In this undertaking[[279]] Andrea Bianco is said to have assisted, and the work was (either originally or in copy) executed for the Portuguese Government, and assisted by the same. King Affonso V supplied the draughtsmen with charts on which the recent discoveries of Prince Henry's seamen were laid down. Payment was liberal (12 to 15 sous a day to every one of the common artisans and copyists); and the Doge Francesco Foscarini, "when he witnessed the plan and the beginning of Mauro's work," trusted that Prince Henry would find therein fresh reasons for pressing on his explorations. The completed mappemonde was sent to Portugal, in charge of Stefano Trevigiano, on April 24th, 1459. This was based, perhaps, in part on the map, or maps, illustrating the voyages of Marco Polo, in the Doges' Palace in Venice, apparently on one of the walls of the Sala della Scudo. The "Polo" portions of the New Design were, however, chiefly in the Far East. In N.W. Africa, Cape Verde and Cape Rosso are marked, and near the S.W. coast of the Continent is a long inscription about the Portuguese voyages, stating that the latter "here gave new names to rivers, bays, harbours, etc., and that they made new charts, of which he (Fra Mauro) had had many in his possession." At the extreme south point of Africa is the name "Diab," with a legend telling how an Indian junk was said to have been storm-driven to this point in about 1420, and (without reaching land) to have sailed further westward for 2,000 miles during forty days. After this the Indians turned back, and after seventy days' sail, returned to Cavo di Diab, where they found on shore a huge bird's egg, as large as a barrel.[[280]] Fra Mauro had also himself spoken with a trustworthy person, who said that he had sailed from India past Sofala to "Garbin," a place located in the middle of the west coast of Africa close to "Dafur." "Fundan," again, a little south of Cape Rosso, may represent some Portuguese coast-name which has not elsewhere survived.
Yet, apart from these references, there is but little evidence of the new discoveries forthcoming, and, from a critical point of view, Fra Mauro's planisphere is somewhat disappointing. True it is in certain regions (its Mediterranean and Black Sea, for instance), of the portolano type, but in the more outlying parts of the world, and even in much of Africa, it is far more similar to one of the old Macrobius type of wheel-maps (continued in such fifteenth-century specimens[[281]] as the "Borgian" design of c. 1430), than to a specimen of enlightened cartography like the "Laurentian" example of 1351. The traditional centre at Jerusalem is not taken, but a point slightly north of Babylon serves instead. In Africa numerous tribes and cities are marked even beyond the Equator, in regions inscribed as "Inhabitabiles propter calorem;" but the general shape of the west coast is hardly satisfactory. Fra Mauro knows nothing of the great bend of the Guinea coast; N.W. Africa appears not as a great projection, but only as a gently-sloping shoulder of land; Cape Verde is not the westernmost point of the Continent. This position is given to the traditional "Promontory of Seven Mountains" (north of the Western Nile), which we have met with in earlier examples. To the south of the Green Cape appears a long and narrow inlet of sea,[[282]] which can hardly be supposed to represent in any way the South coast of "Guinea" from Sierra Leone to Benin, but perhaps is a combination and exaggeration of the great estuaries so recently visited by Henry's seamen—the Gambia, the Casamansa, the Rio Grande or Geba, and others. The Western or Negro Nile is drawn as flowing straight from Meroe in Nubia to the Atlantic, passing through a great swamp (Lake Chad?), an elongated piece of open water in the country of Melli (the Middle Niger in flood?), and the course of the Senegal. South of Cape Roxo, the coast, trending gradually south-east, exhibits a very broken contour and is fringed with many islands—evidence only too certain that the draughtsman is working by the light of imagination. Finally, although Africa is rightly conceived as on the whole projecting into the Southern Ocean, and having its length or greatest dimension from south to north rather than from east to west, it is greatly twisted out of shape by the inclination S.E., which bends round its southmost point almost to the longitude of Guzerat.[[283]] The general size of the Continent, however, is more accurately guessed[[284]] than on most maps of this or earlier time. Here Fra Mauro is nearer the truth even than the Laurentian Portolano of 1351, so far superior to the work of 1457-9 in many respects. Parallels of latitude and meridians of longitude are not indicated in the Camaldolese mappemonde, which has been sometimes referred to as "an immeasurable advance on all earlier cartography;" and the importance of this famous design, as an index to current geographical ideas, and as a world-picture of great size and magnificence, possessing in its time considerable official importance, must not lead us to take it as an example of cartographical perfection.
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The use of the magnetic needle is essentially connected with the portolan type of map; this instrument was well known to Prince Henry's sailors, and is referred to by the Infant himself as being, like the sailing chart, a necessity for navigators.[[285]] But it could hardly come into general employment till men reached beyond the mediæval stage of a magnetic needle enclosed in a tube so as to float on water.
In the Discovery of the Compass four stages may be distinguished:
(1) The discovery of a species of stone with polar-magnetic qualities, i.e., with the power of attracting iron.
(2) The discovery that steel or hardened iron could be made polar-magnetic by rubbing it with a lode-stone.
(3) The discovery that the magnet (or magnetised iron) possessed the quality of definite direction, one of its poles always indicating the north, if it were so supported or suspended that it could move freely.
(4) The discovery of using the magnetised iron needle as a compass.
The first dates from a high antiquity, and is noticed by Plato, Theophrastus, Pliny, Ptolemy, Claudian, and many writers of the Mediæval as well as of the Classical period. The subsequent advances we cannot date, for Europe, earlier than the twelfth century; when Alexander Neckam and Guyot de Provins (c. 1190-1200) show us that some investigators had advanced as far as the third of the stages above recounted.