It is not a uniform speech, but comprises several dialects which have been classed by Jaeschke into three groups, namely (i) the central or the dialects of Lhasa and the central provinces of U and Tsang (including Spiti) which is the lingua franca of the whole country, (2) the western dialects of Ladak, Lahul, Baltistan and Purig, and (3) the eastern dialects of the province of Khams. In addition to these, however, are many sub-dialects of Tibetan spoken in the frontier Himalayan districts and states outside Tibet, namely, in Kunawar and Bashahr, Garhwal, Kumaon, Nepal including especially the Serpa and Murmi of eastern Nepal, Sikkim (where the dialect is called Danjong-ka), Bhutan (Lho-ka or Duk-ka.), all of which are affiliated to a central group of dialects.
Jaeschke from 1860 to 1867 made several important communications, chiefly with reference to the phonetics and the dialectical pronunciation, to the academies of Berlin and St Petersburg, and in the Journal of the Asiatic Society of Bengal.
Since then the problem has been disentangled; and now minor points only remain to be cleared up. Jaeschke devoted special attention to the dialectical sounds, and showed in several papers and by the comparative table prefixed to his dictionary that in the western and eastern dialects these sounds correspond more or less closely to the written forms.
Jaeschke first noted the existence of tones in Tibetan, and these have been found by Professor Conrady to have developed on the Tones .
462b St Petersburg) partly published by Jaeschke (Monatsber.