In the PLURAL number, when the nominative plural ends in "s," the
possessive case is formed by adding an apostrophe alone ('). If the
nominative plural does not end in "s," an apostrophe and an "s" ('s) are
both added, as in the singular: as, "_Men's_ and _boys'_ shoes."

The possessive case of COMPOUND nouns and expressions used as compound
nouns is formed by adding the proper sign of the possessive to the end of
the compound: as, "That is my _sister-in-law's_ pony," "This is the
_Prince of Wales's_ palace."

[10] "Foundations," pp. 41-43.


EXERCISE VII.[11]

1. _Write the possessive case, singular and plural, of:_ Actor, king,
fairy, calf, child, goose, lady, monkey, mouse, ox, woman, deer, eagle,
princess, elephant, man, witness, prince, fox, farmer, countess, mouth,
horse, day, year, lion, wolf, thief, Englishman.
2. _Write the possessive case of:_ James, Dickens, his sister Mary,
Miss Austen, the Prince of Wales, Frederick the Great, Harper and
Brothers, father-in-law, Charles, Jones, William the Conqueror,
Henry the Eighth, man-of-war, Douglas, Eggleston and Company.

USE and MISUSE of the POSSESSIVE CASE.[12]--It is
sometimes a question whether to use the possessive form or the
preposition _of_. "As a general rule, the possessive case should
be confined to cases of possession."[13]