Upper and Lower, two rivers of Asiatic Russia, in the government of Irkutsk. The former rises in the mountains of Nerchinsk, and after a westerly course of about 300 miles, falls into Lake Baikal. The latter has its rise in Lake Baikal, near its southern extremity, and passing the town of Irkutsk, falls into the Jenisei after a course of above 1100 miles, forming several waterfalls in its progress.