successively brought into use to meet the demands of increasing population and wealth. (Cited also in Western Union Telegraph Co. v. State of Texas, 105 U. S., 460.)

The power of Congress would similarly extend to aerial navigation.

Mr. Justice Holmes (1908) says of the development of the idea of demarcation between public and private rights in the atmosphere, water, etc.

All rights tend to declare themselves absolute to their logical extreme. Yet all in fact are limited by the neighborhood of principles of policy which are other than those on which the particular right is founded, and which become strong enough to hold their own when a certain point is reached. The limits set to property by other public interests present themselves as a branch of what is called the police power of the State. The boundary at which the conflicting interests balance can not be determined by any general formula in advance, but points in the line, or helping to establish it, are fixed by decisions that this or that concrete case falls on the nearer or farther side. For instance, the police power may limit the height of buildings, in a city, without compensation. To that extent it cuts down what otherwise would be the rights of property. But if it should attempt to limit the height so far as to make an ordinary building lot wholly useless, the rights of property would prevail over the other public interest, and the police power would fail. To set such a limit would need compensation and the power of eminent domain.

It sometimes is difficult to fix boundary stones between the private right of property and the police power when, as in the case at bar, we know of few decisions that are very much in point. But it is recognized that the State as quasi-sovereign and representative of the interests of the public has a standing in court to protect the atmosphere, the water, and the forests within its territory, irrespective of the assent or dissent of the private owners of the land most immediately concerned. son Water Co. v. McCarter, 209 U. S., 349.)

Mr. Justice Holmes also in 1907 said:

(Hud

It is a fair and reasonable demand on the part of a sovereign that the air over its territory should not be polluted on a great scale by sulphurous acid gas, that the forests on its mountains, be they better or worse, and whatever domestic destruction they have suffered, should not be further destroyed or threatened by the act of persons beyond its control, that the crops and orchards on its hills should not be endangered from the same

source.

Mr. Justice Holmes also affirms that a commonwealth of the United States

has an interest independent of and behind the titles of its citizens, in all the earth and air within its domain. It has the last word as to whether its mountains shall be stripped of their forests, and its inhabitants shall breathe pure air. (Georgia v. Tennessee Copper Co., 206 U. S., 230.)

Belligerent air craft in neutral territory.-Situation II (a) gives rise to the question of the rights of air craft of belligerents when in neutral territory.

Belligerent State X, brings a balloon to neutral State Z, and fills it with gas preparatory to a flight with view to destroying a part of the fleet of its enemy, State Y, by dropping explosives from above.

If the balloon is permitted to take in the gas, will it be an act of the nature which is permitted to vessels engaged in maritime war when they are permitted to coal in neutral territory? The subject of rights of coaling in neutral ports was given full consideration in 1910, International Law Situations, Situation I, pages 9-44. Previous to the Hague Convention respecting the Rights and Duties of Neutral Powers in Maritime War, there was a growing tendency to restrict the amount of coal that might be taken in a neutral port. By article 19 of that convention, the neutral State was left the option of limiting the supply to an amount necessary to reach "the nearest home port or some nearer named neutral destination" or the neutral might permit the vessels "to take fuel necessary to fill their bunkers." Those who maintain the doctrine of an unlimited supply of fuel regard fuel simply as one form of supplies which makes navigation possible. Those who would restrict the supply regard fuel as more in the nature of war supplies. The drift of opinion as shown by The Hague regulations is toward the allowing of freedom in taking on fuel in a neutral port when not oftener than once in three months.

Even with this extension of the right of coaling, the entrance of a balloon into neutral territory may be in marked contrast to the entrance of a vessel of war into

a neutral port. One belligerent may easily learn of the entrance of a vessel of his enemy to a neutral port. The course which the vessel will follow on departure, the time of sojourn, and other facts may be reasonably determined. A vessel in a neutral port must ordinarily put to sea before reaching a home or an enemy port. A belligerent would ordinarily, therefore, have an opportunity to meet and to engage the vessel of his opponent in an area where battle is lawful and without material risk to the neutral.

