But his discoveries were neither appreciated nor applied to any practical use till long after his time. About a century and a half after Hipparchus, Strabo, a Greek of Pontus and a great traveller, wrote a geography which embodies all that was known of the science at the beginning of the Christian era. The countries immediately around the Mediterranean were known with tolerable accuracy; but the Atlantic shores of Europe were very erroneously comprehended, while of the northern and eastern portions only the vaguest ideas were entertained. Nothing whatever was positively known of Scandinavia, Russia, or northern Germany. The extent of Europe to the east and northeast was greatly exaggerated, while that of Asia was proportionally underrated. Nothing was known of Siberia, Tartary, China, Japan, or the great Asiatic archipelago. The Ganges was thought to have throughout an easterly course, and to flow into the eastern ocean. The Caspian was supposed to be the limit of the earth to the north, and to be connected with the eastern ocean by a sea occupying the space now known to be covered by Siberia and Tartary. Of Africa only the northern part was known, south of which was thought to be an uninhabited and uninhabitable torrid zone.

The belief in the probability of circumnavigating Africa, which had existed in previous ages, was rejected by Strabo, though he held to the theory of an encircling ocean. The earliest Roman geographer was Pomponius Mela, who wrote about the time of the emperor Claudius. In his treatise Be Situ Orb is he explains the division of the world into two hemispheres: the northern that part of the earth which is known, the southern that which is unknown. The former is divided into three great divisions, Europe including all N. of the Mediterranean and W. of the Tanais, Africa all S. of the Mediterranean and W. of the Nile, and Asia all the remainder. A still more famous geographer was Ptolemy, who lived at Alexandria about the middle of the 2d century after Christ. At this period the Roman empire had reached its greatest extent, and all its provinces had been surveyed and were well known. Large advances had been made in the knowledge of the countries outside of the empire. The notion of a circumambient ocean had been given up, and an indefinite expanse of terra incognita substituted as the supposed boundary of the world.

Africa was represented as stretching indefinitely south, and it was even carried round to join the east of Asia, so that the Indian oeean was enclosed like the Mediterranean. In Europe, Spain and Gaul were for the first time correctly delineated, together with the southern part of Britain. The outline of Scotland and the relative position of Ireland are very incorrectly given. Thule is laid down as an island upward of 100 m. long. From its position it is probable that some part of Norway was meant. Northern Germany and the southern line of the Baltic coast were tolerably well known, as was also some portion of Russia in the neighborhood of the Baltic and the southern part of Russia in Europe. In Asia, great regions had become known sufficiently to make it certain that they were inhabited by nomad tribes called Scythians, while from the far east some vague report of China and of the regions now known as Chin-India had reached the geographer. From the time of Ptolemy till the revival of letters in Europe little progress was made in geographical knowledge. In the 9th century, however, the Northmen discovered Greenland, and in the 10th, according to their sagas, visited the North American continent.

In the 13th century missions were sent by the popes into remote parts of Asia. Father John do Piano Carpini, with some Franciscan monks, was sent in 1246 by Innocent IV. to Kayuk Khan, the Tartar emperor, and penetrated as far as Thibet. In 1253 Rubruquis, another Franciscan, was sent by Louis IX. of France in search of Prester John, and penetrated further into Asia than any European ever had before. But the greatest discoveries in this quarter were made by Marco Polo, a Venetian, who in 1271 set out with his father and uncle on a journey to the court of Kublai Khan, the Tartar conqueror of China. After travelling for more than three years they reached Yehking, near where Peking now stands. Marco Polo resided 24 years in the East, and on his return gave an account of his travels, which first made known to Europe the existence of Japan and many of the East Indian islands and countries. In the 15th century the spirit of enterprise and geographical exploration was strongly aroused in Europe. Portugal took the lead, and made great and systematic efforts to explore the unknown countries on the W. coast of Africa. In the year 1412 Cape ,Nun was doubled, and soon afterward the islands of Porto Santo and Madeira were discovered.

In 1484 Benin and Congo were discovered, and the coast explored for 1,500 m. S. of the equator. In 1486 the cape of Good Hope was reached, and 11 years later doubled by Vasco da Gama. But the greatest of all geographical discoveries was that of the new world by Christopher Columbus in 1492. From this time forward the progress of geographical exploration was exceedingly rapid. Within 30 years from the date of the first voyage of Columbus the whole E. coast of America from Greenland to Cape Horn had been explored, and Spanish keels were floating on the Pacific ocean. In 1520 Magalhaens passed the strait which bears his name, crossed the Pacific, and although he was killed in the Philippine islands, his vessel, crossing the Indian ocean, returned to Europe by way of the cape of Good Hope, having been the first to circumnavigate the globe. The W. coast of America, with the exception of that portion N. of the bay of San Francisco, was explored before the middle of the 16th century, while considerable progress was made by the Spaniards in acquiring a knowledge of the interior of South America. At the same time discovery in the East advanced with rapid strides.