Beginning in the middle of the main channel of the Missouri River, at a point where the prolongation north of the range line between ranges twenty-three and twenty-four would intersect the same; thence due south with said range line to the southwest corner of section eighteen, township forty-eight, range twenty-three; thence east with the subdivisional lines to the southeast corner of section thirteen, township forty-eight, range twenty; thence north with the range line between ranges nineteen and twenty to the northeast corner of township forty-eight, range twenty; thence in a direct line to a point on the Missouri River where the range line between ranges eighteen and nineteen crosses said river in township fifty; thence north to the middle of the main channel of the Missouri river; thence up said river, in the middle of the main channel thereof, to the place of beginning.