SHERLOCK HOLMES AND DR. WATSON IN A HOT-AIR BALLOON

Sherlock Holmes and Dr. Watson
are taking a trip across a desert
by hot-air balloon. There are not
many landmarks; so eventually, they become lost. Luckily, while
flying quite low, they see a man.
Holmes shouts, "Sir, could you
please tell me where we are?"
The man looks up, ponders for a
moment, and then answers, "Gentlemen, you are in a hot-air
balloon!"
At this moment, a burst of wind
picks up the balloon and carries it
away.
Holmes turns to Watson and asks: "My friend, do you know who that
man is?"
"No, Holmes, of course not!"
"He's a mathematician!"
"Holmes, that's incredible! But
*how* do you know?" "It's very simple, Watson. First of
all, the man thought before giving
us an answer. Secondly, his
answer was absolutely correct.
And thirdly, the answer he gave
us was of no practical use, whatsoever!"