Opportunities for administrative work, however, were scanty, and in 1864 Kropotkin accepted charge of a geographical survey expedition, crossing North Manchuria from Transbaikalia to the Amur, and shortly afterwards was attached to another expedition which proceeded up the Sungari River into the heart of Manchuria.
The boundary line which separates Mongolia from Manchuria runs past Dalai-nor and Lake Buir, crossing the Great Khingan in 47° 30' N., towards Tsit g ihar in Manchuria; then, crossing the Nonni river, it strikes the Sungari at Khulanchen, where it turns westwards up this river, reaching the Shara-muren river in 123° 30' E.
Below Chita, with Vladivostok, and sends off a branch from Kharbin, on the Sungari, to Dalny and Port Arthur.
Between the Nonni 'and the Sungari, and the rich plains of the Bureya and Silinji in the Amur province belong to this belt, 400 m.
East Siberia suffers less from this plague than the marshy Baraba steppe; but on the Amur and the Sungari large gnats are an intolerable plague.