After approaching its south-west extremity it abandons the broad valley which leads to the lake, and makes its way northwards through a narrow gap in the mountains and joins the Angara at Irkutsk.
Attempts are being made to render the Angara navigable below Irkutsk down to the Yenisei.
Surveys in Asiatic Russia are conducted by the topographical departments organized at Orenburg, Tashkent, Omsk, Irkutsk and Tiflis.
About Kansk in East Siberia they penetrate in the form of a broad gulf south-eastwards as far as Irkutsk.
They are named the Usinsk Mountains in West Sayan and the Tunka Alps in East Sayan; the latter, pierced by the Angara at Irkutsk, are in all probability continued north-east in the Baikal Mountains, which stretch from Irkutsk to Olkhon Island and the Svyatoi Nos peninsula of Lake Baikal, thus dividing the lake into two parts.?