Some of these characters--wavy hair, aquiline nose, hazel eye, rosy cheeks--are not Mongolic, and despite W. W. Rockhill's certificate of racial purity, one is led to suspect a Caucasic strain, perhaps through the neighbouring Salars. These are no doubt sometimes called Kara-Tangutans, "Black Tangutans," from the colour of their tents, but we learn from Potanin, who visited them in 1885[387], that they are Muhammadans of Turki stock and speech, and we already know[388] that from a remote period the Turki people were in close contact with Caucasians. The Salars pitch their tents on the banks of the Khitai and other Yang-tse-Kiang headstreams. That the national name Bod-pa must be of considerable antiquity is evident from the Sanskrit expression _Bhotiya_, derived from it, and long applied by the Hindus collectively to all southern Tibetans, but especially to those of the Himalayan slopes, such as the Rongs (Lepchas) of Sikkim and the _Lho-pa_ dominant in Bhutan, properly _Bhot-ant_, that is, "Land's End"--the extremity of Tibet. Eastwards also the Tibetan race stretches far beyond the political frontiers into the Koko-nor region (Tanguts), and the Chinese province of Se-chuan, where they are grouped with all the other Si-fan aborigines. Towards the south-east are the kindred _Tawangs_, _Mishmi_, _Miri_, _Abor_[389], _Daflas_, and many others about the Assam borderlands, all of whom may be regarded as true Bhotiyas in the wild state. Through these the primitive Tibetan race extends into Burma, where however it has become greatly modified and again civilised under different climatic and cultural influences. Thus we see how, in the course of ages, the Bod-pa have widened their domain, radiating in all directions from the central cradle-land about the Upper Brahmaputra (San-po) valley westwards into Kashmir, eastwards into China, southwards down the Himalayan slopes to the Gangetic plains, south-eastwards to Indo-China. In some places they have come into contact with other races and disappeared either by total extinction or by absorption (India, Hindu-Kush), or else preserved their type while accepting the speech, religion, and culture of later intruders. Such are the _Garhwali_, and many groups in Nepal, especially the dominant _Gurkhas_ (_Khas_[390]), of whom there are twelve branches, all Aryanised and since the twelfth century speaking the _Parbattia Bhasha_, a Prakrit or vulgar Sanskrit tongue current amongst an extremely mixed population of about 2,000,000. In other directions the migrations took place in remote prehistoric times, the primitive proto-Tibetan groups becoming more and more specialised as they receded farther and farther from the cradle-land into Mongolia, Siberia, China, Farther India, and Malaysia. This is at least how I understand the peopling of a great part of the eastern hemisphere by an original nucleus of Mongolic type first differentiated from a pleistocene precursor on the Tibetan tableland.