This murderous assault on Mr. Sumner cannot be considered as having strengthened the political position of the slave power. It was a great mistake in itself, and it was a greater mistake in being indorsed by such multitudes in the slave States. In thus taking the responsibility of the act, they fully admitted that brutality, violence, and cowardly attempts at assassination are natural characteristics of slavery. A thrill of horror went through the civilized world on this occasion. All the free States felt themselves outraged. That an attempt should be made to kill in his seat a Northern man, for words spoken in debate, was a gross insult and wrong to the nation, and deepened everywhere the detestation felt for the system. But madness must have its perfect work. One more step remained to be taken by the slave power, and that was to claim the right, under the Constitution, and protected by the general government, to carry slaves and slavery into all the Territories. It was not enough that they were not prohibited by acts of Congress. They must not allow the people of the Territories to decide for themselves whether slavery should exist among them or not. It had a right to exist there, in spite of the people. A single man from South Carolina, going with his slaves into Nebraska, should have the power of making that a slave State, though all the rest of its inhabitants wished it to be free. And if he were troubled by his neighbors, he had a right to call on the military power of the United States to protect him against them. Such was the doctrine of the Dred Scott case, such the doctrine accepted by the majority of the United States Senate under the lead of Jefferson Davis in the spring of 1859. Such was the doctrine demanded by the Southern members of the Democratic Convention in Charleston, S. C., in May, 1860, and, failing to carry it, they broke up that convention. And it was because they were defeated in this purpose of carrying slavery into the Territories that they seceded from the Union, and formed the Southern Confederacy.