THE PROFESSOR'S PUZZLES
and eight vertical lines, and if you look at them diagonally (both
ways) there are twenty-six other lines. If you run your eye along
all these forty-two lines, you will find no two frogs are anywhere in
a line."
" The puzzle is this. Three of the frogs are supposed to jump
from their present position to three vacant glasses, so that in their new
relative positions still no two frogs shall be in a line. What are the
jumps made ? "
" I suppose " began Hawkhurst.
" I know what you are going to ask," anticipated the Professor.
" No, the frogs do not exchange positions, but each of the three
jumps to a glass that was not previously occupied."
" But surely there must be scores of solutions ? " I said.
" I shall be very glad if you can find them," replied the Professor
with a dry smile. " I only know of one—or rather two, counting a
reversal, which occurs in consequence of the position being
symmetrical."
70.—
Romeo and Juliet.
For some time we tried to make those little reptiles perform the
feat allotted to them, and failed. The Professor, however, would
not give away his solution, but said he would instead introduce
to us a little thing that is childishly simple when you have once seen
it, but cannot be mastered by everybody at the very first attempt.
" Waiter !" he called again. " Just take away these glasses,
please, and bring the chessboards."
" I hope to goodness," exclaimed Grigsby, " you are not going
to show us some of those awful chess problems of yours. * White
to mate Black in 427 moves without moving his pieces.' ' The
bishop rooks the king, and pawns his Giuoco Piano in half a jiff.'"
"No, it is not chess. You see these two snails. They are
Romeo and Juliet. Juliet is on her balcony waiting the arrival of
her love, but Romeo has been dining and forgets, for the life of him,
the number of her house. The squares represent sixty-four houses,
and the amorous swain visits every house once and only once before
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