(I) Modern exploration began in the second half of the 15th century with the voyages of the great Portuguese and Spanish discoverers. (II) They were followed by sailors of other European nations. (III) In less than one hundred years the coast-lines of much of America, Africa and South-west Asia had been revealed and the globe circumnavigated. (IV) The motives of these early explorers were mixed, varying from adventure and trade to plunder and national power. (V) Further, all these problems were so interrelated that they were only solved several centuries later.