It is in the region occupied by the closely approaching upper basins, lying west of the Yun-ling and north of the Assam and Himalaya system, that we must seek for the cause of the resemblance between the languages of the Irawadi and those of the Hoang-ho. This mountain land, with the eastern and southern divisions of the lower region proceeding from it, is at once united and insulated by nature. From the angle formed by the approximation of the Himalaya and Yun-ling systems, the compressed river courses again diverge, ascending to the west and north west through the elevated basins between the mountain ranges of eastern Tibet ;