Entering by either of the doors at the head of the staircase, the visitor at once steps out upon an embayed gallery, affording a spacious and uninterrupted view of the great domed Reading Room, or Rotunda, which, in every sense, is the central and most important portion of the Library. As such, it is marked by a magnificence of architecture and decoration nowhere else to be found in the building. Outside, from whatever direction one approaches, the gilded dome which forms its outer shell is the first thing to catch the eye; and the golden flame of the torch which surmounts the lantern indicates to the passer-by at once the central and the highest point of the whole structure. Within, richer materials have been used, and decoration has been more freely employed than in any other part of the Library. Sculpture and paintings, rare marbles, and a broad scheme of color and of ornamentation in stucco relief unite with a lofty architectural design to form what is one of the most notable interiors in the country. =The Importance of the Rotunda.=--The detailed description of the Rotunda may be deferred a little, however, in order to explain its relation to the rest of the building, and, especially, the reason for its central position. Besides accumulating books and providing the student with proper accommodations for his work--such as good light and convenient chairs and tables--it is the business of every well managed library to supply its readers with the books they desire in the shortest possible time and with the least possible amount of friction. A well digested catalogue is the first requisite; the second is that the books should be stored in a place as closely accessible to the reading room as may be. In a small library this is a simple matter; the same room will be sufficient for both books and readers. When the number of volumes increases it is necessary to shelve them in a compact system of bookcases called a “stack”--or, as in the Library of Congress, in a series of stacks--which must occupy a portion of the building by itself. The reading room and the stacks being thus separated, it is still the aim of the architect to place them in such a way as to retain as far as possible the practical convenience of the smaller library, where every reader is almost within reaching distance of every book. This end is most easily attained by adopting what is called the “central system” of library construction, which is the system followed in the Library of Congress. It has already been seen that the building is in the form of a cross enclosed within a rectangle, thus allowing space for four courts for light and air. At the intersections of the arms of the cross is the Rotunda, the main entrance to which is through the west arm of the cross. The other three arms are occupied by the stacks; the East Stack, directly opposite, is the second short arm; the North and South Stacks, each the same length, are the two long arms. It