I am reading this passage in a book called Overland to China (1900) which on page 66 makes mention of a Tiursk tribe in Central Asia.
Online searches didn't provide much details except referencing/associating other groups to the Tiursk.
Language of the Jakuts belongs to the Tiursk nationalities. (see OnlineLibrary.Wiley.com)
My guess is that it's a Russian word form for Turk/Turkic. But I want to be sure because the google translation is not the same.
Your link to the Jakut article holds what I would consider fairly strong evidence. The article (all emphasis mine) specifies that by
features, as well as by their language, the Jakuts belong to the Tiursk nationalities.
We can look to the wiki article on the Jakuts and find that
The Yakut language belongs to the Siberian branch of the Turkic languages.
Another older work, The Polar World: a Popular Description of Man and Nature in the Arctic and Antarctic Regions of the Globe By Georg Hartwig, published in 1859, has a chapter on the Jakuts. This also mentions this language connection to the Turkic people:
Though of a Mongolian physiognomy their language which is said to be intelligible at Constantinople distinctly points to a Turk extraction and their traditions speak of their original seats as situated on the Baikal and Angora whence retreating before more powerful hordes they advanced to the Lena where in their turn they dispossessed the weaker tribes which they found in possession of the country.
Considering the language connection, and the use of the term nationalities indicating something more widespread than a single tribe, I would conclude the term was indicating a Turkic peoples.
The Russian Wikipedia article for Turkic languages is titled Тюркские языки (t-iu-r-k-s-k-i-ie ...), which imho makes it very likely that Tiursk should be read as Turk or Turkic. If you can accept that с and к being out of sequence (or one к missing) is just a clerical error.
The center of the first Turkic state was east of the Khangai mountains, which is something like 500 kilometers south of the Sayan mountains and lake Baikal. Don't get fooled by the large djstance between lake Baikal and the modern state of Turkey!
"Irghana-Kon" mentioned in the cited Overland to China is actually the mythical Ergenekon. And so "Tiursk tribe" should probably refer to Turkic peoples.
