 the first time step being
appended, Ferret inserts a void point whose bounds are the upper bound of the last time
in the file, and the lower bound of the first time step being appended.  Append
steps 10:12 to the file, and then look at the variable and its coordinates:

<PRE>
   yes? SAVE/APPEND/FILE=bnds.nc/L=10:12 v

   yes? CANCEL VAR v
   yes? USE bnds.nc
   yes? LIST v, TBOXLO[gt=v], TBOXHI[gt=v], TBOX[gt=v]

             DATA SET: ./bnds.nc
             TIME: 01-JAN      00:00 to 31-DEC      05:49
 C