=Connection with the Capitol.=--It is calculated that, by means of the pneumatic tubes and the book-carrying apparatus, it will require no more than six or seven minutes to bring a book from the stacks, from the time it is first called for. Valuable, however, as is the use of machinery in connecting widely distant portions of the Library, it is even more important as a factor in bringing together the Library itself and the Capitol, where hardly an hour passes, during a session of Congress, but some member desires to draw books for immediate use in debate or committee work. The distance between the two buildings is about a quarter of a mile (twelve hundred and seventy-five feet). This is covered by a tunnel having at one end a terminus in the basement almost immediately beneath the Distributing Desk, and at the other end in a room in the Capitol about midway between the Senate and House of Representatives. The tunnel is built of brick, is perfectly dry, and about six feet high and four feet wide, or just large enough for a man to enter and make any needed repairs. An endless cable, kept moving by a similar force to that which supplies the apparatus connecting with the stacks, carries two trays back and forth between the terminals, receiving and delivering books by the same arrangement of teeth as has just been described. The trays are much larger, however, than the others, and are capable of containing the largest volumes, such as bound volumes of newspapers. The speed at which the cable runs is about six hundred feet a minute, delivering a book at the Capitol within three minutes after it has left the Library. In addition to the book-carrier, the tunnel contains the pneumatic tube already spoken of, and the wires of private telephones connecting the two Houses of Congress with the Distributing Desk. So quickly can a message be sent and a book returned, that it is said that a Congressman can get the volumes he desires in less time than it would have taken him when the Library occupied its old quarters in the Capitol itself. THE BOOK-STACKS. From the point of view of library equipment and management, however, the three great book-stacks radiating from the Rotunda are the most interesting and remarkable feature of the building. They were entirely planned by Mr. Bernard R. Green, the engineer in charge of the construction of the Library. The word “planned,” indeed, is hardly adequate; “invented” would be nearer the exact fact. The idea of a book-stack, as distinguished from a mere arrangement of bookcases, is so new that such examples as were in existence when Mr. Green entered upon the work were imperfect in many very important points. [Illustration: PLATO. BY JOHN J. BOYLE.]