon the latitude by looking up at the North Star, and noting how high it was above the horizon. Since the North Star stands in the sky due north, and the axis on which the earth spins points always towards it, it will appear to an observer in the northern hemisphere to be as many degrees above the horizon as he himself is distant from the pole or top of the earth. The old navigators, therefore, could always tell how far north or south they were. Moreover, as long as the weather was clear they could, by this means, strike, at night at least, a course due east or west. But when the weather was not favourable for observations they had to rely on the compass alone. Now the compass in actual fact does not always and everywhere point due north. It is subject to variation, and in different times and places points either considerably east of north or west of it. In the path where Cabot sailed, the compass pointed west of north; and hence, though he thought he was sailing straight west from Ireland, he was really pursuing a curved path bent round a little towards the south. This fact will become of importance when we consider where it was that Cabot landed. For finding distance east and west the navigators of the fifteenth century had no such appliances as our modern chronometer and instruments of observation. They could tell how far they had sailed only by 'dead reckoning'; this means that if their ship was going at such and such a speed, it was supposed to have made such and such a distance in a given time. But when ships were being driven to and fro, and buffeted by adverse winds, this reckoning became extremely uncertain.