219. AIDS TO EXPLORATION
THE COMPASS
The new knowledge gained by European peoples about the land routes of Asia was accompanied by much progress in the art of ocean navigation. First in importance came the compass to guide explorers across the waters of the world. The Chinese appear to have discovered that a needle, when rubbed with a lodestone, has the mysterious power of pointing to the north. The Arabs may have introduced this rude form of the compass among Mediterranean sailors. The instrument, improved by being balanced on a pivot so that it would not be affected by choppy seas, seems to have been generally used by Europeans as early as the thirteenth century. It greatly aided sailors by enabling them to find their bearings in murky weather and on starless nights. The compass, though useful, was not indispensable; without its help the Northmen had made their distant expeditions in the Atlantic.
NAUTICAL INSTRUMENTS
The astrolabe, which the Greeks had invented and used for astronomical purposes, also came into Europe through the Arabs. It was employed to calculate latitudes by observation of the height of the sun above the horizon. Other instruments that found a place on shipboard were the hour- glass, minute-glass, and sun-dial. A rude form of the log was used as a means of estimating the speed of a vessel, and so of finding roughly the longitude.
[Illustration: AN ASTROLABE]
OTHER IMPROVEMENTS IN NAVIGATION
During the last centuries of the Middle Ages the charting of coasts became a science. A sailor might rely on the "handy maps" (portolani) which outlined with some approach to accuracy the bays, islands, and headlands of the Mediterranean and adjacent waters. Manuals were prepared telling the manner about the tides, currents, and other features of the route he intended to follow. The increase in size of ships made navigation safer and permitted the storage of bulky cargoes. For long voyages the sailing vessel replaced the medieval galley rowed by oars. As the result of all these improvements navigators no longer found it necessary to keep close to the shore, but could push out dauntlessly into the open sea.
MOTIVES FOR EXPLORATION
Many motives prompted exploration. Scientific curiosity, bred of the Renaissance spirit of free inquiry, led men to set forth on voyages of discovery. The crusading spirit, which had not died out in Europe, thrilled at the thought of spreading Christianity among heathen peoples. And in this age, as in all epochs of exploration, adventurers sought in distant lands opportunities to acquire wealth and fame and power.
THE COMMERCIAL MOTIVE
Commerce formed perhaps the most powerful motive for exploration. Eastern spices—cinnamon, pepper, cloves, nutmeg, and ginger—were used more freely in medieval times than now, when people lived on salt meat during the winter and salt fish during Lent. Even wine, ale, and medicines had a seasoning of spices. When John Ball [8] wished to contrast the easy life of the lords with the peasants' hard lot, he said, "They have wines, spices, and fine bread, while we have only rye and the refuse of the straw." [9] Besides spices, all kinds of precious stones, drugs, perfumes, gums, dyes, and fragrant woods came from the East. Since the time of the crusades these luxuries, after having been brought overland by water to Mediterranean ports, had been distributed by Venetian and Genoese merchants throughout Europe. [10] But now in the fifteenth century two other European peoples—the Portuguese and Spaniards—appeared as competitors for this Oriental trade. Their efforts to break through the monopoly enjoyed by the Italian cities led to the discovery of the sea routes to the Indies. The Portuguese were first in the field.