TYPE,PRIVATE :: Pt_field 
    TYPE (field),POINTER :: Pt
    LOGICAL               :: owned
  END TYPE Pt_field

  TYPE vector_field
  
    TYPE (Pt_field), POINTER, DIMENSION(:) :: at => NULL()
    INTEGER :: size
    
    INTEGER :: size_max
    REAL    :: grow_factor
    INTEGER :: chunk
  
  END TYPE vector_field