The example is when you might be reading a certain paper, and the authors refer to another paper. You can't get that other paper as it's unpublished, or it's in a language that you can't read, or maybe something else.
My guess is:
Featherstone et al 1900 (in Thomas and Cullen 2002).
And how is it to be handled in the bibliography?
If you are using a quote from author A that author B is citing, you would go ahead and use the quote from author A and cite it like this:
Blah blah, blahblahblah, blah blah blah-blah blah (qtd. in Author B 65).