The effort to obtain for the Senate the power to abrogate treaties had peculiar interest at this time, from the known desire of certain Senators to terminate the stipulation between the United States and Great Britain, requiring a naval force on the coast of Africa for the suppression of the slave-trade. In 1854 Mr. Slidell brought forward a proposition to this effect in Executive Session, assuming that the stipulation could be terminated by a simple vote of the Senate. Mr. Sumner insisted that the prerogative belonged to the law-making power, and could be exercised only by Act of Congress. By his effort the proposition was defeated. The power of the Senate over the abrogation of treaties was brought forward in Legislative Session, on the motion of Mr. Sumner, in connection with the Danish Sound dues, being the tax at Elsinore laid by Denmark upon the cargoes of vessels passing through the Sound into and out from the Baltic Sea. In 1841, Mr. Webster, as Secretary of State, traced the origin of this tax to the treaty of 1645 between Denmark and Holland, embracing a tariff of the principal articles then known in commerce; which treaty was the basis of our own concluded with Denmark in 1826, and limited to continue ten years from date, and further until the end of one year after notice by either party of an intention to terminate it; but he contented himself with recommending friendly negotiations, “with a view of securing to the commerce of the United States a full participation in any reduction of these duties, or the benefits resulting from any new arrangements respecting them which may be granted to the commerce of other states.”[47] In 1848, Mr. Buchanan, as Secretary of State, instructed our Minister at Copenhagen, that, “under the public law of nations, it cannot be pretended that Denmark has any right to levy duties on vessels passing through the Sound from the North Sea to the Baltic.” President Pierce, in his annual message of 1854, proposed to terminate the treaty of 1826; the Senate, by simple resolution in Executive Session, March 3, 1855, undertook to terminate it; and the President, in his annual message of 1855, announced that the proper notice had been given to Denmark.[48] Mr. Sumner, impressed with the conviction that this notice was a bad precedent, and in the interest of the Slave Power, which controlled the Senate, besides being inadequate under the Constitution, brought forward the following resolution:--