"parse.grid.list"<- function( grid.list, order.variables="xy"){
#
# utility to find the x and y sequences in grid.list
# this is used in predict.surface and as.surface
#
 M<- length( grid.list)
  unlist(lapply( grid.list, FUN=length))-> gcounts
  xy<- (1:M)[ gcounts> 1]

   if( length(xy)>2){
     stop("only two components of the grid list
                  can have more than one element")}
#
# swap the roles of x and y 

   if( order.variables=="yx") {
         xy<- xy[2:1]}
#
#
# here is the good stuff 
#    
   nx<- gcounts[xy[1]]
   ny<- gcounts[xy[2]]
   x<- grid.list[[ xy[1] ]]
   y<- grid.list[[ xy[2] ]]
#
#  extract the names of the x and y components of the
#  list
#
   xlab<- names( grid.list)[ xy[1] ]
   ylab<- names( grid.list)[ xy[2] ]
   xlab<- ifelse( is.null( xlab), "X", xlab)
   ylab<- ifelse( is.null( ylab), "Y", ylab)

    list( x=x, y=y, nx=nx, ny=ny, xlab=xlab, ylab=ylab, xy=xy)

}