1 OVERLAY
  Syntax: OVERLAY[/option] id [&idb] [symb/col hatch/col patt/col]
      or  OVERLAY[/option] id part
      or  OVERLAY/NEXT [symb/col hatch/col patt/col]
   where: option   can be /SAME|/DIFFERENT|/NEXT/|/NTUPLE|/SMOOTH
          id       is the plot identifier
          idb      is the (optional) secondary identifier
          symb     is the symbol number to use (default = previous + 1)
          hatch    is the hatching to use (default = none)
          patt     is the pattern to use (default = none)
          col      is the (optional) colour for the symbol, hatch or pattern.

  Alias for `HIST OVERLAY'.
  Overlays  a histogram  on the  last one you  plotted. To plot the next
  histogram in memory use the form  `OVERLAY/NEXT'. If  you omit the
  secondary identifier, the default  is used. If you omit the symbol the
  default is taken as 1 greater than the current symbol  number.  If you
  are reading the command from a  macro or `DEFINE'd  command  the symbol
  number must be included on the same line, otherwise the defaults will
  be used. If you give the command interactively, you have to hit `<CR>' to
  get the default values. Hatching  and patterns  only work with the HIGZ
  versions of Mn_Fit  and are  device  dependent
  (see HELP SET HATCH and HELP SET PATTERN for more details).

  You can add the symbol, hatch or pattern colour to the symbol number
  as a qualifier, e.g. `32/red' instead of just 32.

  By  default  the plot  will  have the  same y  scale  as the  last one
  (`/SAME' qualifier).  If you want it on a  different y scale, give the
  command    `OVERLAY/DIFFERENT'.  The new  scale  will be  drawn on the
  right-hand side of the  plot. Give the  command `REDRAW' to get rid of
  the scale on the right from the first plot.

  Use `OVERLAY/NTUPLE' to plot variables from an Ntuple. You have to give
  the command `SET NTUPLE ...' first to specify the variables. Note that
  this form does not apply any cuts and is most useful for plotting
  different columns from a table of entries read in with `DAT_FETCH' for
  example.

2 /SAME

  Default option.
  Specifies that the overlayed plot will have the same y scale as the
  first one.

2 /DIFFERENT

  Specifies that the overlayed plot will have its own y scale drawn
  on the right hand side of the plot.

2 /NEXT

  Draws the next plot that is in memory. Useful for scanning a series of
  plots, following an `id' that you know.

2 /NTUPLE

  Draws the specified variables from an Ntuple. Use the `SET NTUPLE ...'
  command to specify which variables to put on which axis.

2 /SMOOTH

  Draws the plot as a smooth curve using a cubic spline interpolation
  between the points.

