The second, or upper, chamber of the US Congress, representing the 50 states of the union. The powers and composition of the Senate are set out in Article I of the US Constitution, and the Senate first met in 1789. Senators, two from each state, have six-year terms and were chosen by the state legislatures until 1913, when the Seventeenth Amendment provided for their direct election. The terms of one-third of the senators expire every two years. A senator must be at least 30 years old, must have been a US citizen for not less than nine years, and must be a resident of the state he or she represents. The Vice-President presides over the Senate, voting only in the case of a tie. The Senate must ratify all treaties, confirm important presidential appointments, and take a part in legislation. See also roman senate.