On consideration of the report of the commissioners, heretofore selected to run, locate and mark portions of the boundary between the States of Texas and Oklahoma along the south bank of the Red River, showing that they have run, located and marked the portion of such boundary along the Big Bend Area, such report being as follows:
"To the Chief Justice and the Associate Justices of the Supreme Court of the United States:
"As commissioners designated in the decree of March 12, 1923, in the above entitled cause, we have run, located and marked upon the ground the boundary between the
States of Texas and Oklahoma along the Red River in what is known as the Big Bend Area (Area 'A') in accordance with that decree and the principles announced in the opinion delivered January 15, 1923, and we have the honor to submit the following joint report respecting that part of our work, with field notes and maps.
"Paragraphs 5, 6 and 7 of the decree follow:
"'5. The south bank of the river is the water-washed and relatively permanent elevation or acclivity, commonly called a cut bank, along the southerly side of the river which separates its bed from the adjacent upland, whether valley or hill, and usually serves to confine the waters within the bed and to preserve the course of the river.
"'6. The boundary between the two States is on and along that bank at the mean level attained by the waters of the river when they reach and wash the bank without overflowing it.
"'7. At exceptional places where there is no well defined cut bank, but only a gradual incline from the sand bed of the river to the upland, the boundary is a line over such incline conforming to the mean level of the waters when at other places in that vicinity they reach and wash the cut bank without overflowing it.'
"The foregoing specifications applied in the light of the opinion, admit of, and require the exercise of practical judgment in determining the line intended; but certain fundamentals, such as the following, obviously must form the final basis for the exact location of the line.
"The boundary line is a gradient of the flowing water in the river. It is located midway between the lower level of the flowing water that just reaches the cut bank, and the higher level of it that just does not overtop the cut bank. The physical top of the cut bank being very uneven in profile, cannot be a datum for locating the boundary line; but a gradient along the bank must be
used for that purpose. The highest point on this gradient must not be higher than the lowest acceptable point on the bank in that vicinity. The ...