The point of the story lies in its revelation as regards connection between Central Asia and India in the early centuries A.D. Clearly there was no pass unknown or unvisited by the Chinese. Not merely the direct routes, but all the connecting ways which linked up one Buddhist centre with another were equally well known. What has required from us a weary process of investigation to overcome the difficulties of map-making, was to them, if not exactly an open book, certainly a geographical record which could be turned to practical use, and it is instructive to note the use that was made of it. As a pious duty, bristling with difficulty and danger, travel over the wandering tracks which pass through the northern gates of the Himalayas was regarded with fervour; but it may be taken for granted that less pious-minded adventurers than the Chinese pilgrims would most certainly have made good use of that geographical knowledge to exploit the riches of India had such a proceeding been possible. We know that attempts have been made. From the earliest times the Mongol hordes of China and Central Asia have been directed on India, and no gateway which could offer any possible hope of admittance has been neglected. Baktria (Badakshan), lying beyond the mountain barrier, had been at their mercy. The successors to Alexander's legions in that country were swamped and dispersed within a century or two of the foundation of the Greek kingdom; and the Kabul River way to India has let in army after army. But these northern passes have not only barred migratory Asiatic hordes through all ages, but have proved too much even for small organized Mongol military expeditions.