It is possible, however, that the territory of States might be so situated that a neutral State might be directly between the two belligerents; e. g., if war existed between Germany and Spain. In such a case would the bringing of a war balloon to the French frontier from Germany place France under any obligation to permit the balloon to enter and take the necessary gas to make it navigable? If German balloons were permitted to enter French territory, take gas, and from points of advantage attack Spanish forces and territory, would such permission by France be analogous to the entrance of German troops, or would it be the use of French territory as a base? Whether or not the right of absolute sovereignty in the air is in the subjacent State, certainly France would be under no obligation to receive a German war balloon into its territory when France is neutral except on ground of humanity or vis major. France could scarcely permit German war balloons to use French territory as a point from which to attack Spain, and if German forces should enter French territory internment would be the penalty.

If, however, a war balloon were brought into a French port on board a German cruiser or other German public vessel, would it not be entitled to the exemptions to which the boats, launches, etc., of such vessels are entitled, and would it receive such treatment so long as it is appurtenant to the vessel? Undoubtedly the vessel would be allowed to take coal, oil, or other fuel for navigation; the launches would have similar privileges. Would the tak

ing of gas by an air craft appurtenant to the public ship be analogous?

When the air craft appertains to the land forces The Hague Convention respecting the Rights and Duties of Neutral Powers and Persons in Case of War on Land, 1907, would prevail. Article 2 provides that:

Belligerents are forbidden to move troops or convoys of either munitions of war or supplies across the territory of a neutral power.

Article 2 of the same convention provides for internment of troops entering neutral territory.

When the air craft belongs to the naval forces and comes into port under its own power, it may probably be allowed to take on supplies analogous to the supply of fuel for war vessels without violation of any neutral obligation. The taking of coal is often with a view to bringing the war vessel within range of the enemy. The taking of gas by a balloon might be for a similar purpose. The neutral has full right to regulate the taking of coal, as has been shown in recent wars. The neutral would have a similar right to regulate the supply of gas.

In the use of neutral land for balloons for land warfare the neutral territory becomes practically a base, and the neutral power is in reality receiving the belligerent forces into its territory, which is, according to the Convention respecting the Rights and Duties of Neutral Powers and Persons in Case of War on Land, Article 2, prohibited, unless internment follows.

An air craft of a belligerent that is brought, on board a war vessel, into the territorial waters of a neutral may or may not be fitted for use in war. If at the time it is not fitted for use and the neutral State allows it to make the preparations necessary to adapt it for war the State will doubtless be liable to the suspicion that its territory has been used as a base for warlike preparations.

Review of Situation II (a).-In the situation as stated the balloon is brought to neutral State Z to be filled with gas with view to a flight in order to destroy a part of the fleet of Y. This would seem to be an act in the nature

of the use of the territory of State Z as a base for warlike operations and should be forbidden.

Solution (a). The protest of belligerent State Y should be heeded by neutral State Z.

Firing into neutral territory.-In Situation II (b), the question is raised as to what could be done if the forces of one belligerent, State X, so maneuvers a balloon that if shot at by the forces of the other belligerent, State Y, the shot will fall in the jurisdiction of neutral State B.

Unquestionably Y has a right to fire at a war balloon of State X. At the same time State B may demand that its jurisdiction be not violated.

The Hague Convention respecting the Rights and Duties of Neutral Powers and Persons in Case of War on Land of 1907 provides, in article 1, "The territory of neutral powers is inviolable." The firing of a shot which would land in neutral territory would be a violation of neutrality and the neutral might, without offense, proceed against the party committing such violation.

That the hostilities are in such neighborhood that the risk of firing into a neutral State is present does not in any way excuse the belligerent from guarding against such action.

Solution (b).-Y may take any action which would not involve a violation of neutral jurisdiction, as would be the case if the projectile should fall in the territory of State B.

Jurisdiction over neutral air craft.—It is evident from Situation II (c) that there may be a risk to a belligerent from the flight of a neutral air craft over belligerent territory. If the jurisdiction of the air space is not in the subjacent State, the belligerent's right to control the use of the air space in the time of war would be limited. It would seem that such a claim would lead to many unfortunate complications. On the other hand, if the belligerent has jurisdiction over the air space above the territory, the Government can prescribe regulations for its use. Whether the theory that the air is free or the