"Solomon," said Frank, slowly and distinctly, "I wish you to find the numbers seven and eleven, add them together, and indicate the sum acquired."
"That's getting into pretty deep water," whispered somebody.
Straight up the side of the board ran the fly, stopping on the figure seven.
"All right so far," assured Merry. "Go ahead."
The fly paused a moment, and then crept downward to the left till it rested on the eleven, where it stopped again.
There was a great hush of expectancy.
"Seven and eleven," said Frank. "That is correct. Added together, seven and eleven make how many?"
The fly slowly faced in several different directions, and then it seemed to hop down one square, alighting on the eighteen!
It was not surprising that the audience burst into such a round of applause as had not been previously heard that evening.
Smiling triumphantly, Frank bowed in graceful acknowledgment.