<P> The committee structure permits members of Congress to study a particular subject intensely . It is neither expected nor possible that a member be an expert on all subject areas before Congress . As time goes by, members develop expertise in particular subjects and their legal aspects . Committees investigate specialized subjects and advise the entire Congress about choices and trade - offs . The choice of specialty may be influenced by the member's constituency, important regional issues, prior background and experience . Senators often choose a different specialty from that of the other senator from their state to prevent overlap . Some committees specialize in running the business of other committees and exert a powerful influence over all legislation; for example, the House Ways and Means Committee has considerable influence over House affairs . </P> <P> Committees write legislation . While procedures such as the House discharge petition process can introduce bills to the House floor and effectively bypass committee input, they are exceedingly difficult to implement without committee action . Committees have power and have been called independent fiefdoms . Legislative, oversight, and internal administrative tasks are divided among about two hundred committees and subcommittees which gather information, evaluate alternatives, and identify problems . They propose solutions for consideration by the full chamber . In addition, they perform the function of oversight by monitoring the executive branch and investigating wrongdoing . </P> <P> At the start of each two - year session the House elects a speaker who does not normally preside over debates but serves as the majority party's leader . In the Senate, the Vice President is the ex officio president of the Senate . In addition, the Senate elects an officer called the President pro tempore . Pro tempore means for the time being and this office is usually held by the most senior member of the Senate's majority party and customarily keeps this position until there's a change in party control . Accordingly, the Senate does not necessarily elect a new president pro tempore at the beginning of a new Congress . In both the House and Senate, the actual presiding officer is generally a junior member of the majority party who is appointed so that new members become acquainted with the rules of the chamber . </P> <P> The Library of Congress was established by an act of Congress in 1800 . It is primarily housed in three buildings on Capitol Hill, but also includes several other sites: the National Library Service for the Blind and Physically Handicapped in Washington, D.C.; the National Audio - Visual Conservation Center in Culpeper, Virginia; a large book storage facility located at Ft . Meade, Maryland; and multiple overseas offices . The Library had mostly law books when it was burned by a British raiding party during the War of 1812, but the library's collections were restored and expanded when Congress authorized the purchase of Thomas Jefferson's private library . One of the Library's missions is to serve the Congress and its staff as well as the American public . It is the largest library in the world with nearly 150 million items including books, films, maps, photographs, music, manuscripts, graphics, and materials in 470 languages . </P>

Why did congress place the house and senate leaders at the top