Beginning at a point in the middle of the main channel of the Missouri River, where the prolongation north of the range line between ranges two and three, east, would intersect the same; thence south with the said range line to the southeast corner of township forty-three, range two, east; thence in a direct line to a point sixteen chains north of the quarter-section corner on the line between sections fourteen and fifteen, in township forty, range two, east, it being the northeast corner of Washington County; thence due west to the middle of range four, west; thence north with the subdivisional lines to a point in the middle of the main channel of the Missouri River; thence down said river, in the middle of the main channel thereof as now located to the place of beginning.