350 THE PULSE OF ASIA
temporary materials. One shows a bifurcation of the Oxus; another shows the river as entering the Sea of Aral ; and a third as entering the Caspian. The majority show an enlarged Caspian and no Aral. Humboldt says of them : " The maps of the Middle Ages, of which I have made a particular study, seem to indicate that the Scythian gulf of the Caspian [was] much more extended to the east than in our day, [and] has by mistake been made to include all the lake of Aral."
To sum up our conclusions as to the Caspian during the Middle Ages, there can be little doubt that the level of the sea has been influenced by changes in the course of the Oxus River. On the whole, however, the fluctuations of the lake do not correspond to the variations of the course of the river; and the influence of the Oxus appears to have been of minor importance compared to that of some other factor. At most, only a part; of its water ever seems to have reached the Caspian, and even that for only a few centuries, from about 1200 to 1550 A. D. at the outside, during the time designated as the " Oxus Period " in the diagram. It is probable, moreover, that the Oxus never flowed permanently to the Caspian, but intermittently for a few score years at a time. As early as 920 A. D., the sea had attained a high level, but it was not till three centuries later that the Oxus was first diverted to it. Again, the last notable contribution of the river to the sea had come to an end before 1550, but the sea remained at a high level till at least 1638. Thus it appears that the mediæval high stand of the Caspian was not due to the diversion of the Oxus, but to some other cause, and that cause appears to have been climatic.
IIIFカラー高解像度
