The moment Alice appeared, she was appealed to by all three to settle the question, and they repeated their argument to her, though, as they all spoke at once, she found it very hard to make out exactly what they said.
MAY 8 . Holmes has already acquired quite a reputation on board as a chess detective! He is much talked about, and our next adventure, a rather humorous one, only added to his fame.
We came across a deserted game, with several players standing about arguing whether Black could or could not castle.
One of the observers argued that Black could castle on the king's side but not on the queen's; another, that Black could castle on the queen's side but not on the king's; a third, that he could not castle at all. Now, each of the three observers had been present at certain stages of the play, but none had been present during the entire game. Thus, each one had remembered different facts which he used in support of his argument.
At Holmes's approach, all three rushed up to him to settle the argument. As all three stated their cases simultaneously, Holmes and I found it a bit difficult to make out exactly what they said. But after the confusion subsided somewhat, Holmes was able to extract the following data concerning the history of the game:
1 White gave Black odds of a rook.
2 White has not yet moved either knight.
3 No promotions have been made.
4 White's last move was pawn from e2 to e4.
Armed with these facts, Holmes studied the position anew. After a while Holmes said to the three disputants, "Gentlemen, all of you are wrong! Assuming you have reported these four facts correctly, it would follow that Black can castle on either side—though it is not his move now. But after White's next move, Black can castle on either side."
"This can be proved?" asked one of the three in astonishment.
"Why, yes," replied Holmes.
"It can be proved that Black can castle?" the disputant repeated incredulously.
"This is truly remarkable, Mr. Holmes. I have known many positions in which it can be proved that a given side can't castle, but I have never before come across a situation in which it can be proved that it can."
"Neither have I," replied Holmes.
"What puzzles me," continued the disputant, "is this: I
can see how to prove that a king or rook has moved, but I cannot for the life of me see how it can be proved that it hasn't moved."
"In this case the proof is quite elementary," replied Holmes.
Can you see how to prove it?
Was this article helpful?