But still, in spite of the voyages of Viking and Venetian, the Crusading expeditions, and the enterprising travels which had been undertaken, yet the real progress in navigation, as a science and an art, was made not by the sailors of Christendom, but by the Arabians. The latter had calculated their tables of latitude and longitude by astronomical observations. They had produced rough coast-charts; and what was more, they had been using the compass and other nautical instruments for some time. But thanks to the travel craze which had set in, the Christian ships which were seen in the Mediterranean about the beginning of the fifteenth century were supplied with the compass, an astrolabe, a timepiece, and charts just as you would have found on board an Arabian trading to the Indian Ocean. At length the Christian seamen overcame their prejudice, and were glad to avail themselves of the magnetised needle; but its use was by no means universal. Bear in mind, also, the wave of the New Learning that was spreading over Europe. Mathematics and astronomy had already begun to be studied in Portugal at the beginning of the fourteenth century. And with regard to cartography, or map-making, something new was happening. Already by 1306 a Venetian map had been made which put into form the ideas which inspired the first Italian voyages in the Atlantic. These charts were made for the purpose of recording the discoveries of the great contemporary seamen. It is indeed surprising to note how accurate these charts really are. The Italians with all their artistic ability were now the great map-makers, and they managed to produce a number of portolani which were of the greatest use to the mariners and merchants of the Mediterranean. These were made by means of the knowledge and assistance of seamen, and were intended to be of service to the latter in their navigation. [Illustration: FOURTEENTH-CENTURY PORTOLANO OF THE MEDITERRANEAN. Showing vague idea of the shape of Africa] A portolano was nothing more or less than a plan or map-sketch. That which is here given is from a reproduction in the Map Room of the British Museum. When we consider that this was made as far back as the year 1351, or one hundred and thirty-five years before the Cape of Good Hope was rounded, it is wonderfully accurate, and the shape given to Southern Africa is a curiously clever guess. But it should be remembered that though the continent had never been rounded (except in Phœnician times), yet there was a vague idea of the probable shape of the west coast from those who had been to Barbary; and it is most probable that by the information received from the Arabs, who knew the East African coast intimately, this side of the continent would be described to them. Thus a not wholly incorrect idea was conveyed of the shape of the whole of Africa’s coast-line.