But notwithstanding these errors, which were due partly to the roughness of the materials which he had to deal with, and partly to scientific caution, Ptolemy's work is one of the great monuments of human industry and knowledge.

For the Old World it remained the basis of all geographical knowledge up to the beginning of the last century, just as his astronomical work was only finally abolished by the work of Newton.

Ptolemy has thus the rare distinction of being the greatest authority on two important departments of human knowledge--astronomy and geography--for over fifteen hundred years.

Into the details of his description of the world it is unnecessary to go.

The map will indicate how near he came to the main outlines of the Mediterranean, of Northwest Europe, of Arabia, and of the Black Sea.