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.