function cooling ( step_max )

  for step = 0 : step_max

    if ( step == 0 )
      k = 4;
      [ X, Y ] = temperature_grid ( k );
      T = temperature2 ( X, Y );
    else
      T = cooling ( T );
    end

    tmin = min ( min ( T ) );
    tmax = max ( max ( T ) );
    fprintf ( 'Step %2d, %g <= T <= %g\n', step, tmin, tmax );
    
  end

  return
end
