The total addition of these mediæval travels to geographical knowledge consisted mainly in the addition of a wider extent of land in China, and the archipelago of Japan, or Cipangu, to the map of the world. The accompanying map displays the various travels and voyages of importance, and will enable the reader to understand how students of geography, who added on to Ptolemy's estimate of the extent of the world east and west the new knowledge acquired by Marco Polo, would still further decrease the distance westward between Europe and Cipangu, and thus prepare men for the voyage of Columbus. [_Authorities:_ Sir Henry Yule, _Cathay and the Way Thither_, 1865; _The Book of Ser Marco Polo_, 1875.] CHAPTER V ROADS AND COMMERCE We have now conducted the course of our inquiries through ancient times and the Middle Ages up to the very eve of the great discoveries of the fifteenth and sixteenth centuries, and we have roughly indicated what men had learned about the earth during that long period, and, how they learned it. But it still remains to consider by what means they arrived at their knowledge, and why they sought for it. To some extent we may have answered the latter question when dealing with the progress of conquest, but men did not conquer merely for the sake of conquest. We have still to consider the material advantages attaching to warfare. Again when men go on their wars of discovery, they have to progress, for the most part, along paths already beaten for them by the natives of the country they intend to conquer; and often when they have succeeded in warfare, they have to consolidate their rule by creating new and more appropriate means of communication. To put it shortly, we have still to discuss the roads of the ancient and mediæval worlds, and the commerce for which those roads were mainly used.