Beginning in the middle of the main channel of the Missouri River, where a prolongation south of the range line between ranges thirty-six and thirty-seven would intersect the same; thence north with said line to the middle of the main channel of the Nodaway River; thence following the middle of Nodaway River up north, until it strikes the subdivision line dividing into two equal parts township sixty-three; thence west on said line to the middle of the main channel of the Missouri River; thence down said river, in the middle of the main channel thereof, to the place of beginning.