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The Green Bag

tions of England, Portugal and other countries were allowed to apse. Sovereignty in the light of these con siderations might be described as the measure of the state's interest in a terri tory, or domain, and I believe that from the philosophic point of view the de scription will meet the test of application. The high sea, then, is extra-sovereign because the state's interests upon it are too tenuous to make it worth while for sovereign power to attempt to stretch its might that far. What is the result when this test is applied to the air? The entire art of aviation is based upon physical or mechanical principles. It is in no sense due to primarily natural causes. The balloon floats because of the physical fact that certain gases at a certain temperature and in sufficient quantity are light enough to maintain themselves in air and carry besides a weight proportionate to the difference between their density and that of the air. The aeroplane depends upon its power, which is strong enough to create a counter-wind capable of sustaining its weight. The aeroplane travels fast enough for its weight to be distributed over a body of air that as a whole is dense enough to sustain it. Or, to ex plain it in a different way, the aeroplane at a given thousandth of a second is supported by a column of air extending from its lower surface to the ground That single column is not dense enough to poise it, and if the machine suddenly stopped dead, it would fall straight down, although provided with its guiding apparatus and planes specially designed to get from the air all the lift there is in them. An aeroplane flies because it moves fast enough through the air for it to be supported, not by a single col umn, but by many such within the space necessary for gravity to get in an effec tive pull downward. The principles of

sustentation, particularly through de veloping the aerodynamics of the en trant edge, may be much better under stood in time, but the ultimate desire of soaring flight is too remote a pos sibility to build any legal system upon. Soaring flight is the counterpart in the air of seaworthiness. A seaworthy craft remains floating in its element of water by the operation of the law of nature, which decrees that water is heavier than the thing which displaces it. Such a craft needs power of sail or motor only to move from place to place. The craft can stand still in water. No humanly constructed machine can per manently remain at rest in the air. . Birds accomplish soaring flight by alter ing the position of their wings and so forcing the wind under them in such a manner that it carries them whither they will. Rigidity is an essential of an aeroplane, and so far as we can see will always be a primary feature of it. The balloon, while capable of greater sustentation, still gives no promise of remaining in the air for long periods, and it seems far too much to hope that it can be so directed to land where it wishes, except under very favorable conditions. Nor does it give promise of ability to weather out a storm in its own element, a thing any seaworthy craft with half a chance will do. The important distinction between the sustentation of sea and aircraft just set forth would lose its significance were it not for the position of the air in which balloon and aeroplane travel. The sea is at the side of the land where men dwell, and nothing that can occur upon it has any concern for the land, except as the loss of persons or cargo or damage to the craft itself affects individuals on land. With these exceptions, every thing that happens at sea is as far re moved in respect of interest from the