_Monroe's Statement of the Doctrine._--Acting on the advice of trusted friends, President Monroe embodied in his message to Congress, on December 2, 1823, a statement of principles now famous throughout the world as the Monroe Doctrine. To the autocrats of Europe he announced that he would regard "any attempt on their part to extend their system to any portion of this hemisphere as dangerous to our peace and safety." While he did not propose to interfere with existing colonies dependent on European powers, he ranged himself squarely on the side of those that had declared their independence. Any attempt by a European power to oppress them or control their destiny in any manner he characterized as "a manifestation of an unfriendly disposition toward the United States." Referring in another part of his message to a recent claim which the Czar had made to the Pacific coast, President Monroe warned the Old World that "the American continents, by the free and independent condition which they have assumed and maintained, are henceforth not to be considered as subjects for future colonization by any European powers." The effect of this declaration was immediate and profound. Men whose political horizon had been limited to a community or state were led to consider their nation as a great power among the sovereignties of the earth, taking its part in shaping their international relations. =The Missouri Compromise.=--Respecting one other important measure of this period, the Republicans also took a broad view of their obligations under the Constitution; namely, the Missouri Compromise. It is true, they insisted on the admission of Missouri as a slave state, balanced against the free state of Maine; but at the same time they assented to the prohibition of slavery in the Louisiana territory north of the line 36 deg. 30'. During the debate on the subject an extreme view had been presented, to the effect that Congress had no constitutional warrant for abolishing slavery in the territories. The precedent of the Northwest Ordinance, ratified by Congress in 1789, seemed a conclusive answer from practice to this contention; but Monroe submitted the issue to his cabinet, which included Calhoun of South Carolina, Crawford of Georgia, and Wirt of Virginia, all presumably adherents to the Jeffersonian principle of strict construction. He received in reply a unanimous verdict to the effect that Congress did have the power to prohibit slavery in the territories governed by it. Acting on this advice he approved, on March 6, 1820, the bill establishing freedom north of the compromise line. This generous interpretation of the powers of Congress stood for nearly forty years, until repudiated by the Supreme Court in the Dred Scott case. THE NATIONAL DECISIONS OF CHIEF JUSTICE MARSHALL