The area between the northern border of the Persian high lands and the Caspian and Aral Seas is a nearly desert low-lying plain, extending to the foot of the north - western extremity of the great Tibeto-Himalayan mountains, and prolonged east- Trans- ward up the valleys of the Oxus (Amu-Darya) and Caspian Jaxartes (Syr-Darya), and northward across the country re ior, and of the Kirghiz to the south-western border of Siberia.
The north-western extremity of the elevated Tibeto-Himalayan mountain plateau is situated about on 73° E.
Linguistically, Tibetan is allied to the Burmese languages, and forms with the latter a family of the so-called Turano-Scythian stock called " Tibeto-Burman " (q.v.), the unity of which family was first recognized by Brian Hodgson in 1828, and indeed several of the dialects of Tibetan are still only known through the copious vocabularies collected by him.
Pere Desgodins in 1899 issued from Hong-Kong a large Tibeto-LatinFrench dictionary, Dictionnaire thibetain-latin francais.
In the 9th century, as shown by the bilingual Tibeto-Chinese edict at Lhasa, there was relatively little difference between the spoken and the written language.