VMS Help PASCAL, Predeclared Routines, Arithmetic, LN  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The LN function returns a real value that represents the natural
  logarithm of the specified parameter.

  Syntax:

     LN( x )

  The parameter 'x' can be an integer or REAL type.  The value  of
  'x' must be greater than zero.