The whole of Gobi is regarded by Pumpelly as having formed a portion of a great ocean, which, in comparatively recent geological times, extended south to the Caspian and Black Seas, and between the Ural and Inner Hing an Mountains, and was drained off by an upheaval whose traces and effects can be detected in many parts. “It appears to me,” he adds, “that the ancient physical geography of this region, and the effects of its elevation, present one of the most important fields of exploration.” It will no doubt soon be more fully explored. Baron Richthofen describes Central Asia as properly a shallow trough, 1,800 miles long and about 400 miles wide, whose bottom is about 1,800 feet above the ocean; its ancient shore-line extended between the Kwănlun and Tien shan ranges on the west, from 5,000 to 10,000 feet high, and gradually falling to 3,600 feet in its eastern shore. This is the _Han-hai_; eastward is _Sha-moh_, and outside of both these wildernesses are the peripheral regions, where the waters flow to the ocean, carrying their silt, the erosions from the mountains. Inside of the shore-line nothing reaches the oceans, and these results of degradation are washed or blown into the valleys, and the country is buried in its own dust.[9] The _rivers_ of China are her glory, and no country can compare with her for natural facilities of inland navigation. The people themselves consider that portion of geography relating to their rivers as the most interesting, and give it the greatest attention. The four largest rivers in the empire are the Yellow River, the Yangtsz’, the Amur, and the Tarim; the Yaru-tsangbu also runs more than a thousand miles within its borders. ~THE YELLOW RIVER.~