rule of law other than that relating to consideration, are sufficient consideration for one another. It remains only to consider two special cases which have been thought difficult to reconcile with the theory of consideration which I have advanced. As has been said, it is undoubtedly law that a voidable or unenforceable promise is sufficient consideration to support a counter-promise. One may state the result of the cases on this question clearly. A defense given by law to a promisor enabling him at his option to avoid performance, will not prevent the promise from being sufficient consideration. I believe that this rule, though wise, must be regarded as an exception to the principles of consideration. The promise of an infant, an insane person, or one whose promise is for any reason performable only at his option, is not a thing of such value, whatever may be the nature of the thing promised, that the law would ordinarily regard such a promise as sufficient consideration. This may be readily seen by supposing that the terms of a voidable obligation such as the law imposes on promisors of the classes just enumerated, be put in words and then made as a promise by an adult under no disability. It will be obvious that the promise is insufficient to support a counter-promise. Whether the infant's promise be translated as meaning — I promise to perform if I choose, or I promise to perform if I conclude to ratify, or I promise to perform unless I choose to avoid my agreement, it is clear that the promise is illusory, since its performance is by its very terms at the option of the promisor, and he can exercise this option without incurring a detriment or giving a benefit. The same line of argument is applicable to any voidable or unenforceable promise. That a promise which in terms reservet the option of performance to the promisor is insufficient suppors of counter-promise is well settled.62 And the promise is no more effectual because the condition contained in it is in the form of a condition subsequent rather than a condition precedent. An agreement which one party reserves the right to cancel at his pleasure, cannot create a contract. These cases where promises 62 Roberts v. Smith, 4 H. & N. 315 (1859); Montreal Gas Co. v. Vasey, [1900] A. C. 595; Oakland Motor Car Co. v. Indiana Automobile Co., 201 Fed. 499 (1912); Velie Motor Car Co. v. Kopmeier Motor Co., 194 Fed. 324; Vogel v. Pekoc, 157 Ill. 339, 42 N. E. 386 (1895); Lydick v. Baltimore & Ohio R. Co., 17 W. Va. 427 (1880). are held sufficient consideration though the law gives the promisor an unqualified right to avoid them, can be satisfactorily explained on no theory of consideration except that advanced by Professor Ames that any promise asked for if in fact given is sufficient consideration. And though Professor Ames's theory escapes this difficulty, it is not the theory upon which these cases were actually decided, and, as has been seen, involves such other difficulties when compared with existing law that it cannot be accepted. Cases where a promisor warrants the truth of existing facts have also been put in opposition to the argument that a promise must in order to furnish sufficient consideration be a promise of something which would if actually given be sufficient consideration for a unilateral contract. It is said: "I agree that a horse which I sell shall be sound, or shall win a race; or that a man shall pay his debts; or that a ship shall come safe to port: in all these cases my promise is a valid consideration for a counterpromise. Yet the soundness or speed of the horse, the solvency of the third party, or the safety of the ship could not be a valid consideration for a promise made to me." 63 Here, however, there is no inconsistency or exception. A warranty or promise of the truth of an existing fact can only be understood as meaning a promise to be responsible in damages if the fact asserted is not true. The warranty of the existence of an event in the future when construed means either a promise to bring about the existence of the event or a promise to pay damages if the event does not happen, and either the present causation of the fact or the present payment of damages 64 for the unsoundness or lack of speed of the horse, the insolvency of the third party, or the loss of the ship would be as sufficient consideration as the promise of warranty. HARVARD LAW SCHOOL. 63 Professor Beale, 17 HARV. L. REV. 82. Samuel Williston. 64 See Holmes, Common Law, 299. The distinguished author's extension of this construction to all contracts seems erroneous. It is merely a question of fact whether a promisor agrees to take the risk" of an event happening (that is to pay for the consequences if it does not happen) or agrees to cause it to happen. 66 THEORIES OF WATER LAW. LIKE other things of general concern, water has been the subject of much legal thought, and different theories have been worked out. It appears therefrom that possible theories of water law take form according to certain underlying ideas. In this paper I will compare these ideas and the systems which grow out of them. Existing or proposed systems of water law have one first elemental principle for all of them. In the beginning they have the same root in their attitude to running water as a physical substance. It is the idea that water running in streams and watercourses is not of itself the property of any person and cannot be. Although differing with regard to the regulation of the use of the water, yet the water itself, by all of them, and by probably all people, is considered not to belong to any person. This is expressed at the beginning by the Roman jurists, in the compilation of Justinian, as follows: "By natural law these things are common to all: the air, running water, the sea, and as a consequence the shores of the sea." In the same class are placed the wild animals of the