PERHAPS the most exciting period in European history is that known as the Age of Discovery, which began toward the end of the fourteenth century and lasted well into the nineteenth. The inertia of the Dark Ages was thrown off, curiosity was aroused by tales of distant lands, and commercial rivalries began to flourish. Adventurers flocked to the maritime nations to sign up on the ships being built with feverish speed. Portugal and Spain became a center for research and instruction in the arts of navigation, cosmography, and cartography. Ship captains and expedition leaders were given instruction before setting forth, and those lucky enough to return contributed additional knowledge and technical advice. Ships began to creep down the west coast of Africa, venturing farther and farther into the dread Sea of Darkness. Africa was rounded, and ships sailed north and then east to the fabulous Indies and to China. Finally the Atlantic was conquered. The early Portuguese and Spanish navigators rendered an unparalleled service to the world by their enterprise in exploration. Expert cosmographers, surveyors, and artists were sent out with each ship to record and map discoveries. Modern science has made it possible to reproduce these magnificent early maps, and historians have utilized the accumulated data to interpret and analyze them. The last decade has been especially active in such reproduction. Many of these treasures appear in monumental volumes, which, although they allow the reader to examine the maps in their original sizes, create a problem in filing.