Polarities:

Run 1 to run 3
  The top of each main pancake is +.  The top of the end pancake is +.
The field direction is away from the square end pole (+z) for all
pancakes.

Run 3 to run end
  The wiring of the solenoid is complete now and is done according to 
the diagram in this directory.  The field direction is toward the square
end pole.