Double possessives

Question

I am confused with one question. I've been self-studying English for several time. But I've thought about does possessives have sneaky apects. Some days ago I faced with double possessive so I made decision to find out more information about them. I've found one explanation:

"When you’re talking about inanimate objects—objects that aren’t alive, such as “the United Kingdom”—you can’t use a double possessive. According to The New Fowler's Modern English Usage, for a double possessive to be legal, the object of the preposition “of” has to be “definite and human.” In other words, it’s fine to say, “a friend of my uncle’s” but not “a friend of the museum’s.” You have to say, “a friend of the museum.” However, according to this rule, it would be OK to say, “He's a friend of a friend’s,” but we’ve all heard the common expression “a friend of a friend.” I guess double possessives don’t always work".

Why people use this kind of grammar strucure. And when is it necessary to use double possesssives? I've cleared this question up slightly by making a little research:

"For example, if you attempt to avoid the double possessive and say something like "This is Marie's portrait," you end up with an ambiguous sentence that could mean you are looking at a portrait of Marie or a portrait that is owned by Marie. You can fix the problem by substituting one of two sentences depending on what you mean. If you mean Marie owns the portrait, then the double possessive makes it clear: "This is a portrait of Marie's." On the other hand, if it is a lovely rendering of Marie, "This is a portrait of Marie" will serve you well".

Additionally, natives never use it in formal conversation. Are there any other aspets to clarify? For instance, if we are talking about thing which belongs to my friend we might say:

1. This is a book of my friend.
2. This is my friend's book.
3. This is a book of my friend's.

But native would never say:

1. This is a book of the .... University library's.

Am I right?

Answer 1

Actually, English is more flexible than the definition you quote from 'New Fowler's'.

You can impute possession to any object, even if the possessor is not human, but this normaly is not done because describing posession is normaly done only in a legalistic way, and in (human) law, humans have ownership but animals and inanimate objects don't.

Modern useage has moved beyond that; corporations (which are not human) can own things too, so any organization that could be seen as or described as a corporation (such as a library, a museum, a bank, a charity, or a government) could all technically be a possesor under this view.

And beyond that, you can imply possession by something even if in law it has no ability to own something else. For example, I can talk about my brother's wife's dog's toy. The dog may not have any standing in law, but the dog may still consider the toy 'hers'.

English can also be used in unusual ways for artistic purposes. You might write a poem about the fleas which own (live on) the cat who owns you (lives in your house). You would be the flea's cat's servant, who lives to provide food for the cat, who in turn provides blood to the fleas.