Beginning at a point in the middle of the main channel of the Mississippi River, where the prolongation east of the township line between townships fifty-nine and sixty would intersect the same; thence west on said township line to the southwest corner of township sixty, range nine, west; thence north with the range line between ranges nine and ten, west, to the northwest corner of section nineteen, township sixty-three, range nine, west; thence east with the subdivisional lines to the middle of the main channel of the Mississippi River; thence down the said river, in the middle of the main channel thereof, to the place of beginning.