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 of the chain after theoperation of any one of the safety 
      The books are placed on the carriers by the attendants 
as they pass the openings without stopping,but they are 
automatically removed from the carriersat the delivery station 
and deposited in a receptacle in frontof the opening. If the 
receptacle becomes filled, the conveyorstops automatically 
until the receptacle is emptied, afterwhich it can be started 
      Books can be carried from the stack to the delivery desk 
only; they cannot be returned to thestack.


      This system was installed to carry call slips, messages, 
etc., between the delivery desk, thecall slip file, the attendants' 
desks in the reading rooms, and theattendants' stations 
in the stack.
      From the delivery desk tubes run to the call slip file, to 
four reading rooms, to four pointsin the work space, and to 
the Librarian's office. The returntubes from all these stations
terminate in the basement below thedelivery desk. The 
carriers are discharged onto a beltconveyor by which they 
are brought up to a receptacle in thedelivery desk near the 
attendant's place. Tubes from the callslip file run to the 
Main Reading Room and to one pointon each stack floor,
with a return tube from each point.
      All tubes are of brass, 2 1/4 inches in diameter. The 
carriers are small and of the closedtype. They are moved by 
exhausting the air from the systemby motor driven exhausters, 
of which there are two, each beingof sufficient capacity 
to operate the system.


       The heating and ventilating apparatusfor the building 
was designed to meet local climatic conditions and three

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