Correspondence of the Courier.WASHINGTON, MARCH 9.The Supreme Gourt of the IT. S. adjourned to-day. Mr Webster, delivereda great argument, and probably his best,before that Court, in the case of the boundary question between. Rhode Island and Massachusetts.T he decision ofthe Court.1 n die famous Ami stud case, was pronounced, to-day,by Justice Story- The judgment of th^jCourt was that the Negroes go free,There was no dissent to this judgment.front any member of the Court. [ TheGlobe states that Judge Baldwin dissented.] The basis ofthe decision was that the Negroes, though claimed asproperty under the treaty of 1795, with Spain, weare acuallv free, as Ifozat negroes, according to the laws of Spain and a certain treaty of Spain made with Great Britain.