One of the most interesting migrations on record is that of the Yuehti from their old seats in the north-west of China to the site of the Greek kingdom of Bactria. Its interest is increased rather than diminished by the fact that we can trace its origin by the aid of authentic records, as well as from the knowledge that it was but one in a series, the original exciting cause of which still remains veiled in an obscurity apparently only to be pierced, on the one hand, by the geologist who shall work out the changes in the physical geology of Asia, within the human period, or, on the other, by the comparative mythologist, who, placing side by side the myths and traditions of its ancient inhabitants, sees, though dimly, some sort of order rising out of what, at first sight, is a veritable chaos.