@translatorcz,
These are difficult questions, and I would be interested to see the views of (qualified) others.
I think that
Quote:What did it turn out to be but a Pearl that by some chance had been lost in the yard" is a question,
is correct, it is a question of sorts, but can also bee seen as a declaration.
It can be simplified as "it turned out to be a pearl that by some chance had been lost in the yard".
The other one is just the same, it is a question as written, but it could be simplified as " He saw a lamb which was just beginning to drink, lower down".
So I think the author is justified in writing either on with a full stop or a question mark.
I think I personally would treat both as a statement, and write them both without a question mark, since the statements "it turned out to be a pearl" and "he saw a lamb" seem to be the most important parts of the sentences.