I was reading Agatha Christie’s The Murder of Roger Ackroyd and noticed following sentence:
About those boots of Ralph Paton’s.
It is really in old (old as in early or mid twentieth century) English that they use apostrophe and of together? Would it not be proper to say:
About those boots of Ralph Paton.
No, you have to use the so-called “double genitive” here:
About those boots of Ralph Paton’s.
It has to be a noun or pronoun in the possessive case, not in the subject case. That’s why it is
a friend of mine
Not
a friend of *me
See other questions with the double-genitive tag for more examples and explanation.