No. CXII
When you have told someone to think of a number between 5 and 15, and while you are not looking, to count upwards from the lowest card step, and round in the direction indicated by the arrow, until that number is reached, and then, starting afresh with “one” on that card to count backwards round the semi-circle, this time not including the central upright or the steps below it, until the number thought of is again reached, you can tell at once which is the final card arrived at, for it will be as many places upwards on the left as there are step cards and their upright.
Thus if there are 3 steps, it must always be the fourth card upwards on the left of the semi-circle. To keep up the puzzle, the number of steps should each time be changed, on the pretext that their number does not signify.
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