=251. Discussion of the Difficulties.=—These various difficulties taxed all the faculties of the members. It sometimes seemed that not another step of progress could be made, and that the delegates would be obliged to abandon the task and go home. As discussion advanced, it became evident that no agreement could be made except through a general spirit of conciliation and compromise. The convention sat with closed doors, and for four months considered the stupendous difficulties that confronted them. At length, on the 17th day of September, 1787, they agreed upon a constitution and adjourned. It was to go into effect when ratified by the conventions of nine states. =252. Four Great Lines of Compromise.=—The Constitution was built upon a basis of four great lines of mutual concession. First, the smaller states were brought to agreement by being allowed the same representation in the Senate as the larger states; while the larger states were satisfied by being allowed to send to the House of Representatives a number of delegates to be determined by the number of inhabitants. Second, the question of the representation of slavery in Congress was finally adjusted by providing that for determining the number of representatives of each state, Congress should add to the number of freemen three-fifths of all persons held to service. Congress was also prohibited from abolishing the foreign slave trade before 1808. Third, the advocates of a strong central government came to an agreement with the advocates of a weak one by allowing the dividing line between the authority of the central government and of the several states to be somewhat vaguely defined, and by leaving such definition to the course of future events. It is probable that if either side had insisted on putting into words a statement authorizing its interpretation, no agreement could have been reached. This uncertainty of interpretation, though apparently necessary to an agreement on the Constitution, might be called the fundamental cause of the Civil War in 1861. Fourth, while the President, by being made commander in chief of the army and being intrusted with the enforcement of all laws, was given great authority, he was put under rigid constitutional checks in numerous ways. In case he should exceed his authority, he could be impeached by the House of Representatives and tried by the Senate; and in case of conviction, removed from office. It was further provided that in all cases whatsoever involving differences of opinion regarding the Constitution, the Supreme Court should render authoritative decision. This authority of the Supreme Court was the most marked peculiarity of the Constitution. [Illustration: FEDERAL HALL, NEW YORK CITY.]