Omt, or Obi, a river of Siberia, rises in the Altai Mountains, where it is formed by the union of two main streams, the Katunga and the Biya. It flows in an irregular course, but generally towards the N.W., till it joins the Irish from the south. It then turns northward, and flows in that direction, frequently dividing itself into two streams, which flow separately for long distances, and then unite again. It falls into the Gulf of Obe by three branches, the largest and deepest of which is that which lies to the east. Its whole length is estimated at 2000 miles. The principal affluents of the Obe are the Irish, which is longer than the branch which retains the name of Obe, the Tom, the Choelyn, and the Ket; while the Irish receives from the west the Tobol and the Iskim. Both the Irish and the Obe abound in fish, which might be made a valuable article of export. The country drained by the Obe and its tributaries is calculated to have an area of 1,370,000 square miles. The Gulf of Obe, which derives its name from the above river, is an inlet of the Arctic Ocean, between 70 and 80 miles in breadth, and upwards of 400 in length. It lies between N. Lat. 67° 30' and 72° 30'; E. Long. 72° and 77°.