s mainly because he was so happy in dishing them up in
palatable form.

"You are the man of all others that we were hoping would drop in," said
Hawkhurst. "Have you got anything new?"

"I have always something new," was the reply, uttered with feigned
conceit--for the Professor was really a modest man--"I'm simply glutted
with ideas."

"Where do you get all your notions?" I asked.

"Everywhere, anywhere, during all my waking moments. Indeed, two or three
of my best puzzles have come to me in my dreams."

"Then all the good ideas are not used up?"

"Certainly not. And all the old puzzles are capable of improvement,
embellishment, and extension. Take, for example, magic squares. These
were constructed in India before the Christian era, and introduced into
Europe about the fourteenth century, when they were supposed to possess
certain magical properties that I am afraid they have since lost. Any
child can arrange the numbers one to nine in a square that will add up
fifteen in eight ways; but you will see it can be developed into quite a
new problem if you use coins instead of numbers."

[Illustration]

67.--_The Coinage Puzzle._

He made a rough diagram, and placed a crown and a florin in two of the
divisions, as indicated in the illustration.

"Now," he continued, "place the fewest possible current English coins in
the seven empty divisions, so that each of the three columns, three rows,
and two diagonals shall add up fifteen shillings. Of course, no division
may be without at least one coin, and no two divisions may contain the
same value."

"But how can the coins affect the question?" asked Grigsby.

"That you will find out when you approach the solution."

"I shall do it with numbers first," said Hawkhurst, "and then substitute
coins."

Five minutes later, however, he exclaimed, "Hang it all! I can't help
getting the 2 in a corner. May the florin be moved from its present
position?"

"Certainly not."

"Then I give it up."

But Grigsby and I decided that we would work at it another time, so the
Professor showed Hawkhurst the solution privately, and then went on with
his chat.

68.--_The Postage Stamps Puzzles._

"Now, instead of coins we'll substitute postage-stamps. Take ten current
English stamps, nine of them being all of different values, and the tenth
a duplicate. Stick two of them in one division and one in each of the
others, so that the square shall this time add up ninepenc