conveyor consists of a number of carriers, approximately 16 
inches wide by l2 inches deep, attached to a single chain, the 
distance between carriers being 7 feet. The chain runs over a 
sprocket wheel at the top of a vertical shaft running from the 
top to the basement of the stacks; it is then carried horizontally 
through the basement and up in a housing on the 
first floor back of the delivery desk. The chain runs between 
steel guides in the vertical shafts and on wood-covered steel 
angles through the basement. At each point where a carrier 
is attached to the chain there is a Bakelite roller which carries 
the weight of the carrier on the horizontal runs. The 
chain passes around sprocket wheels wherever it changes 
direction, and an adjustable wheel provides for maintaining 
the proper tension in the chain.
       The sprocket wheel at the top of the vertical shaft in the 
stack is driven through gears by an electric motor of three 
horse-power capacity. The motor speed may be varied so that 
the chain speed may be between 50 and 100 feet per minute. 
The motor may be started only at the motor and at the 
delivery station on the first floor, but if necessary may be 
stopped at any floor in the stack. When the starting button is 
pressed, audible and visible signals are given to warn 
attendants at the various stations that the conveyor is about 
to start, and the actual start of the motor is delayed for several
seconds to give them opportunity to get out of danger.
       At each station there is a large opening without a door 
past which the carriers move and through which they are 
loaded. Suitable devices are placed at the top and bottom of 
each opening so that if an attendant's hands or a book not 
properly placed come in contact with them the motor is 
immediately stopped before any injury can be done to the 
person or book. A device on the driving machine will open the 
control circuit and stop the motor if the chain becomes 
caught in any way, before any damage can be done. There is 
an electric brake which is applied to the motor shaft as soon 
as the current is cut off so that there is very little movement