But among maps of special regions the most notable are those known as Portolano maps, which were sailing charts accompanying the Portolani, or sailing directions for the Mediterranean Sea. These, no doubt, existed long before the Crusades, in connection with which they first come to our knowledge. They are in most respects remarkably accurate. They are distinguished by groups of rhumb-lines radiating from a series of centres, and marked usually with the initials of the names of the principal winds. As the accuracy of these maps was probably improved largely as the mariners’ compass came into use, it may be mentioned that the first European notice of the use of that instrument is provided by the English scientist Alexander Neckam (1157–1217) of St. Albans, foster brother to King Richard I. From his mention it appears by this time to have been a familiar object. The chief centres for the production of Portolano maps were naturally those identified in an important degree with over-sea commerce; such were Genoa, Venice, Ancona, and Majorca, while the seamen of Catalonia were also prominent at this period. These maps were in some cases extended to cover lands and seas beyond the immediate Mediterranean area, and even the whole world. World maps were usually circular with Jerusalem as a centre, and, in contrast to their accuracy in respect of the Mediterranean, they were not distinguished as a rule for much regard to the best sources of information, though for that we have already adduced some measure of excuse. The map of the world by Petrus Vesconte of Genoa (_c._ 1320) shows the Mediterranean and the Black Seas well, the Nile fairly, the Caspian indifferently, Scandinavia badly. A mountain range extends west and east across almost the whole of northern Europe and central Asia; rivers drain southward to the Black Sea from this; the Indian Ocean appears as a gulf; the south-eastward extension of the African coast is retained, and the peninsular form of India is not realized. Subsequent cartographers disagreed on such points as this last. Thus in a Florentine map of about 1350, called the Laurentian or Medicean Portolano, the west coast of India is well shown, and the influence of Marco Polo’s travels is to some degree apparent. This map, moreover, has other details of interest, such as the first appearance in any known map of the Azores and the islands of Madeira with their modern names. The Catalan map of 1375 recognizes the peninsular form of India for the first time, and Marco Polo’s results are shown to be thoroughly appreciated; and yet a century later the old errors as to the form of India and Ceylon persist even in a map so excellent in many directions as that of Fra Mauro (1457). CHAPTER V. PORTUGUESE EXPANSION AND THE REVIVAL OF PTOLEMY