“It may be imagined that a nuisance might be created by a State upon a navigable river like the Danube which would amount to a _casus belli_ for a State lower down unless removed. If such a nuisance were created by a State upon the Mississippi, the controversy would be resolved by the more peaceful means of a suit in this Court.” Speaking of this provision in the Constitution extending the judicial power to controversies between States, Mr. Justice Bradley in Hans vs. Louisiana (134 U.S. 1-15) said: “Some things, undoubtedly, were made justiciable which were not known as such at the common law; such, for example, as controversies between States as to boundary lines, and other questions admitting of judicial solution. And yet the case of Penn vs. Lord Baltimore (I Ves. Sen. 444) shows that some of these unusual subjects of litigation were not unknown to the courts even in Colonial times; and several cases of the same general character arose under the Articles of Confederation, and were brought before the tribunal provided for that purpose in those articles (131 U. S. App. 1). The establishment of this new branch of jurisdiction seemed to be necessary from the extinguishment of diplomatic relations between the States. Of other controversies between a State and another State, or its citizens, which, on the settled principles of public law, are not subjects of judicial cognizance, this Court has often declined to take jurisdiction.” A very satisfactory discussion of the scope of the power of the Supreme Court to settle controversies between States is contained in Mr. Justice Brewer’s opinion in the suit brought by Kansas against Colorado to restrain the latter from absorbing so much of the water of the Arkansas River flowing from Colorado into Kansas as seriously to interfere with the supply of water from the river for irrigation purposes in Kansas. He said (206 U. S. 95, 99):