forest, fish in the sea, gems on the seashore, the sea-water, rain and so on. They are under no man's domain in their wild state, and hence can be no man's property while in their original condition. In the terms of logic, they are "outside of the universe of discourse" when property is mentioned. They are not property, or, as has been said, they are in the "negative community." This is sometimes phrased that they "belong to the public" or to the "state in trust for the people." The Civil Code of California, § 1410, now uses the expression that waters "are the property of the people of the state.” But for present purposes I only want to point out that all systems of water law adopt the elemental idea that running water while in its natural situation is not owned; that the law regulates the use of it, but that rights of flow and use are what the law recognizes, and not property in the water itself. The water itself is "common" or "publici juris." This is accepted to-day by courts, legislatures, and publicists alike. In the follow ing discussion I will use the phrase that running water is "common to all." Developing from this foundation are certain possible systems of water law. The first which I will consider is what appears, at first glance, the most natural one; that is, the rule whereby everyone, like the beasts in the forest or the Indians on the plains, may take out freely from springs and streams what he wants, and that the first so to do shall have a prior right to continue to do so. This law of "Prior Appropriation," as it is called, is the chief law in the states west of the Mississippi Valley. It had its beginning in the early days of the state of California, when the region was an uninhabited frontier presenting a condition close to the primitive condition of the wild animals in the forest and the Indians on the plains. It was all an unowned, unclaimed and unguarded wilderness of vast extent, where everything was new and theretofore no rights existed. The California miners diverted streams from one locality in the wilderness where there was no mining to another locality where there was mining, and used the water for washing out the gold and for supplying the purposes of mining camps. From California it spread to other frontier regions, such as Nevada, Oregon, Idaho, Utah and so on, and came into application as the earliest system of water law in the West in any of these states. Under this system the idea of a water-right was an idea of having possession of a portion of the flow of the stream. It was to protect the first possessor. It was called a possessory right and had the features of a possessory system. It was initiated by taking possession of a portion of the flow of the stream (that is, by diverting and carrying it to the place of intended use). The measure of right was the capacity of the ditch, as that measured the portion of flow taken into possession and for which his continuance in possession was to be protected. The point of diversion could be shifted up or down the stream, and was not fixed at any place. Nor could it be lost by non-use alone without relinquishment of the possession; the law allowed him to do what he willed with his own, and therefore he could abandon his possession if he chose, but it rested upon his own wishes in the matter, so long as he held possession. The foundation was his right to be protected in his possession simply because he came there first. Subsequent years have been more careful in conditioning possession upon beneficial use, making actual use rather than capacity of the ditch the measure of it, and the place of use a permanent condition of it, and non-use a self-sufficient cause of loss of it. Still, so long as he continues his use, the prior appropriator has the better right to-day under this system and must have where it prevails. Priority is still the foundation of it. It is based upon the idea that water titles must be secure and certain. The system is secure and certain for the prior appropriator, and, while it gives much less security to the subsequent one, certainty in one respect is given to him also, namely, the certainty that he will get nothing until the prior rights are fed. The system is eminently a pioneering system. It developed California and neighboring states, and is developing Canada and Australia, where it is also in force. The pioneer gambles for high stakes, and if the rewards are limited he won't begin the game and put much money in it. The law has said to the pioneer, “Go take the water and make the farms fruitful and develop the mines and the water powers, and you shall always have the first right in the stream." He has accepted the offer, invested his capital, planted his land and is reaping his harvest. When, however, full appropriation has been reached, priority diminishes the number of uses thereafter. The days of the pioneer have gone very largely — certainly the days of the individual pioneer with small-scale operations. Pioneering to-day is done more with the capital of New York, London and Paris than by frontiers-men with pick and shovel for their own private account. When, fifty years ago, a man appropriated water for his farm, from a stream of any considerable size, he left a surplus in the stream for others to appropriate; but to-day there are hundreds of appropriators on the most considerable sources of supply, and when another comes along on such streams he threatens the security of those who have gone before. This is already a common situation upon many western streams. I do not in this refer merely to the notices of appropriation of which so much has been said in the press. Those notices plaster the streams of California and probably throughout the West from source to mouth, and are mostly lapsed long ago. I refer by "appropriation" to actual diversions now in actual use, and this actual use, say the courts of a number of |