This section is from the book "The National Capitol. Its Architecture Art And History", by George C. Hazelton, Jr. Also available from Amazon: The National Capitol Its Architecture Art and History.
The marble room is directly east of the President's room, and also opens upon the private lobby of the Senate. This room is built almost entirely of marble; the ceiling, pilasters and four fluted Corinthian columns of veined Italian marble, the walls and wainscoting of native dark-brown marble from Tennessee. It is used by the Senators as a private reception room. Persons who desire to see a Senator during a session, must first send their cards to him from the public reception room, which is on the east side of the chamber, and if the Senator grants an interview, the visitors are conducted to the marble room to await his coming.