They certainly extended their voyages to Greenland, and there is a good deal of evidence for believing that they travelled from Greenland to Labrador and Newfoundland. In the year 1001, an Icelander named Biorn, sailing to Greenland to visit his father, was driven to the south-west, and came to a country which they called Vinland, inhabited by dwarfs, and having a shortest day of eight hours, which would correspond roughly to 50° north latitude. The Norsemen settled there, and as late as 1121 the Bishop of Greenland visited them, in order to convert them to Christianity. There is little reason to doubt that this Vinland was on the mainland of North America, and the Norsemen were therefore the first Europeans to discover America. As late as 1380, two Venetians, named Zeno, visited Iceland, and reported that there was a tradition there of a land named Estotiland, a thousand miles west of the Faroe Islands, and south of Greenland. The people were reported to be civilised and good seamen, though unacquainted with the use of the compass, while south of them were savage cannibals, and still more to the south-west another civilised people, who built large cities and temples, but offered up human victims in them. There seems to be here a dim knowledge of the Mexicans. The great difficulty in maritime discovery, both for the ancients and the men of the Middle Ages, was the necessity of keeping close to the shore. It is true they might guide themselves by the sun during the day, and by the pole-star at night, but if once the sky was overcast, they would become entirely at a loss for their bearings. Hence the discovery of the polar tendency of the magnetic needle was a necessary prelude to any extended voyages away from land. This appears to have been known to the Chinese from quite ancient times, and utilised on their junks as early as the eleventh century. The Arabs, who voyaged to Ceylon and Java, appear to have learnt its use from the Chinese, and it is probably from them that the mariners of Barcelona first introduced its use into Europe. The first mention of it is given in a treatise on Natural History by Alexander Neckam, foster-brother of Richard, Coeur de Lion. Another reference, in a satirical poem of the troubadour, Guyot of Provence (1190), states that mariners can steer to the north star without seeing it, by following the direction of a needle floating in a straw in a basin of water, after it had been touched by a magnet. But little use, however, seems to have been made of this, for Brunetto Latini, Dante's tutor, when on a visit to Roger Bacon in 1258, states that the friar had shown him the magnet and its properties, but adds that, however useful the discovery, "no master mariner would dare to use it, lest he should be thought to be a magician." Indeed, in the form in which it was first used it would be of little practical utility, and it was not till the method was found of balancing it on a pivot and fixing it on a