Note 1 — Chapter VIII · THE OBI.

The principal branch of the Obi is the Irtish, which, rising in Mongolia, passes through Lake Zaizang, about 1,720 feet above the sea level. It then passes Ustkammenogorsk, in the Altai region, where it becomes navigable, and, flowing on to Omsk, is subsequently joined by the Ishim and the Tobol, which last is made up of the Isset, Tura, and Tavda, the last three descending from the watershed of the Urals. The Obi proper rises in Siberia, and runs with a rapid course through the northern ridges of the Altai mountains, amid scenery resembling in beauty and grandeur that of the Lake of Lucerne. It is joined north of Tomsk by the Tom and the Tchulim, and then it flows on in a westerly course, swelled by many minor streams, to its junction with the Irtish, on the 60th parallel. Before reaching the Tom the current becomes gentle, and allows of easy navigation, especially in spring, when water is abundant; but, in approaching the Irtish, shoals become numerous. The Obi then takes a northerly course, and frequently divides as it traverses an alluvial and low plain from 40 to 50 miles wide, the greater part of which, after winter, is inundated. This enormous river, having now a course of 2,700 miles, falls into the Obi Gulf, which is 400 miles long, and from 70 to 80 miles wide. For a large part of the year the water flows under ice, which at Tiumen is from 3 to 4 feet, and on the gulf is 7 feet, thick.