Why is a Raven like a Writing Desk?

a poem has been written on it.


I'm sitting here with a cup of tea looking out the kitchen window at the rainy world, watching a black bird up in the autumn coloured trees and thinking of Poe while this line from Alice in Wonderland is going through my head. This riddle troubled me greatly as a child. I must admit I've never actually read the book and don't know whether it even appears in it, where it's from, or whether any answer is ever given. but in any case this answer finally formed itself in my head now and I was reflecting on the fact that it working depends on the use of the word 'on' in English, and that it probably wouldn't translate well to some other languages.