or OB, a large and famous river of Asiatic Russia, which issues from the Altin lake (called by the Russians Teliskoi Ozero), in latitude 52 degrees, and longitude 103 degrees 30 minutes. Its name signifies Great; and accordingly in Russia it is often styled the Great River. The Calmucks and Tartars call it Umar. Its stream is very large and smooth, its current being usually slow; and it is in general between two and three hundred fathoms broad; though in some places it is much wider. It affords plenty of fish, and is navigable almost to the lake from which it springs. After a long winding course through a vast tract of land, in which it forms several islands, it empties itself in latitude 67 degrees, and longitude 86 degrees, into a bay, which, extending near 400 miles farther, joins the Icy sea, in latitude 73. 39. and longitude 90. The springs from which this river rises, are not very copious: but it receives in its course the waters of a great number of considerable streams. Of these, the Tom and the Irtis are the most considerable: the Tom falls into it in latitude 58. and the Irtis in latitude 61. and longitude 86. The exact course of this river was unknown till the country was surveyed by the Russians; who have given us tolerable maps of it and of all Siberia. The Oby forms the boundary between Europe and Asia, and its course is upwards of 2000 miles in length.