In America this theory has been actually put in practice; and the supreme court of the United States is the sole tribunal of the nation. Its power extends to all the cases arising under laws and treaties made by the executive and legislative authorities, to all cases of admiralty and maritime jurisdiction, and in general to all points which affect the law of nations. It may even be affirmed that, although its constitution is essentially judicial, its prerogatives are almost entirely political. Its sole object is to enforce the execution of the laws of the Union; and the Union only regulates the relations of the government with the citizens, and of the nation with foreign powers: the relations of citizens among themselves are almost exclusively regulated by the sovereignty of the states. A second and still greater cause of the preponderance of this court may be adduced. In the nations of Europe the courts of justice are only called upon to try the controversies of private individuals; but the supreme court of the United States summons sovereign powers to its bar. When the clerk of the court advances on the steps of the tribunal, and simply says, "The state of New York _versus_ the state of Ohio," it is impossible not to feel that the court which he addresses is no ordinary body; and when it is recollected that one of these parties represents one million, and the other two millions of men, one is struck by the responsibility of the seven judges whose decision is about to satisfy or to disappoint so large a number of their fellow-citizens. The peace, the prosperity, and the very existence of the Union, are invested in the hands of the seven judges. Without their active co-operation the constitution would be a dead letter: the executive appeals to them for assistance against the encroachments of the legislative powers; the legislature demands their protection from the designs of the executive; they defend the Union from the disobedience of the states, the states from the exaggerated claims of the Union, the public interest against the interests of private citizens, and the conservative spirit of order against the fleeting innovations of democracy. Their power is enormous, but it is clothed in the authority of public opinion. They are the all-powerful guardians of a people which respects law; but they would be impotent against popular neglect or popular contempt. The force of public opinion is the most intractable of agents, because its exact limits cannot be defined; and it is not less dangerous to exceed, than to remain below the boundary prescribed.